COVERED SHAPE-MEMORY POLYMERIC FIBERS FOR TEXTILE APPLICATIONS

Abstract

The present invention relates to the field of textiles, in particular shape-memory polymeric fibers (SMPF) for textile applications or medical applications where shape fixity and recovery can be kept constant over multiple shape-memory cycles. The present invention relates to a covered shape-memory polymeric fiber (cSMPF) (1) having a core fiber (10) comprising a shape-memory polymer fiber and a substantially unstretchable covering yarn (20) wound around the core fiber (10) in a manner that the maximum engineering strain (.sub.max) of the core shape-memory fiber is reduced to at most the strain at the yield point (.sub.yield) of the uncovered core fiber (10) thus limiting the stretchability or deformation of the core shape-memory fibers and/or textiles and/or fabrics comprising a covered shape-memory fiber during programming or use so as to ensure maximum recoverable strain. Also disclosed is a process for producing a covered shape-memory polymeric fiber (cSMPF) (1), a shape-memory fiber and a shape-memory textile comprising a covered shape-memory polymeric fiber (cSMPF).

Claims

1-23. (canceled)

24. A covered shape-memory polymeric fiber (1) (cSMPF) comprising a core fiber (10), comprising a shape-memory polymer (SMP), and a substantially unstretchable covering yarn (20), characterized in that the substantially unstretchable covering yarn (20) is wound around the core fiber (10) in a manner that the maximum engineering strain of the core fiber (10) is reduced to at most the strain at the yield point of the uncovered core fiber (10).

25. The covered shape-memory polymeric fiber of claim 24, wherein the core fiber (10) comprises a shape-memory polymer (SMP), wherein the shape-memory polymer is a thermally programmable shape-memory polymer, wherein the thermally programmable shape-memory polymer has a programming temperature (Tprog) between 40 C. and 80 C.

26. The covered shape-memory polymeric fiber according to claim 24, wherein the shape-memory polymer (SMP), preferably a thermally programmable shape-memory polymer, is a semi-crystalline shape-memory polymer (SSMP) with a degree of crystallinity between 3% and 70%.

27. The covered shape-memory polymeric fiber according to claim 26, wherein the semi-crystalline shape-memory polymer (SSMP) is selected from the list comprising semi-crystalline polyesters, ethylene-co-monomer-polymers, di-or multi-block-co-polymers, or semi-crystalline ionomers.

28. The covered shape-memory polymeric fiber according to claim 24, wherein the core fiber (10) is selected from a shape-memory polymer selected from the group of polycaprolactone, poly[ethylene-co-vinyl acetate] (PEVA), poly(ethylene-1-octene), polycyclooctene containing trans-polyocentamer (PCO/TOR), poly[ethylene-co-ethyl acrylate-co-maleic anhydride] (PEEAMA), poly[ethylene-co-(methyl acrylate)-co-(glycidyl methacrylate)] (PEMAGMA), perfluorosulphonic acid ionomer (PFSA), amorphous multi block cycloaliphatic polyetherurethane (PEU) consisting of poly(tetramethylene glycol) (PTMEG), 1,4 butanediol (1,4-BD) and methylene bis(p-cyclohexyl isocyanate) (H12MDI).

29. The covered shape-memory polymeric fiber of claim 28, wherein the shape-memory polymer comprises poly[ethylene-co-vinyl acetate] (PEVA), wherein poly[ethylene-co-vinyl acetate] is formed from poly[ethylene-co-vinyl acetate] polymer (PEVAP), wherein the vinyl acetate content in the poly[ethylene-co-vinyl acetate] polymer is between 5% and 50% of the total weight of the polymer.

30. The covered shape-memory polymeric fiber according to claim 24, wherein the covering yarn (20) is selected from cotton, wool, silk, linen, viscose, acrylic, nylon and polyester.

31. The covered shape-memory polymeric fiber according to claim 24, wherein the covered shape-memory polymeric fiber has a stretchability from 30 to 1000%.

32. The covered shape-memory polymeric fiber according to claim 24, wherein the covering yarn (20) is wound around the core fiber (10) with a rate of 500 to 6000 twists per meter.

33. The covered shape-memory polymeric fiber according to claim 24, wherein the core fiber (10) is a multifilament fiber, preferably with a linear fiber density between 15 and 1000 dtex.

34. The covered shape-memory polymeric fiber according to claim 24, wherein the diameter ratio between the covering yarn and core fiber lies preferably within 1:1 to 1:20.

35. The covered shape-memory polymeric fiber according to claim 24, wherein the diameter of the core fiber lies within 50-500 m.

36. (canceled)

37. A method for producing the covered shape-memory polymeric fiber (cSMPF) of claim 24, including the steps of a) extruding a core fiber (10), of a core fiber precursor for a shape-memory polymer according to claim 24, preferably with a cross-linker or cross-linking agent, b) curing the extruded fiber, preferably under UV, beta or gamma radiation for covalent cross-linking, then c) winding a covering yarn (20) around the core fiber (10).

38. A shape-memory fabric, comprising a covered shape-memory polymeric fiber (cSMPF) comprising a core fiber (10), and a substantially unstretchable covering yarn (20) according to claim 24, wherein the covered shape-memory polymeric fiber (cSMPF) is arranged in a) a shape-memory mesh network of interwoven or intertwined cSMPFs, forming an operatively connected structure, and/or b) a shape-memory inlay, arranged in a second fabric, characterized in that the maximum engineering strain of the core fiber (10), is reduced to at most the strain at the yield point of the uncovered core fiber (10).

39. The shape-memory fabric of claim 38 as a thermally programmable textile, such as a technical, medical, orthopedic, industrial, sports or leisure thermally programmable textile, comprising the shape-memory textile of claim 38

40. (canceled)

41. (canceled)

42. A shape-memory textile comprising a covered shape-memory polymeric fiber (cSMPF) according to claim 24 and at least a further fabric and/or a further fiber, wherein the cSMPF is arranged in and/or on the shape-memory textile by knitting, weaving, braiding, embroidery, composite techniques or as 3D textile structure, characterized in that the maximum engineering strain of the core fiber (10) is reduced to at most the strain at the yield point of the uncovered core fiber (10).

43. The shape-memory fabric of claim 42 as a thermally programmable textile, such as a technical, medical, orthopedic, industrial, sports or leisure thermally programmable textile, comprising the shape-memory textile of claim 42.

44. (canceled)

45. (canceled)

Description

DETAILED DESCRIPTION

Covered Shape-Memory Polymeric Fiber (cSMPF)

[0022] The present invention relates to a covered shape-memory polymeric fiber (cSMPF) having a core fiber, and a substantially unstretchable covering yarn wound around the core fiber in a manner that the maximum engineering strain of the core fiber is reduced to at most the strain at the yield point of the uncovered core fiber.

[0023] In the context of the present invention, have/having may be used synonymously or interchangeably with the terms comprising or consisting of and means that a feature comprises or consists of a particular sub-feature.

[0024] In some further preferred embodiments, the invention relates to a covered shape-memory polymeric fiber (cSMPF) (1) comprising or consisting of at least [0025] a core fiber (10), comprising or consisting of a shape-memory polymer (SMP), and [0026] a substantially unstretchable covering yarn (20),
wherein the substantially unstretchable covering yarn (20) is wound around the core fiber (10) in a manner that the maximum engineering strain of the core fiber (10) comprised by the covered shape-memory polymeric fiber (1) is reduced to at most the strain at the yield point of the uncovered core fiber (10).

[0027] In a further preferred embodiment, the invention comprises a covered shape-memory polymeric fiber (cSMPF) (1) comprising or consisting of at least [0028] a core fiber (10), comprising or consisting of a shape-memory polymer, and [0029] a substantially unstretchable covering yarn (20) wound around the core fiber (10),
wherein the maximum engineering strain (.sub.max) of the core fiber (10) comprised by the covered shape-memory polymeric fiber (1) is limited to at most the strain at the yield point (.sub.yield) of the uncovered core fiber (10), preferably determined at 25 C., wherein the strain at the yield point (.sub.yield) is preferably in the range between 10% and 100%, more preferably between 15% and 70%, most preferably between 20% and 60% This has the advantage that cSMPFs exhibit consistent shape stability and recovery over multiple shape memory cycles and ensure a wide stretchability range while maintaining shape memory properties. This is critical for a wide range of textile applications where precise and reliable performance is required.

[0030] In some preferred embodiments, the maximum engineering strain (.sub.max) of the core fiber (10) comprised by the covered shape-memory polymeric fiber (1) is limited to at most the strain at the yield point (.sub.yield) of the uncovered core fiber (10), preferably determined at 25 C., wherein the strain at the yield point (.sub.yield) is in the numerical range obtained by combining any two of the following end point values: 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 40%, 45%, 50%, 52%, 54%, 56%, 58%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%.

[0031] A core fiber (10) (also referred to as core shape-memory fiber (10)) in the context of the current invention comprises or consists of a shape-memory polymer and may be covered by a substantially unstretchable covering yarn (20) wound around the core fiber (10). In this context, the maximum engineering strain (.sub.max) of the core fiber (10) is equivalent to the maximum engineering strain (.sub.max) of the covered shape-memory polymeric fiber (cSMPF) comprising the core fiber (10).

[0032] An uncovered core fiber (10) (sometimes referred to as core fiber (10)) in the context of the current invention comprises or consists of a shape-memory polymer without a substantially unstretchable covering yarn (20) wound around the core fiber (10). Therefore the strain at the yield point (.sub.yield) of the uncovered core fiber (10) is equivalent to the yield point of the core fiber (10) of a covered shape-memory polymeric fiber (cSMPF) without a substantially unstretchable covering yarn (20).

[0033] A fiber in the context of this invention is a single continuous strand of a material, a form in which it is much longer in one axial direction than in 2 others comparably small directions.

[0034] A filament according to the current invention may be a monofilament, which corresponds to a fiber in the spirit of the current invention, or a multifilament, which comprises at least a fiber in the spirit of the current invention. A multifilament is a bundle of co-directed fibers that in some preferred embodiments are filament fibers, i.e. fibers whose length is comparable to the length of the multifilament (common example rope, cable, synthetic textile yarns), or in another preferred embodiment are staple fibers, i.e. fibers whose length is significantly shorter than the length of the whole multifilament (common example cotton, wool yarns).

[0035] In one aspect, the present invention relates to a covered shape-memory polymeric fiber (cSMPF) having a core fiber of semi-crystalline polymer fibers and a substantially unstretchable covering yarn wound around the core fiber in a manner that the maximum engineering strain (.sub.max) of the core shape-memory fiber is reduced to at most the strain at the yield point (.sub.yield) of the uncovered core fiber. Thus, the covering yarn is used to limit the stretchability or deformation of the core shape-memory fibers during programming so as to ensure maximum recoverable strain. The maximum deformation of the core fiber of a given length (L.sub.0) and diameter (D.sub.0) in the unstretched state by covering the fiber with a covering yarn can be influenced by the density of entwining (also preferably referred to as density of covering) (.sub.0) of the core fiber in the unstretched state, i.e. by the number of twists per meter of the covering yarn when the core fiber is in the unstretched state, and the length (I) and diameter (d) of the covering yarn, all in relation to the diameter of the core fiber (D.sub.0) in the unstretched state.

[0036] Upon applying a stress to the covered fiber so as to stretch the fiber, the length (L.sub.1) of the core fiber increases, whereas the density of entwining (.sub.1) decreases. The strain () of the core fiber is given by the following formula:

[00001]${}_1=\frac{L_1-L_0}{L_0}100\%,$

wherein .sub.1 is the strain, L.sub.1 is the length of the core fiber at said stress, L.sub.0 is the length of the core fiber in the unstretched state.

[0037] In the context of this invention, stress and strain can be used interchangeably, because the deformation of the SMPF is limited to its yield point and/or elastic limit. In this ranges, each strain value may correspond to one stress value. This is why each point on the stress-strain curve of SMPF may be used to unambiguously defined with either stress or strain value.

[0038] Stretching (elongation) of the core fiber having the covering yarn wound around it causes the pitch (r), i.e. the distance between two loops of the twist, of the covering yarn around the core fiber to increase from r.sub.0 to r.sub.1, whereby the density of entwining (.sub.1) decreases. The covering yarn is not stretched until up to a maximum strain (.sub.max) of the core fiber. Further stretching of the core fiber beyond the maximum strain (.sub.max) would require stretching of the covering yarn as well. Under the premise that the covering yarn is substantially unstretchable, stretching the fiber beyond the point of maximum strain (.sub.max) would cause a steep increase in the force required for further stretching or deformation, after this point, the force exerted by the covering yarn on the core fiber increases, potentially crushing and damaging the core fiber until finally a rupture of the covering yarn will occur.

[0039] According to the present invention, this point of maximum strain (.sub.max) of the core fiber should be chosen so as to not exceed the strain at the yield point (.sub.yield) of the core fiber. According to some embodiments, the point of maximum strain (.sub.max) is independent of the material of the covering yarn, and solely dependent on the diameter (D.sub.0) of the shape-memory polymeric core fiber (cSMPF), the diameter of the covering yarn (d) and the density of entwining (.sub.0), wherein the density of entwining (.sub.0) is defined as:

[00002]${}_0=\frac{n_0}{L_0}$

wherein .sub.0 is the density of entwining, L.sub.0 is the length of the core fiber in the unstretched state and n.sub.0 is the number of windings of the covering yarn around the core fiber in the unstretched state.

[0040] According to some preferred embodiments of the invention, the strain at the yield point of the shape-memory polymeric core fiber (cSMPF) is dependent on the material of the core fiber, particularly the shape-memory-polymer comprised by the core fiber, and the diameter (Do) of the core fiber, while being limited by accordingly selecting the diameter of the covering yarn (d) and the density of entwining (.sub.0) and the material of the covering yarn so that the maximum strain (.sub.max) of the core fiber, determined by the material and diameter of the core fiber, should be chosen so as to not exceed the strain at the yield point (.sub.yield) of the core fiber.

[0041] The length of the covering yarn, dependent on the length of the core fiber, required to achieve that the maximum engineering strain (.sub.max) of the core shape-memory fiber is reduced to at most the strain at the yield point (.sub.yield) of the uncovered core fiber can be determined according to the following equation:

[00003]$l_{}=L_0=\sqrt{\left(1+\frac{{}^2{}_0^2{D}_0^2}{4}\right){}_{\max }^2+\left(2-{}^2{}_0^{2}d-{}^2{}_0^2{D}_0^2\right){}_{\max }+\left(1+{}^2{{}_0^2\left(D_0+d\right)}^2\right)}$

wherein L.sub.0 is the length of the core fiber in the unstretched state, D.sub.0 is the diameter of the core fiber in the unstretched state, po is the density of entwining in the unstretched state, d is the diameter of the covering yarn, and .sub.max is the strain of the core fiber at its yield point.

[0042] The covering yarn may be wound around the core fiber as single or double, covering with S or Z-directional twists. The twist density is preferably in a range of 750 to 3000 twists per meter.

[0043] The yield point is the point on a stress-strain curve that indicates the limit of elastic behavior. Thus, the engineering strain at the yield point (.sub.yield) is the strain (elongation) the core fiber can sustain without being permanently deformed. The yield point is a material characteristic value and can be determined according to ISO 527.

[0044] In particular preferred embodiments of the invention, the yield point is corresponding to the elastic limit, which is the point on a stress-strain curve that indicates the limit of elastic behavior. Most preferably, the engineering strain at the yield point (.sub.yield) is limited to the strain at the elastic limit. The elastic limit, especially in the context of the shape-memory polymers comprised by the core fiber of the cSMPF of the current invention may be determined by thermomechanical analysis using a tensile testing machine, for example a MTS 858 testing machine equipped with an appropriate indirect temperature measurement system, preferably a IR camera, for example a ThermaCam Phoenix. An exemplary procedure is described in Experimental and numerical investigation of yielding phenomena in a shape memory polymer subjected to cyclic tension at various strain rates (E. A. Pieczyska, M. Staszczak, K. Kowalczyk-Gajewska, M. Maj, K. Golasiski, S. Golba, H. Tobushi, S. Hayashi, Polymer Testing, Volume 60, 2017, Pages 333-342, ISSN 0142-9418, https://doi.org/10.1016/j.polymertesting.2017.04.014), The importance of distinguishing between elastic and plastic deformation regions lies in understanding the material's behavior under stress. The elastic regime indicates reversible deformation, whereas the plastic regime signifies permanent deformation. The yield point, closely related to the elastic limit, marks the transition from elastic to plastic behavior, indicating the maximum strain the SMP can withstand without undergoing permanent deformation. Limiting the engineering strain (.sub.max) to the yield point (.sub.yield) or to the elastic limit is therefore important for ensuring a high shape recovery ratio and the mechanical stability of the shape-memory effect against strain.

[0045] Elastic limit can be determined with a step-cycle test described and performed in Strain recovery and stress relaxation behaviour of multiblock copolymer blends physically cross-linked with PLA stereocomplexation Izraylit, V., Heuchel, M., Gould, O. E., Kratz, K., & Lendlein, A. (2020). Polymer, 209, 122984. https://doi.org/10.1016/j.polymer.2020.122984. Here, the elastic limit is determined with a step-cycle test. A sample was stretched to a certain strain with a constant extension rate. Then, the stress was removed to 0 at the same contraction rate. At each following step the sample was elongated to a higher strain than at the previous one. The cycles were continued until sample rupture. The recovered strain is considered to be the elastic component .sub.e of the deformation, while remaining is the plastic component .sub.p of the deformation. Elastic limit can be determined a point of sharp increase of the tangent of the .sub.p() where is the stress value at the stress-strain curve at deformation related to .sub.p in the particular step in the step-cycle experiment. In the same work, the yield point is defined as a point of the maximum curvature of the stress-strain curve in the region of elastic limit. Preferably, the differences between those points may be neglected in practical applications.

[0046] The expression substantially unstretchable means that the covering yarn is stiffer in relation to the core fiber. This ratio can be quantified with Young's modulus. Young's modulus is a mechanical property that measures the compressive stiffness, in this context particularly tensile stiffness, of a solid material when force is applied lengthwise. In an embodiment of the invention, the covering yarn has higher Young's modulus than the core fiber. In another embodiment of the invention, the Young's modulus of the covering yarn is at least twice, preferably at least three times, most preferably at least five times of the Young's modulus of the of the core fiber.

[0047] In another embodiment, the ratio of the diameter of the core fiber D.sub.0, the diameter of the covering yarn d, and the density of entwining po are defined in a way that during the stretching of cSMPF exists .sub.onset, at which stretching of covering yarn 20 onsets and the slope of tangent of a stress-strain curve increases in a leap. Other parameters required to determine the ratio of D.sub.0, d and po are the length of the core fiber L, the length of the covering yarn l, the distance between two loops of the twist r, also referred to as pitch, and the number of twists n. L.sub.0 defines the length of the core fiber in an unstretched state and L.sub.1 defines the length of the core fiber 10 in a stretched state. Do defines the diameter of the core fiber 10 in an unstretched state and D.sub.1 defines the diameter of the core fiber 10 in a stretched state. AL is the length change of the core fiber 10, thus L=L.sub.1L.sub.0. D is the diameter change of the core fiber 10, thus D=D.sub.1D.sub.0.

[0048] The engineering strain of the core fiber 10 can then be defined as:

[00004]$=\frac{L_1}{L_0}-1=\frac{L}{L_0}.$

[0049] The Poisson's rate v of the core fiber 10 is defined as:

[00005]$v=\frac{\frac{D}{D_0}}{\frac{L}{L_0}}.$

[0050] The formula of the Poisson's rate v of the core fiber 10 can be rewritten as

[00006]$\frac{D_1}{D_0}=1-v\frac{L}{L_0}=1-v$

[0051] From the formulas just defined, the following dependencies can be derived:

[00007]$$\begin{gathered} D_1=\left(1-v\right), \\ {L}_1=L_0\left(+1\right), \end{gathered}$$

[0052] The engineering strain of the covering yarn .sub.t can be expressed as a function of the engineering strain of the core fiber :

[00008]${}_l={}_l\left(\right)=\frac{l_1-l_0}{l_0}=\frac{l}{l_0}=\frac{l_1}{l_0}-1,$

Wherein l.sub.1 can be defined as:

[00009]$l_1=L_0=\sqrt{\left(1+\frac{{}^2{}_0^2{D}_0^2}{4}\right){}^2+\left(2-{}^2{}_0^2{D}_{0}d-{}^2{}_0^2{D}_0^2\right)+\left(1+{}^2{{}_0^2\left(D_0+d\right)}^2\right)}$

[0053] This formula for the length of the covering yarn 20 in the stretched state l.sub.1 can be derived as follows. First, the equation for the circumference of the core fiber 10 and the covering yarn 20 is established. Since the covering yarn 20 is wound in spirals around the core fiber 10, the number of twists n is multiplied by the distance between two twists in the stretched state r.sub.1 and added to the circumference.

[00010]$l_1^2={}^2{n^2\left(D_1+d\right)}^2+r_1^2{n}^2$

[0054] For n and D.sub.1, the formulas already established above are used and instead of

[00011]$r_1^2{n}^2$

the parameter

[00012]$L_1^2$

is used

[00013]$l_1^2=L_0^2{}_0^2{{}^2\left(D_0\left(1-v\right)+d\right)}^2+L_1^2$

[0055] Now the formula obtained above is used for L.sub.1 and the equation is brought into the form of a quadratic equation.

[00014]$\begin{array}{c}{l}_1^2=L_0^2{}_0^2{}^2\left(D_0^2-2D_0^{2}v+D_0^2{v}^2{}^3+2D_{0}d-2D_0\mathrm{dv}+d^2\right)+L_0^2+2L_0^2+{}^2{L}_0^2\\ =L_0^2\left(\left(1+{}^2{v}^2{}_0^2{D}_0^2\right){}^2+\left(2-2{}^{2}v{}_0^2{D}_{0}d-2{}^{2}v{}_0^2{D}_0^2\right)+\left(1+{}^2{{}_0^2\left(D_0+d\right)}^2\right)\right)\end{array}$

[0056] For the selected materials the is limited with elastic limit, which means that elongation can be considered elastic. Therefore, no major structural reorganization takes place at molecular level. From this follows that a constant volume can be assumed, so that the Poisson's ratio can be assumed as =0.5. This leads to the formula:

[00015]$\begin{array}{c}{l}_1=l\left(\right)\\ =L_0\sqrt{\left(1+\frac{{}^2{}_0^2{D}_0^2}{4}\right){}^2+\left(2-{}^2{}_0^2{D}_{0}d-{}^2{}_0^2{D}_0^2\right)+\left(1+{}^2{{}_0^2\left(D_0+d\right)}^2\right)}\end{array}$

[0057] For l.sub.0 the following formula is obtained:

[00016]$\begin{array}{c}{l}_0^2={}^2{n^2\left(D_0+d\right)}^2+r_0^2{n}^2\\ ={}^2{L}_0^2{{}_0^2\left(D_0+d\right)}^2+L_0^2\\ =L_0^2\left({}^2{{}_0^2\left(D_0+d\right)}^2+1\right)\\ l_0=L_0\sqrt{1+{}^2{{}_0^2\left(D_0+d\right)}^2}\end{array}$

[0058] The .sub.onset is defined as , at which .sub.l() becomes positive.

[00017]$\begin{array}{c}{}_l={}_l\left(\right)=\frac{l_1}{l_0}-1\\ \frac{((=\sqrt{\left(1+\frac{{}^2{}_0^2{D}_0^2}{4}\right){}^2+\left(2-{}^2{}_0^2{D}_{0}d-{}^2{}_0^2{D}_0^2\right)+(1+{}^2{{}_0^2\left(D_0+d\right)}^2}}{\left(\frac{\sqrt{\left(1+{}^2{{}_0^2\left(D_0+d\right)}^2\right)}}{=\sqrt{1+\frac{\left(2-{}^2{}_0^2{D}_{0}d-{}^2{}_0^2{D}_0^2\right)}{1+{}^2{{}_0^2\left(D_0+d\right)}^2}+\frac{1+{}^2{}_0^2{D}_0^2/4}{1+{}^2{{}_0^2\left(D_0+d\right)}^2}{}^2}-1}\right)}\end{array}-1$

[0059] By following the ratio between D.sub.0, d and .sub.0 the stretching of the core fiber 10 can be avoided by selecting D.sub.0, d and .sub.0, so that l and thus the engineering strain of the covering yarn .sub.l() becomes positive only when the maximum engineering strain (.sub.max) of the core shape-memory fiber 10 is passed.

[0060] Thus the covering yarn 20 is wound around the core fiber 10 in a manner that after stretching to a defined engineering strain (.sub.max), the covering fiber will be so deformed that further stretching of cSMPF will cause axial stretching of the covering yarn. If the core fiber 10 is stretched at a temperature between glass transition and melting temperature defined by ISO 11357 up to the engineering strain (.sub.max) and released, will recover the residual deformation, if heated to a temperature between 25 C. and melting temperature defined by ISO 11357. This particular means that if the cSMPF comprising the core fiber 10 is heated to a temperature between 25 C. and melting temperature defined by ISO 11357, it will recover to =0.

[0061] In some embodiments of the covered shape-memory polymeric fiber according to the invention disclosed herein, the core fiber (10) is selected from a shape-memory polymer (SMP), wherein the shape-memory polymer is a thermally programmable shape-memory polymer SMP, preferably with a crystalline rigid segment and a switching segment, wherein the thermally programmable shape-memory polymer has a programming temperature (T prog) between 4 and 80 C., more preferably between 4 and 70 C., as determined with Differential Scanning calorimetry (DSC).

[0062] In the context of this patent application, Differential Scanning calorimetry (DSC) is defined as an analytical technique used to measure the thermal properties of shape-memory polymers, especially semi-crystalline shape-memory polymers, comprised by covered shape-memory polymeric fibers (cSMPF) utilized in the current invention. DSC is instrumental in determining the thermal transitions of these materials, such as melting temperature, glass transition temperature, and crystallization behavior. This information is crucial for understanding and optimizing the thermal-responsive behavior of the cSMPFs in the proposed compression garments.

[0063] The shape fixity (R.sub.f) and shape recovery (R.sub.r) in a cycle (N) can be calculated from applied deformation (.sub.m) during programming, fixed strain in the temporary shape (.sub.u) after removing stress in the programming step and recovered strain (.sub.p) in the recovery cycle using following equations.

[00018]$\begin{array}{c}{R}_f\left(N\right)=\frac{{}_u\left(N\right)}{{}_m}100\\ R_r\left(N\right)=\frac{{}_u\left(N\right)-{}_p\left(N\right)}{{}_u\left(N-1\right)-{}_p\left(N-1\right)}100\end{array}$

[0064] In some preferred embodiments, the shape-recovery ratio for the covered fibers, especially the covered shape-memory polymeric fibers is between 80% and 100% more preferably between 92.5% and 100%, especially preferably between 95% and 100%. This allows for repeated use in the disclosed applications. In a most preferred embodiment, the shape-recovery ratio for the covered fibers, especially the covered shape-memory polymeric fibers is above 95% to meet the demand of the RAL-387 standard for medical compression garments, especially preferably the class 1 range with a pressure range between 2.4 and 2.8 kPa.

[0065] In order to ensure and evaluate long term shape-memory capability of these fibers, a test with 100 shape-memory cycles was performed which showed identical results for shape-recovery and lower shape fixity ratios over the course of 100 cycles. For practical reasons and in order to reduce the time for one cycle, the heating and cooling rates were 10 cmin.sup.1 here and equilibration times were reduced to 1 min.

[0066] In a preferred embodiment of the covered shape-memory polymeric fiber of the current invention, the thermic programming process comprising [0067] a) An initial programming step, comprising controlled heating of the covered shape-memory polymeric fiber to a specific programming temperature (T.sub.prog) while stretching the fiber at a controlled rate, preferably 10 mm/min, to a predefined programming strain (.sub.prog) below maximum engineering strain, then [0068] b) An equilibration step, comprising holding the stretched state for an equilibration time, preferably between 1 and 10 minutes, followed by [0069] c) A cooling step, comprising cooling the covered shape-memory polymeric fiber to a temperature below its crystallization point, preferably 35 C. while under predefined programming strain (.sub.prog).

[0070] The programming temperature (T.sub.prog), preferably between 4 and 80 C., more preferably between 4 and 70 C., is specific to each embodiment of the coated shape-memory polymer fiber and depends on the properties of the comprehensive shape-memory polymers, such as crystallinity, type of polymer and cross-linking grade. The stretching with the programming strain (.sub.prog) aligns the polymer chains in the direction of the force applied. In some preferred embodiments the programming temperature may be in the numerical range obtained by combining any two of the following end point values: 40 C., 42 C., 44 C., 46 C., 48 C., 50 C., 52 C., 54 C., 56 C., 58 C., 60 C., 62 C., 64 C., 66 C., 68 C., 70 C., 75 C., or 80 C.

[0071] Especially preferably, in the context of a thermally programmable shape-memory textile and/or a shape-memory fabric, the programming temperature is in the range between 40 C. and 70 C., or may alternatively be in the numerical range obtained by combining any two of the following end point values: 40 C., 42 C., 44 C., 46 C., 48 C., 50 C., 52 C., 54 C., 56 C., 58 C., 60 C., 62 C., 64 C., 66 C., 68 C., or 70 C. This allows for a customized programming of the textile or fabric of the invention directly on the body of a subject, which allows a better fitting without the risk of burning the subject.

[0072] In some embodiments related to the covered shape-memory polymeric fiber (cSMPF) of the invention and/or shape-memory textile and/or shape-memory fabric comprising the same, the temperature range is chosen so that the programming and/or shape-recovery can be executed directly on the subject's body. This may advantageously allow the thermal programming and recovery of the covered shape-memory polymeric fiber and/or shape-memory textile and/or shape-memory fabric comprising the same directly to the shape of the subject and realize an optimal force distribution.

[0073] In some preferred embodiments, the shape-memory textile or fabric is programmed according to the contours of a patient's body. This means that the shape-memory textile or fabric is initially set to conform to the patient's specific body shape. After wearing and removal, the programmed shape can be restored. This is particularly useful in medical garments where a custom fit is essential for therapeutic effectiveness.

[0074] An alternate embodiment involves programming the permanent shape of the shape-memory textile or shape-memory fabric at higher temperatures, beyond the typical range of environmental or body temperatures. This ensures that the programmed shape is not inadvertently altered or distorted through everyday activities, such as washing or drying. In this case, the patient does not play a role in the programming process. Instead, the shape-recovery of the garment's shape, if it has been deformed during use, would occur when it is worn by the patient. Such a garment comprising a cSMPF or a shape-memory textile or shape-memory fabric is designed to maintain its therapeutic shape and function regardless of routine handling, ensuring consistency and reliability in medical applications.

[0075] A thermally programmable shape-memory polymer may also be a semi-crystalline shape-memory polymer and vice versa. These two designations refer to two different but related properties of a shape-memory polymer and are not mutually exclusive. In a preferred embodiment, a shape-memory polymer is a thermally programmable semi-crystalline shape-memory polymer.

[0076] In some most preferred embodiments, a shape-memory polymer comprised by the core fiber of the covered shape-memory polymeric fiber (cSMPF) is a semi-crystalline shape-memory polymer (SSMP) with a degree of crystallinity between 3% and 70%, which is thermally programmable and has a programming temperature (T.sub.prog) between 4 and 80 C., which represents a thermally programmable semi-crystalline shape-memory polymer. This has a technical effect that the crystalline properties, which are preferably controlled by the method for making a cSMPF according to the present disclosure and which have a profound effect on the programming temperature, strain, and other parameters of the core fiber, can be modified to achieve the desired programming temperatures essential for use of the cSMPF in garments, shape-memory fabrics and shape-memory textiles, particularly those suitable for thermal programming and recovery on the body of a subject.

[0077] The nature of the covering yarn ranges from yarns of natural fibers, such as cotton, wool, etc., to semi-synthetic or synthetic yarns, such as viscose, acrylic, nylon, polyester, etc. In a further preferred embodiment of the covered shape-memory polymeric fiber according to the current invention the covering yarn is selected from cotton, wool, silk, linen, viscose, acrylic, nylon and polyester.

[0078] In another preferred embodiment of the covered shape-memory polymeric fiber according to the current invention the covering yarn is wound around the core fiber as single or double covering with S or Z direction twists.

[0079] The diameter ratio between the covering yarn and core fiber may preferably range from 1:1 to 1:20. In a further disclosed embodiment of the covered shape-memory polymeric fiber the diameter ratio between the covering yarn and core fiber lies preferably within 1:1 to 1:20. A smaller diameter ratio ensures adequate coverage and protection of the core fiber by the covering yarn, while larger ratios allow for greater flexibility and adaptability of the core fiber within the covering.

[0080] Preferably, the diameter of the core fiber in the cSMPF lies within 50-500 m. In a preferred embodiment of the covered shape-memory polymeric fiber the diameter of the core fiber lies within 50-500 m.

[0081] The covering yarn may be a multifilament or a monofilament yarn. However, monofilament yarns are preferred. In a preferred embodiment of the covered shape-memory polymeric fiber the covering yarn is a monofilament yarn.

[0082] In a preferred embodiment the core fiber (10) is a multifilament fiber, preferably with a linear fiber density value between 15 and 1000 dtex, more preferably between 35 and 600 dtex. A multifilament fiber consists of many fine individual filaments that are collected as a single fiber. This structure may have several advantages, such as increased flexibility, increased strength, and improved rupture resistance. In a preferred embodiment, linear fiber density of the core fiber in the cSMPF is within the numerical range obtained by combining any two of the following end point values: 15 dtex, 20 dtex, 25 dtex, 30 dtex, 35 dtex, 40 dtex, 45 dtex, 50 dtex, 75 dtex, 100 dtex, 150 dtex, 200 dtex, 250 dtex, 300 dtex, 350 dtex, 400 dtex, 450 dtex, 500 dtex, 550 dtex, 600 dtex, 650 dtex, 700 dtex, 750 dtex, 800 dtex, 850 dtex, 900 dtex, 950 dtex, and 1000 dtex.

[0083] In a preferred embodiment related to a shape-memory fabric, the core fiber comprised by the cSMPF is a multifilament fiber with a linear fiber density value between 15 and 75 dtex, more preferably between 20 and 50 dtex. Because of the high density of the cSMPF in a shape-memory fabric according to the current intention, the linear fiber density of the comprised cSMPF is chosen from this range as higher linear fiber densities would lead to a rigid fabric for the uses disclosed herein.

[0084] In an alternatively preferred embodiment related to a shape-memory textile, the core fiber comprised by the cSMPF comprised by the shape-memory textile is a multifilament fiber with a linear fiber density value between 250 and 750 dtex, more preferably between 300 and 600 dtex. Because of the lower amount of the cSMPF fibers in a shape-memory textile according to the current intention, the linear fiber density of the comprised cSMPF is chosen from this range as lower linear fiber densities would lead to a textile with a weak shape-memory effect.

[0085] In the context of fibers, dtex stands for decitex and is a unit of measurement used to express the linear density or fineness of a fiber. It is defined as the mass in grams per 10,000 meters of the fiber.

[0086] The covered shape-memory polymeric fiber according to any one of the previous claims wherein the covering yarn (20) is wound around the core fiber (10) with a rate of 500 to 6000 twists per meter, preferably 750 to 3000 twists per meter. A higher twist rate ensures that the covering yarn is securely wound around the core fiber, providing stability and protection. At the same time, maintaining the twist rate within this range prevents over-constriction of the core fiber, which could otherwise impede its shape-memory functionality.

[0087] The covered shape-memory polymeric fiber according to any one of the previous claims wherein the covered shape-memory polymeric fiber has a stretchability from 30 to 1000%, preferably 50 to 900%. This flexibility in stretchability means the fiber can be used in settings that require either moderate or significant elongation, catering to various functional needs. For instance, higher stretchability might be desired in textiles for sports and leisure, while moderate stretchability could be more suitable for medical or technical applications.

[0088] In some preferred embodiments of the covered shape-memory polymeric fibers (cSMPF), the elongation at break (.sub.break) with error margins is in a range between 500+150% and 1150+150%, preferably between 600+150% and 1000+150%. This allows a large safety margin after stretching the fiber beyond the intended engineering strain according to the invention.

Materials and Shape-Memory Polymers

[0089] A shape-memory polymer in accordance with the current invention is preferably a semi-crystalline polymer with a rigid segment and a switching segment. The rigid segment, also referred to as the hard segment, is the part of the shape-memory polymer that defines the permanent shape of the material by establishing intermolecular interactions. This segment enables the polymer to retain the information of its original shape under various conditions and/or after deformation. The rigid segment can be presented by covalent bonds, molecular entanglement, crystallites, or other molecular interactions. The switching segment of the shape-memory polymer is responsible for the shape-memory behavior of the material. This segment is designed to be responsive to external stimuli, such as temperature changes. When exposed to a specific temperature, also referred to as programming temperature, associated with a phase transition, preferably the glass transition and/or melting temperature, the switching segment becomes flexible, allowing the shape-memory polymer to be temporarily reshaped under a certain programming strain (.sub.prog) at programming temperature (T prog) followed by a defined equilibration time. Upon removal of the stimulus, the segment returns to its original state, governed by the rigid segment, thus reverting the material to its predefined shape. The switching segment can be presented by crystallites, glassy amorphous segments, or other reversible molecular interactions.

[0090] In a preferred embodiment of the covered shape-memory polymeric fiber of the current invention the shape-memory polymer (SMP) is a semi-crystalline shape-memory polymer (SSMP) with a degree of crystallinity between 3% and 70%, more preferably with a degree of crystallinity between 5% and 60%, as determined with wide angle x-ray scattering (WAXS), also referred to as X-ray diffraction spectroscopy (XRD). Alternatively preferably, the degree of crystallinity may be determined with DSC. The degree of crystallinity is an attribute that significantly influences the performance and application of the shape-memory polymer fibers according to the current invention. Specifically, for the semi-crystalline shape-memory polymers (SSMPs) used in the core of these fibers, the degree of crystallinity is directly linked to their shape-memory characteristics and mechanical properties. Importantly, it influences the phase transition temperatures associated with the programming of a covered shape-memory polymeric fiber. Preferably, a semi-crystalline shape-memory polymer is also thermally programmable with degree of crystallinity as an indicator of the molecular structure, more specific content of the switching segment in shape-memory polymer, which influence the phase transition temperature and shape fixity associated with the thermal programming of the shape-memory polymer and its shape-memory performance.

[0091] The degree of crystallinity in the context of this invention is defined as the proportion of the polymer's structure in the core fiber that is in a crystalline state. This crystalline state is characterized by a well-ordered and tightly packed molecular arrangement, which contrasts with the less ordered structure of the amorphous regions. The degree of crystallinity impacts crucial properties of the SMP, such as its thermal responsiveness, mechanical strength, flexibility, and the efficacy of its shape-memory effect.

[0092] For the semi-crystalline shape-memory polymers (SSMPs) as disclosed herein, the degree of crystallinity can be quantitatively determined and is typically expressed as a percentage. This percentage reflects the ratio of the crystalline portion to the total volume of the polymer, encompassing both crystalline and amorphous areas. The invention specifically focuses on polymers with a degree of crystallinity between 3% and 70%, more preferably between 3% and 60%, most preferably between 3 and 50%, and may have a degree of crystallinity in the numerical range obtained by combining any two of the following end point values: 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41%, 43%, 45%, 47%, 49%, 51%, 53%, 55%, 57%, 59%, 61%, 63%, 65%, 67%, 69%, or 70%. Such specified ranges of crystallinity are crucial for achieving the desired balance of material properties such as rigidity, flexibility, and phase transition temperature, ensuring optimal shape-memory function and mechanical performance for various applications.

[0093] In this invention, the degree of crystallinity is precisely determined using wide-angle X-ray scattering (WAXS). This technique involves analyzing the diffraction patterns obtained from the polymer to distinguish between the crystalline and amorphous regions. Such precise determination of crystallinity is fundamental for ensuring the covered shape-memory polymeric fibers meet the specific requirements and standards necessary for their intended applications, like in textiles, medical devices, or other technical uses where shape-memory and mechanical properties are critical. Such measurements can be performed using a Bruker D8 Discover X-ray diffraction system with a two-dimensional detector from Bruker AXS (Karlsruhe, Germany) with a suitable X-ray generator that generates, for example, copper K-alpha radiation with a wavelength of 0.154 nm and can be operated with a voltage of 40 kV and a current of 40 mA. The beam can be focused and the geometric properties adjusted using standard means and methods known from the state of the art, e.g. a graphite monochromator and a pinhole collimator with an aperture of 0.8 mm. The samples must be illuminated for a suitable time, e.g. 60 s in transmission geometry, and the diffraction images can be recorded at a distance of 15 cm between the sample and the detector. The measurements can be performed at room temperature and the diffraction images were taken from 8 to 42 of scattering angle. The two-dimensional diffraction images can be integrated to obtain plots of intensity versus diffraction angle. These profiles can be analyzed using suitable software known to the skilled person, e.g. Bruker's TOPAS software, to determine the degree of crystallinity (DOC), which is the ratio of the area of the crystalline peaks to the total area under the diffraction curve (area of the crystalline peaks plus area of the amorphous halo).

[0094] In a preferred embodiment the semi-crystalline shape-memory polymer (SSMP) is selected from the list comprising or consisting of semi-crystalline polyesters, such as polycaprolactone, ethylene-co-monomer-polymers, such as poly[ethylene-co-vinyl acetate] (PEVA), poly(ethylene-1-octene), poly[ethylene-co-ethyl acrylate-co-maleic anhydride] (PEEAMA), poly[ethylene-co-(methyl acrylate)-co-(glycidyl methacrylate)] (PEMAGMA), di-or multi-block-co-polymers, such as amorphous multi block cycloaliphatic polyetherurethane (PEU) consisting of poly(tetramethylene glycol) (PTMEG), 1,4 butanediol (1,4-BD) and methylene bis(p-cyclohexyl isocyanate) (H12MDI), or semi-crystalline ionomers, such as perfluorosulphonic acid ionomer (PFSA). These classes of shape-memory polymers have been shown to be thermally programmable shape-memory polymers with different programming temperatures and chemical properties, although they are known to exhibit degradation effects of the shape-memory properties associated with strains in excess of the maximum engineering strain and are thus often not recoverable over multiple cycles or can be irreversibly damaged during programming. It is therefore an achievement of the inventors to have found that the combination the semi-crystalline shape-memory polymers disclosed herein with a substantially unstretchable yarn results in a covered shape-memory polymeric fiber which is mechanically robust over several thermal programming and recovery cycles.

[0095] Preferably, the semi-crystalline core fiber is selected from shape-memory polymers selected from the group of polycaprolactone, poly[ethylene-co-vinyl acetate] (PEVA), poly(ethylene-1-octene), polycyclooctene containing trans-polyocentamer (PCO/TOR), poly[ethylene-co-ethyl acrylate-co-maleic anhydride] (PEEAMA), poly[ethylene-co-(methyl acrylate)-co-(glycidyl methacrylate)] (PEMAGMA), perfluorosulphonic acid ionomer (PFSA), amorphous multi block cycloaliphatic polyetherurethane (PEU) consisting of poly(tetramethylene glycol) (PTMEG), 1,4 butanediol (1,4-BD) and methylene bis(p-cyclohexyl isocyanate) (H12MDI), most preferably the semi-crystalline core fiber is of a poly[ethylene-co-vinyl acetate] (PEVA) polymer.

[0096] Furthermore, in a preferred embodiment of the covered shape-memory polymeric fiber, the core fiber is selected from shape-memory polymers selected from the group of polycaprolactone, poly[ethylene-co-vinyl acetate] (PEVA), poly(ethylene-1-octene), polycyclooctene containing trans-polyocentamer (PCO/TOR), poly[ethylene-co-ethyl acrylate-co-maleic anhydride] (PEEAMA), poly[ethylene-co-(methyl acrylate)-co-(glycidyl methacrylate)] (PEMAGMA), perfluorosulphonic acid ionomer (PFSA), amorphous multi block cycloaliphatic polyetherurethane (PEU) consisting of poly(tetramethylene glycol) (PTMEG), 1,4 butanediol (1,4-BD) and methylene bis(p-cyclohexyl isocyanate) (H12MDI).

[0097] In an especially preferred embodiment of the covered shape-memory polymeric fiber according to the invention, the shape-memory polymer comprises poly[ethylene-co-vinyl acetate] (PEVA), wherein poly[ethylene-co-vinyl acetate] is formed from a poly[ethylene-co-vinyl acetate] polymer (PEVAP), preferably comprising a cross-linker and/or an initiator, for example by curing which preferably takes place under UV, beta or gamma radiation.

[0098] In a preferred embodiment of the current invention, a shape-memory polymeric fiber may be a cross-linked shape-memory polymeric fiber. This fiber is characterized by its enhanced structural integrity and improved shape-memory properties due to the cross-linking process. The cross-linking within the polymer structure of the fiber is achieved by incorporating a suitable cross-linking agent, as previously defined, which reacts with the polymer chains to create stable cross-links. A cross-linked shape-memory polymeric fiber may preferably be a covalently cross-linked polymeric fiber.

[0099] The cross-linked shape-memory polymeric fiber may exhibit superior mechanical strength and shape recovery compared to its non-cross-linked counterparts. This is a result of the cross-links acting as junction points within the polymer matrix, influencing the reordering process, and crystallinity of the bulk material. The cross-linking grade is carefully controlled to balance flexibility and rigidity, ensuring that the fiber can be deformed to a temporary shape and then recover its original shape upon exposure to a specific stimulus, typically a change in temperature.

[0100] Poly [ethylene-co-vinyl acetate] (PEVA), also referred to as covalently cross-linked Poly [ethylene-co-vinyl acetate] (cPEVA), in the spirit of the current invention refers to a co-polymer from vinyl acetate and ethene, which is cross-linked by chemical means to form new covalent bonds starting from poly[ethylene-co-vinyl acetate] polymer (PEVAP). The cross-linking can be induced by a cross-linker or cross-linking agent. Advantageously, in some embodiments PEVA may be prepared by blending different poly[ethylene-co-vinyl acetate] polymers, for example PEVAPs with a different vinyl acetate content, and cross-linked by adding cross-linking agents and/or initiators and/or by curing.

[0101] In another preferred embodiment of the covered shape-memory polymeric fiber according to the current invention, the vinyl acetate content in the poly[ethylene-co-vinyl acetate] polymer is between 5% and 50% of the total weight of the polymer. In a preferred embodiment of the invention, the vinyl acetate content in poly[ethylene-co-vinyl acetate] is between 3 wt % and 45 wt % of the total weight, alternatively preferably may have a degree of crystallinity in the numerical range obtained by combining any two of the following end point values: 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41%, 43%, or 45%. This is because the VA content significantly influences the properties of the PEVA, such as its flexibility, thermal behavior, and shape-memory characteristics. An increase in VA content is associated with a decrease in degree of crystallinity.

[0102] The vinyl acetate content (VA-content) of PEVA and PEVAP in the context of this invention can be preferably determined with derivative thermogravimetric (DTG) analysis. Two decomposition stages of PEVA and PEVAP can be observed, which are associated with the formation of volatile products. The first peak of the DTG curves occurs in the temperature range from 300 C. to 410 C., which can be attributed to the deacetylation of VA segments, while at higher temperatures around 420 C. to 510 C. the second peak for the decomposition of the residues occurs, which is caused by the breaking of the CC bond along the main chains. Thus, the composition of cPEVA could be determined based on the weight loss of the acetic acid groups, according to:

[00019]$\mathrm{VA}-\mathrm{content}\mathrm{wt}\%=\frac{w_1\left(\frac{M_w^{\mathrm{VA}}}{M_w^{\mathrm{acetate}}}\right)}{w}100\%,$

wherein w.sub.1 is the weight loss due to the deacetylation of the VA segments in the temperature range from 300 C. to 410 C. and w is the total weight of the PEVAP and PEVA samples. M.sub.w is the molar mass of vinyl acetate (VA) and acetic acid (acetate) groups.

[0103] In a preferred embodiment of the covered shape-memory polymeric fiber according to the invention, the poly[ethylene-co-vinyl acetate] polymer (PEVAP) comprises a cross-linker and/or an initiator. Comprising in this context is preferably realized by blending one, preferably at least two, poly[ethylene-co-vinyl acetate] polymer(s) with different vinyl acetate contents, with a cross-linker, preferably TAIC and an initator, preferably BP, before the cross-linking initiated with irradiation (curing), yielding PEVA, preferably covalently cross-linked PEVA.

[0104] An exemplary method for conducting DSC measurements, as applied in this invention, is outlined as follows: DSC measurements were carried out using a DSC 204 Phoenix (NETZSCH, Selb, Germany). This involved a comprehensive heating-cooling-heating cycle to accurately characterize the thermal properties of PEVAP and PEVA shape-memory polymers according to the current invention. The procedure began with the first heating process, which ramped up from ambient temperature to 200 C. at a heating rate of 20 C. per minute. This step was crucial for determining the material's behavior upon heating. After reaching 200 C., the sample underwent a cooling phase down to 100 C. This cooling was conducted at varied rates, including 100 C./min, 50 C./min, 20 C./min, 10 C./min, 5 C./min, and 1 C./min. These varying rates were employed to precisely determine the temperature at which crystallization of the material occurred, an essential factor for understanding the material's thermal behavior and stability.

[0105] Following the cooling phase, a second heating run was performed. This stage involved heating the sample from 100 C. back up to 200 C. During this second heating, critical thermal transition temperatures of the PEVAP and PEVA shape-memory polymers, specifically the melting temperature and the glass transition temperature, were accurately measured.

[0106] Additionally, the crystallinity index (xc) of the PE segments in PEVAP and PEVA shape-memory polymers can be calculated from the exothermic curves obtained during the DSC analysis. The crystallinity index is a crucial parameter indicating the degree of crystallinity within the polymer structure, which impacts the material's mechanical and thermal properties. The calculation is based on the following Equation:

[00020]$c=\frac{H_m}{H_{100}}$

[0107] Here, H.sub.m represents the integrated melting enthalpy, corresponding to the area under the melting peak in the DSC curve. H.sub.100 is the specific melting enthalpy for a 100% crystalline PE segment, which in this example is 287.3 J/g. This calculation allows for determination of the crystalline structure within PEVAP and PEVA shape-memory polymers. This DSC method provides a comprehensive thermal analysis, ensuring that the shape-memory polymers used in the invention meet the required specifications for optimal performance in covered shape-memory polymeric fiber (cSMPF) of the invention and/or shape-memory textile and/or shape-memory fabric comprising the same. Experimental results from some exemplary covalently cross-linked poly[ethylene-co-vinyl acetate] (PEVA) and poly[ethylene-co-vinyl acetate] polymer (PEVAP) with different vinyl acetate contents are shown in table 1.

TABLE-US-00001 TABLE 1 Composition and degree of crystallinity (DOC) and crystallinity index (c) of some embodiments of covalently cross-linked poly[ethylene-co-vinyl acetate] (PEVA) and poly[ethylene- co-vinyl acetate] polymer (PEVAP) with different vinyl acetate contents VA-Content G DOC c No Polymer [wt %] [%] [%] [%] 1 PEVAP 11 45.7 0.7 33.7% 2 PEVAP 20 36.7 0.8 24.8% 3 PEVAP 31 27.6 0.1 14.3% 4 PEVAP 35 13.1 0.7 6.0% 5 PEVAP 44 8.4 0.8 3.7% 6 PEVA 11 95 1 35.9 0.1 30.0% 7 PEVA 20 96 1 27.6 0.2 21.3% 8 PEVA 31 96 1 15.2 0.1 16.4% 9 PEVA 35 94 1 7.8 0.3 11.3% 10 PEVA 44 95 1 5.6 0.4 5.2%

[0108] In some preferred embodiments of the covered shape-memory polymeric fiber according to the current invention, the amount of cross-linking agent and initiator in the poly[ethylene-co-vinyl acetate] polymer ranges from 0.5% to 5.0% by weight.

[0109] In some other preferred embodiments of the covered shape-memory polymeric fiber according to the current invention the cross-linker is triallyl isocyanorate (TAIC).

[0110] In some further preferred embodiments of the covered shape-memory polymeric fiber according to the current invention, the amount of cross-linking agent and initiator in the poly[ethylene-co-vinyl acetate] polymer ranges from 1.0% to 2.0% by weight.

[0111] In a preferred embodiment of the covered shape-memory polymeric fiber according to the invention, the cross-linking agent is benzophenone (BP).

[0112] In an embodiment of the invention, the polymers are optionally present as a blend, wherein the content of each polymer in the blend is at least 10 wt %.

[0113] In some preferred embodiments, the content of each shape-memory polymer in the blend may be in the numerical range obtained by combining any two of the following end point values: 1 wt %, 3 wt %, 5 wt %, 7 wt %, 9 wt %, 11 wt %, 13 wt %, 15 wt %, 17 wt %, 19 wt %, 21 wt %, 23 wt %, 25 wt %, 27 wt %, 29 wt %, 31 wt %, 33 wt %, 35 wt %, 37 wt %, 39 wt %, 41 wt %, 43 wt %, 45 wt %, 47 wt %, 49 wt %, 51 wt %, 53 wt %, 55 wt %, 57 wt %, 59 wt %, 61 wt %, 63 wt %, 65 wt %, 67 wt %, 69 wt %, 71 wt %, 73 wt %, 75 wt %, 77 wt %, 79 wt %, 81 wt %, 83 wt %, 85 wt %, 87 wt %, 89 wt %, 91 wt %, 93 wt %, 95 wt %, 97 wt %, or 99 wt %, wherein the content of all polymer contents in the blend add up to 100 wt %.

[0114] In another embodiment, the hard segment content such as (H12MDI)/(1,4-BD), polyethylene co-monomer content, trans-double-bond content may preferably vary between 40% and 95% in the polymers. In some preferred embodiments, the hard segment content trans-1,4 butadiene monomer block content in 1,4 butanediol (1,4-BD) and methylene bis(p-cyclohexyl isocyanate) (H12MDI) may preferably vary between 1 and 50 mol % in the polymers.

[0115] The vinyl acetate in the poly[ethylene-co-vinyl acetate] polymer may preferably vary between 5% and 50% of the total weight of the polymer. In an embodiment of the invention, the poly[ethylene-co-vinyl acetate] polymer (PEVAP) comprises a cross-linker such as triallyl isocyanorate (TAIC) and/or an initiator such as benzophenone (BP). Preferably, the amount of cross-linking agent and initiator in the poly[ethylene-co-vinyl acetate] polymer ranges from 0.5% to 5.0% by weight, such as from 1.0% to 2.0% by weight.

[0116] In this disclosure, the terms cross-linker, crosslinker, and cross-linking agent are synonymous and describe chemical compounds employed to establish cross-links within a polymer matrix. These agents are characterized by having at least two reactive functional groups, essential for forming cross-links, such as covalent bonds, between separate polymer chains and/or between different segments of the same polymer chain. In an alternative mechanism, certain cross-linkers act by creating reactive sites directly on the polymer chains. These sites subsequently react with each other, facilitating cross-linking. This type of cross-linking typically involves the use of strong acids or peroxides.

[0117] The proportion of the cross-linker relative to the total weight of the polymer is a critical factor, as it significantly influences the cross-linking grade. It is preferable that the proportion of the cross-linker, relative to the total weight of the shape-memory polymer or its precursor prior to the initiation of the cross-linking process, falls within the range of 0.05 wt % to 5 wt %. More specifically, an optimal range for enhanced efficacy and balance in the properties of the resulting polymer is between 0.1 wt % and 2.5 wt %. This proportion is critical in influencing the final properties of the shape-memory polymer, particularly in terms of its cross-linking density, mechanical strength, and thermal responsiveness.

[0118] In the context of shape-memory polymers the level of cross-linking, also referred to as cross-linking grade holds particular significance. A higher cross-linking grade typically correlates with reduced crystallinity, in particular reduced degree of crystallinity, within the polymer. This relationship is of paramount importance in the design of shape-memory polymers. The crystallinity level directly affects the transition temperatures of these semi-crystalline polymers, which is a crucial aspect in tailoring their thermal-responsive behavior to meet the specific requirements of the current invention. Therefore, the selection and concentration of cross-linkers must be carefully considered to achieve the desired balance between cross-linking grade and crystallinity, ensuring the optimal performance of the shape-memory polymers in their intended applications.

[0119] In the context of ethylene-co-monomer-polymers or di-or multi-block-co-polymers comprising at least one polyethylene and/or polyalkene polymer block, cross-linkers are preferably substances with at least two, more preferably between 2 and 4 alkene functional groups, preferably allyl or vinyl groups. These cross-linkers can react with radicals generated on a polymer, preferably a shape-memory polymer within the meaning of the present invention, by irradiation and/or an initiator, preferably a photoinitiator, such as benzophenone (BP). This has the advantage that no functional groups are required for this cross-linking, although some functional groups can be cross-linked radically, such as acetate groups, and that the cross-linking grade can be influenced by the irradiation time and/or the dose and/or the concentration of the initiator and/or the cross-linker, resulting in a variety of different parameters suitable for a wide range of potential shape-memory polymer.

[0120] The gel content in a polymer and its cross-linking grade are closely related concepts in polymer chemistry. In a specific embodiment of the present invention, a shape-memory polymer, which is preferably a cross-linked shape-memory polymer and most preferably a covalently cross-linked shape-memory polymer, is characterized by a gel content ranging from 60 to 100%, with a more preferred range being between 70 and 100%. This embodiment is particularly significant for ensuring the desired physical and mechanical properties of the shape-memory polymers used in various applications. In some preferred embodiments, the gel content a shape-memory polymer may be in the numerical range obtained by combining any two of the following end point values: 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 98%, 99%, and 100%.

[0121] The polymers constituting the core fibers, or their blends, in this embodiment, can undergo cross-linking through different mechanisms, including covalent bonds, ionic interactions, or crystallite formation. However, the emphasis in this embodiment is on covalently cross-linked polymer networks, which are known for their robustness and stability. According to standards such as ASTM D2765 or ISO 10147, these covalently cross-linked polymers exhibit a gel content ranging from 60 to 100%.

[0122] To determine the gel content (G) of the cross-linked core fibers, specifically the cross-linked shape-memory polymers within these fibers, a solvent extraction method is employed. This involves immersing the polymer sample in solvents like toluene or xylene at a constant temperature of 110 C. or lower. The extraction process lasts for 24 hours, followed by an additional 24 hours of solvent evaporation in a vacuum oven set at 45 C. The gel content is then calculated using the following equation:

[00021]$G=\frac{m_d}{m_{\mathrm{iso}}}*100\%$

[0123] Here, m.sub.d represents the dry weight of the sample after extraction, and miso is the isolated weight of the sample before extraction.

[0124] It's important to note that for the purposes of this embodiment, the fibers that are not subjected to extraction are used for covering and for conducting various investigations, such as thermo-mechanical analysis and evaluation of shape-memory properties.

[0125] This embodiment underscores the relationship between gel content and the cross-linking grade in polymer chemistry. A higher gel content indicates a more extensive cross-linked network, which is crucial for achieving the desired shape-memory characteristics. The specific range of gel content mentioned ensures that the polymers maintain an optimal balance between flexibility and structural integrity, making them ideal for applications requiring precise and reliable shape-memory functionality.

[0126] In some preferred embodiments of the covered shape-memory polymeric fibers (cSMPF), the elastic modulus (E), also referred to as Young's modulus, preferably determined at 25 C., is between 1.00.5 and 15.00.5 MPa, preferably between 2.00.5 and 10.00.5 MPa. This allows for a broad range of applications were different stress and strains are required.

Method of Production

[0127] The current invention furthermore is related to a method for producing the covered shape-memory polymeric fiber as disclosed herein including the steps of extruding a core fiber of a poly[ethylene-co-vinyl acetate] polymer, optionally together with a cross-linker or cross-linking agent, optionally curing the extruded fibers for covalent cross-linking and winding a covering yarn around the core fiber.

[0128] In a preferred embodiment of the method of the invention the curing takes place under UV, beta or gamma radiation.

[0129] In another aspect, the present invention relates to a method for manufacturing the covered shape-memory polymeric fiber (cSMPF). The method includes the steps of extruding a core fiber of a poly[ethylene-co-vinyl acetate] polymer, optionally together with a cross-linker or cross-linking agent, optionally curing the extruded fibers for covalent crosslinking, preferably by applying radiation such as UV, beta or gamma radiation, and winding a covering yarn around the core fiber. Alternatively cross-linking can be performed by heating to temperatures below melting temperature of specific polymer defined by ISO 11357, while stretching of the core fibers after extrusion can be performed up to 10 times comparing to unstretched extruded fiber. This is preferably done by pulling the fibers through a cooling bath and winding them around a bobbin with a defined tension or force.

[0130] The invention furthermore relates to a method for producing the covered shape-memory polymeric fiber (cSMPF) as claimed in any one of the previous claims including the steps of [0131] a) extruding a core fiber (10), of a core fiber precursor for a shape-memory polymer according to the invention, preferably with a cross-linker or cross-linking agent, more preferably of a poly[ethylene-co-vinyl acetate] polymer, optionally together with a cross-linker or cross-linking agent, then [0132] b) curing the extruded fiber, preferably under UV, beta or gamma radiation for covalent cross-linking, then [0133] c) winding a covering yarn (20) around the core fiber (10).

[0134] Curing in the context of the present invention refers to the process of inducing cross-linking within the shape-memory polymer, typically aiming for covalent cross-linking. This step stabilizes the polymer structure, significantly influencing its mechanical, thermal, and most importantly shape-memory properties. For polymers containing ethylene or olefin monomers, as in this case, the curing can involve direct radical cross-linking. This is often achieved using peroxides and/or photoinitiators, such as benzophenone, as initiators, and preferably a cross-linker, such as TAIC. The initiators decompose under specific conditions, such as thermic activation or irradiation with electromagnetic radiation, to generate free radicals, which facilitate the formation of covalent bonds between polymer chains.

[0135] This initial step involves the extrusion of a core fiber precursor, which is formulated to become a shape-memory polymer. In some preferred embodiments, the precursor is poly[ethylene-co-vinyl acetate] polymer (PEVAP). Optionally, a cross-linker or cross-linking agent is included in the mixture. The presence of a cross-linker is crucial when enhanced structural integrity or specific mechanical properties, including shape-memory properties, are desired in the final cSMPF.

[0136] Alternatively, curing can be carried out using irradiation methods, such as UV, beta, or gamma radiation in combination with an initiator, and optionally a cross-linker. These methods involve exposing the extruded polymer to high-energy radiation, which generates free radicals and initiates the cross-linking process. Irradiation provides a controlled way to achieve cross-linking, allowing for precise manipulation of the polymer's properties.

[0137] After curing, a covering yarn is wound around the core fiber. This yarn is typically substantially unstretchable, providing additional structural support and protection to the core fiber.

[0138] In a preferred embodiment of the invention, the shape-memory polymer precursor is provided before step a), which is prepared through a comprehensive compounding process. This process involves several carefully controlled steps to ensure the optimal blending of the polymer(s) and reagents, preferably initiator and cross-linker.

[0139] In some preferred embodiments, a 50:50 mixture of initiator and cross-linker, preferably BP and TAIC is prepared. Then, this mixture is manually blended with the shape-memory polymer precursor, for example PEVAP (poly[ethylene-co-vinyl acetate]) polymer granulates. This manual mixing ensures a preliminary and uniform distribution.

[0140] The manually mixed materials are then compounded in a twin-screw extruder. The extruder is set to a specific temperature profile: 25 C. in the feeding zone, gradually increasing to 80 C., and then maintaining 110 C. across the melting and mixing zones, before finally reaching 100 C. at the die. The screw rotation speed is preferably between 30-60 rpm, more preferably between 45 and 55 rpm. This controlled environment ensures thorough mixing and melting of the components, leading to a homogenous blend.

[0141] Following the first extrusion, the continuous filament may be cut into granulates. This palletizing step transforms the extruded blend into manageable granules, facilitating further processing and handling. Furthermore, this blend may be advantageously stored under controlled conditions for further processing.

[0142] In some preferred embodiments, the shape memory polymer precursor may be pelletized and extruded multiple times to achieve a more uniform distribution.

[0143] Preferably, the granulates are dried overnight at a temperature of 30 to 80 C., preferably 35 to 55 C. This drying step is crucial to remove any residual moisture, which could potentially interfere with the subsequent curing process of the polymer.

[0144] In a preferred embodiment, the shape-memory polymeric fibers before curing are provided as monofilaments with diameters ranging from 0.05 mm to 0.5 mm. This diameter range is chosen to provide a balance between the mechanical strength of the fibers and their flexibility. Preferably, the mixture is fed into a single screw extruder for extrusion. The extruder is equipped with filament dies of various diameters to produce monofilaments with the desired thickness as disclosed herein. In some embodiments of the extrusion process, the feeding zone may be maintained at 20 C. to prevent premature melting of the mixture. The temperature may then increased to 80 C., followed by a consistent temperature of 110 C. across the melting zones. Finally, the temperature at the die is set to 100 C. This controlled temperature profile is crucial for achieving uniform melting and smooth flow of the polymer through the dies. The screw rotation speed during extrusion is kept between 5 and 20 rpm. This range of rotation speeds allows for careful control over the extrusion process, ensuring that the monofilaments are extruded at a consistent rate and with uniform diameter.

[0145] In another preferred embodiment, the shape-memory polymeric fibers before curing are provided as multifilament with a linear density of 40 to 500 dtex. This may be achieved through melt-spinning, which involves an extrusion-like setup but is distinct in its use of a spinneret at the end. The spinneret contains multiple holes, preferably between 20 to 200, more preferably between 36 to 150 through which multiple filaments are extruded. Preferably, the filaments are extruded simultaneously and collected as one continuous filament. This process allows for the production of a bundle of filaments, which can then be used in various textile applications.

[0146] In some preferred embodiments, the shape memory polymer fibers have been cured by in-line UV irradiation, which is integrated into the fiber extrusion process. This method allows for immediate cross-linking of the fibers during their manufacture, streamlining the manufacturing process. Alternatively, cross-linking can also be carried out as a post-processing step. This can be done by UV irradiation or electron beam irradiation.

[0147] Irradiation with electron beams can advantageously be carried out with different doses, preferably between 50 and 200 kGy, particularly preferably between 90 and 170 kGy, whereby different degrees of crosslinking can be achieved depending on the specific requirements of the application. This type of irradiation is particularly effective in achieving a high cross-linking grade by inducing free radicals in the polymer, which is advantageous for applications requiring robust shape memory properties.

Shape-Memory Textile and Fabric

[0148] In a further embodiment, the invention relates to a shape-memory fabric, comprising or consisting of a covered shape-memory polymeric fiber (cSMPF) comprising a core fiber (10), and a substantially unstretchable covering yarn (20) according to the invention, wherein the covered shape-memory polymeric fiber (cSMPF) is arranged in [0149] a) a shape-memory mesh network of interwoven or intertwined, preferably by techniques such as knitting, weaving, crotcheting, brainding, cSMPFs, forming an operatively connected structure, and/or [0150] b) a shape-memory inlay, arranged in a second fabric, preferably non-shape-memory fabric,
wherein the maximum engineering strain of the core fiber (10), is reduced to at most the strain at the yield point of the uncovered core fiber (10). This has the advantage that the robust shape-memory effect of a cSMPF, as disclosed herein, is coordinated with the surrounding fibers so that the entire textile uniformly exhibits the desired shape-memory properties.

[0151] A non-shape-memory fabric is any fabric that doesn't comprise or consist of a covered shape-memory polymeric fiber (cSMPF) according to the invention. Common fabrics are known to the person skilled in the art. Preferably, a further and/or a second fabric is a non-shape-memory fabric. This enables the integration of well-defined fabrics known from the prior art, which can be supplemented with the shape-memory effect of the cSMPFs according to the invention.

[0152] The term interwoven in the spirit of the invention refers to the method of arranging covered shape-memory polymeric fibers (cSMPFs) by systematically crossing them over and under each other. This weaving process, for example as defined by ISO 3572:1976, creates a fabric or mesh network where the cSMPFs intersect at regular intervals, forming a grid-like structure. In an interwoven design, the cSMPFs can be aligned in perpendicular or other angular arrangements to create various weave patterns. The interweaving of cSMPFs ensures a uniform distribution of the shape-memory effect throughout the fabric, allowing for consistent performance and functionality.

[0153] Intertwining, on the other hand, involves twisting or entangling cSMPFs together without following the systematic over-and-under pattern of weaving. This method results in a more flexible and potentially less structured arrangement of fibers. Intertwined cSMPFs create a fabric where the fibers are looped or knotted around each other, forming a network that retains the shape-memory properties while allowing for more flexibility and adaptability in the textile's design.

[0154] In both interwoven and intertwined arrangements, the cSMPFs form an operatively connected structure. This structure is akin to a mesh network or fabric, where each individual fiber contributes to the overall shape-memory functionality of the textile. The operative connection means that the movement or deformation of one fiber affects and is coordinated with the surrounding fibers, enabling the entire textile to exhibit the desired shape-memory properties uniformly.

[0155] A person skilled in the art of textile manufacturing would understand various methods of arranging fibers to create these operatively connected structures. Techniques such as knitting, weaving, braiding, and knotting can be employed to form shape-memory fabrics. The choice of technique depends on the desired properties of the final product, such as flexibility, stretchability, strength, and the specific shape-memory characteristics required.

[0156] Additionally, the invention encompasses the concept of a shape-memory inlay. This involves embedding or integrating the cSMPF within a second fabric, preferably a non-shape-memory fabric. The inlay technique allows for the incorporation of shape-memory properties into conventional fabrics, enhancing their functionality without altering their fundamental characteristics. This integration can be achieved in a specific knitting process as well as through sewing, adhesive bonding, or other methods known to those skilled in the art.

[0157] Furthermore, the present invention relates to a shape-memory textile comprising a covered shape-memory polymeric fiber (cSMPF) according to the current invention and at least a further fabric, preferably non-shape-memory fabric, and/or a further fiber, preferably non-shape-memory fiber, wherein the cSMPF is arranged in and/or on the shape-memory textile by knitting, preferably circular knitting or flat knitting or jacquard knitting, weaving, preferably inlay weaving or layered weaving, braiding, embroidery, composite techniques or as 3D textile structure, wherein the maximum engineering strain of the core fiber (10), is reduced to at most the strain at the yield point of the uncovered core fiber (10). This specification ensures that the structural integrity and the shape-memory properties of the cSMPF are maintained within the textile, preventing overstretching and potential damage to the fibers.

[0158] In the present invention, knitting is utilized as a preferred method for integrating covered shape-memory polymeric fibers (cSMPF) into shape-memory textiles. This technique involves interlocking loops of yarn to create a fabric, which can be executed in various forms. Circular knitting is the preferred method for producing seamless, tubular structures, whereby the knitting is done in a continuous circular motion. This technique is ideal for the production of items such as socks, tubulars and other circular garments. The integration of cSMPFs into circular knitting can lead to innovative applications such as tubular compression garments with shape-memory properties. Flat knitting involves knitting back and forth in rows, allowing for more intricate designs and patterns. Flat knitting is suitable for the production of larger, flat pieces of fabric that can be cut and sewed into specific garments. The use of cSMPFs in flat knitting can result in shape-memory fabrics with complex geometries and detailed designs. As a specialized form of knitting, Jacquard knitting allows for the creation of multi-colored and complex patterns. The use of cSMPFs in Jacquard knitting not only adds functional shape-memory characteristics but also enhances the aesthetic appeal of the fabric, making it suitable for fashion and design-oriented applications.

[0159] Embroidery, as applied in this invention, involves the decorative stitching of covered shape-memory polymeric fibers (cSMPFs) onto a base fabric. This technique allows for precise placement of cSMPFs, enabling the addition of shape-memory functionalities in specific patterns or designs. Embroidery can be used to create localized regions of shape-memory properties, which can add functional value, such as adaptive fit or dynamic structural support in specific areas of the textile, for example in sport and leisure garments as well as specialised medical applications, for example individual burn and scar dressing.

[0160] Composite techniques refer to the combination of cSMPFs with other materials to form a composite textile. This approach can involve layering, bonding, or embedding cSMPFs with other fabrics or materials to enhance the overall properties of the textile. The result is a synergistic combination where the shape-memory properties of the cSMPFs are integrated with the structural, thermal, or other characteristics of different materials. Composite techniques are particularly useful in applications requiring a balance of flexibility, strength, and adaptive shape-memory functions.

[0161] Braiding involves intertwining multiple strands of cSMPFs, and possibly other types of fibers, in a systematic pattern. This method provides a unique way to create strong, flexible, and durable textiles with shape-memory properties. Braided structures are particularly suited for applications requiring high tensile strength and resilience, such as in medical devices, protective clothing, or in structural applications where the shape-memory effect can be utilized for dynamic functionality. The braiding process allows for the creation of complex, three-dimensional textile structures with enhanced shape-memory characteristics.

[0162] Additionally, the present invention relates to a method for preparing a shape-memory textile and/or a shape-memory fabric, comprising the steps of [0163] a) Providing covered shape-memory polymeric fiber (cSMPF), then [0164] b) Arranging the covered shape-memory polymeric fiber (cSMPF) into and/or onto a textile or fabric, preferably by knitting, particularly preferably circular knitting or flat knitting or jacquard knitting, weaving, particularly preferably inlay weaving or layered weaving, braiding, embroidery, composite techniques, or 3D textile structuring.

[0165] In summary, this method of preparing a shape-memory textile or fabric is characterized by its versatility and adaptability. By selecting and combining different techniques for arranging the cSMPF, a wide range of textiles and fabrics with customized shape-memory properties can be created. This approach allows for the development of innovative products suitable for various applications, from clothing and accessories to medical devices and industrial materials.

[0166] The first step in the supply process involves the production or sourcing of cSMPFs, which are the basic building blocks of shape-memory textiles or fabrics. These fibers are characterized by a core of shape memory polymer, which is then covered with a non-stretchable yarn. The composition, thickness and properties of these fibers are selected based on the desired properties of the final textile or fabric.

Use of the Covered Shape-Memory Polymeric Fiber

[0167] Furthermore, the use of the covered shape-memory polymeric fiber as described herein for compression garments, orthopedic bandages, orthoses, posture correction garments, push-up garments, corsets and corsages, and sports garments is disclosed.

[0168] In another aspect, the present invention relates to a use of the covered shape-memory polymeric fiber (cSMPF). The cSMPF can be used for example for compression garments, orthopedic bandages, orthoses, posture correction garments, push-up garments, corsets and corsages, and sports garments.

[0169] One embodiment of the current invention relates to the field of textiles, in particular shape-memory polymeric fibers (SMPF) for textile applications or medical applications where shape fixity and recovery can be kept constant over multiple shape-memory cycles. The present invention provides a covered shape-memory polymeric fiber (cSMPF) having a core fiber of semi-crystalline polymer fibers and a substantially unstretchable covering yarn wound around the core fiber in a manner that the maximum engineering strain (.sub.max) of the core shape-memory fiber is reduced to at most the strain at the yield point (.sub.yield) of the uncovered core fiber. Thus, the covering yarn is used to limit the stretchability or deformation of the core shape-memory fibers during programming so as to ensure maximum recoverable strain.

TABLE-US-00002 TABLE 2 Compression classes of medical garments according to RAL-GZ 387/1 (Gtesicherung Medizinische Kompressionsstrmpfe - Quality assurance for medical compression stockings) Compression class Compression intensity Compression in kPa I light 2.4 to 2.8 II medium 3.1 to 4.3 III strong 4.5 to 6.1 IV very strong 6.5 and above

[0170] Also disclosed by the current invention is a use of the covered shape-memory polymeric fiber in a textile, preferably a shape-memory textile, such as a technical, medical, orthopedic, industrial, sports or leisure textile.

[0171] Preferred is a use of the covered shape-memory polymeric fiber in a fabric, preferably a shape-memory fabric, such as a technical, medical, orthopedic, industrial, sports or leisure fabric.

[0172] Particularly preferred is a use of the shape-memory textile according or a shape-memory fabric according as a medical, orthopedic and/or compression garment, preferably repeatedly thermally programmable by heating between 4 and 70 C. on a subject's body. This increases comfort and effectiveness without risking burns to the subject's body.

[0173] Also preferred is a use of the shape-memory textile according or a shape-memory fabric according as a sport or leisure garment, preferably repeatedly thermally programmable by heating between 4 and 70 C. on a subject's body.

[0174] In a preferred embodiment the shape-memory textile and/or shape-memory fabric is specifically tailored for individuals within the age range of 50 to 90 years. This embodiment is designed to address age-related conditions such as poor circulation, edema, varicose veins, and support during post-surgical recovery. The garment features graduated compression to enhance blood flow, normalize blood backflow, reduce swelling, and improve overall comfort, making it especially suitable for daily wear and enhancing mobility in this age group.

[0175] Another embodiment is focused on athletes and sports enthusiasts aged between 15 and 50 years. This version of the shape-memory textile and/or shape-memory fabric is engineered to support muscle recovery, reduce fatigue, and enhance athletic performance. It incorporates materials and designs suitable for high-intensity activities and endurance sports. The garment is optimized for activities such as running, cycling, and team sports, where muscle exertion and the need for support are significant.

[0176] Another embodiment of shape-memory textile and/or shape-memory fabric is applications of compression therapy where highly individualized garments and/or bandages are required for each individual case. In this applications, deformation of the patient's body or prescribed therapy demand individual fit and/or compression profile, for example in treatment of burns, scars, or ulcers.

[0177] A dedicated embodiment of the shape-memory textile and/or shape-memory fabric is designed for pregnant women. This garment is tailored to accommodate the changing body during pregnancy, providing support and comfort while managing symptoms like leg swelling. The design ensures safety and ease of use, making it a practical solution for everyday wear during pregnancy.

[0178] One embodiment of the current invention is specifically crafted for individuals suffering from lymphatic disorders such as lymphedema. The shape-memory textile and/or shape-memory fabric is designed to promote lymphatic fluid circulation, helping to reduce swelling and discomfort associated with lymphatic accumulation. Its unique construction is aimed at providing targeted support in affected areas. The shape-memory effect and the thermally programmable nature allow a customizable solution for the subject.

[0179] A further embodiment addresses the needs of individuals, whose condition limits their mobility and/or who faces particular difficulties with pulling compression garments on and off. The shape-memory textile and/or shape-memory fabric can simplify this with a procedure based on shape-memory effect that allows for easier pulling the compression garments on with subsequent adjustment to required fit and compression as well as easier pulling compression garments off without significant irreversible damaging of their therapeutic properties.

[0180] A preferred embodiment addresses the needs of individuals with postural issues or those leading a sedentary lifestyle. The shape-memory textile and/or shape-memory fabric provides postural support, particularly for those who spend extended periods sitting or have occupation-related postural challenges. Its design focuses on promoting correct posture and reducing strain on the back and legs.

[0181] A specialized embodiment is developed for long-distance travelers, particularly those undertaking extended flights. This embodiment of the shape-memory textile and/or shape-memory fabric is designed to prevent circulation-related issues such as deep vein thrombosis (DVT). It features compression properties that promote blood flow in the lower extremities, making it an essential travel accessory for health-conscious travelers.

[0182] Finally, an embodiment is designed for individuals in occupations requiring prolonged standing or heavy physical labor. This embodiment of the shape-memory textile and/or shape-memory fabric helps to reduce leg fatigue, support muscle endurance, and improve overall comfort during long hours of work. It is particularly beneficial for workers in sectors like healthcare, construction, and retail, where physical demand is a constant feature of the job.

[0183] The invention also relates to a thermally programmable textile, such as a technical, medical, orthopedic, industrial, sports or leisure thermally programmable textile, comprising or consisting of the covered shape-memory polymeric fiber or the shape-memory fabric according to the current invention or the shape-memory textile, preferably with a compression force between 0.5 and 8.5 kPa. These levels of compression are critical in medical applications for improving blood circulation, reducing swelling, and offering support to injured or weakened body parts. A further advantageous feature of these garments is their thermally programmable nature, with a range of 40 to 70 C., allowing for the compression level to be easily adjusted on the subject's body, adapting to different recovery stages or swelling levels.

[0184] Herein, the invention discloses a preferred use of the thermally programmable textile as a medical or orthopedic garment, preferably with a compression force between 0.5 and 8.5 kPa, preferably repeatedly thermally programmable by heating between 4 and 70 C. on a subject's body.

[0185] Furthermore, the invention discloses a use of the thermally programmable textile as a sport or leisure garment, preferably with a compression force between 0.5 and 8.5 kPa, preferably repeatedly thermally programmable by heating between 4 and 70 C. on a subject's body.

[0186] Additionally, the invention relates to a thermally programmable fabric, such as a technical, medical, orthopedic, industrial, sports or leisure shape-memory fabric, comprising or consisting of the covered shape-memory polymeric fiber or the shape-memory fabric or the shape-memory textile, preferably with a compression force between 0.5 and 8.5 kPa.

[0187] Herein, the invention discloses a preferred use of the thermally programmable fabric as a medical or orthopedic garment, preferably with a compression force between 0.5 and 8.5 kPa, preferably repeatedly thermally programmable by heating between 4 and 70 C. on a subject's body.

[0188] Furthermore, the invention discloses a preferred use of a thermally programmable fabric as a sport or leisure garment, preferably with a compression force between 0.5 and 8.5 kPa, preferably repeatedly thermally programmable by heating between 4 and 70 C. on a subject's body.

Definitions

[0189] Certain terms and derivations thereof are used in the following description for convenience only and are not intended to be limiting. For example, words such as up, above, upward, down, below, downward, left and right refer to directions in the drawings to which reference is made, unless otherwise indicated. Similarly, words such as inward and outward refer to directions directed toward or away from the geometric center of a device or area or specific parts thereof. References in the singular include the plural and vice versa, unless otherwise indicated.

[0190] In the context of this patent application, the term subject refers to individuals or groups who may benefit from the use of covered shape-memory polymeric fiber (cSMPF) and/or a shape-memory textile and/or shape-memory fabrics comprising the same as disclosed herein.

[0191] Programming, in particular thermally-programming or thermal programming, refers to the process of reversibly changing the shape of a covered shape-memory polymeric fiber comprising a core fiber comprising or consisting of a shape-memory polymer. The shape and properties of a shape-memory polymer can be changed by rearranging the crystalline rigid segments and the switching segments and then equilibrating them. A thermally programmable shape-memory polymer can be programmed by a specific thermic programming process.

[0192] Finally, it should be noted that all features mentioned in the application documents and in particular in the dependent claims, despite the formal reference made to one or more specific claims, should also be granted independent protection individually or in any combination. Further advantages, features and possible applications of the present invention are also apparent from the following description of embodiments and the drawings. All the features described and/or illustrated form the object of the present invention, either individually or in any combination, even independently of their summary in the claims or their references. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination.

[0193] In addition, it should be noted that the skilled person will undoubtedly recognize that the individual features described in the specific embodiments above can be combined with each other in an appropriate manner, provided that there is no contradiction, whereby a separate description of various possible combinations is dispensed with in order to avoid unnecessary repetition.

EXAMPLES

[0194] The present invention is explained in more detail with reference to the following figures and embodiments, without limiting the invention to these. In particular, features shown in the individual figures and described for the respective example are not limited to the respective individual example.

[0195] Examples of embodiments are shown to explain the basic principle of the device according to the invention. It should be noted that the ratio, the dimensions, the extent of deformation or the amount of displacement of the components according to the invention do not correspond to reality for the sake of illustration.

[0196] The singular includes the plural, unless the context clearly indicates otherwise. The features, characteristics and advantages of the present invention described above and the manner in which they are achieved will be more clearly understood in the context of the following description of the embodiments. Where the term may is used in this application, it refers to both the technical possibility and the actual technical implementation.

[0197] In the following, the invention will be described in detail by referring to exemplary embodiments that are accompanied by figures, in which:

[0198] FIG. 1 shows a schematic view of the covered shape-memory polymeric fiber (cSMPF) according to the present invention in a state,

[0199] FIG. 2A shows a schematic view of the covered shape-memory polymeric fiber (cSMPF) according to the present invention in a unstretched state and

[0200] FIG. 2B shows a schematic view of the covered shape-memory polymeric fiber (cSMPF) according to the present invention in a stretched state.

[0201] FIG. 3A shows a schematic representation of an illustrative semi-crystalline shape-memory polymer, which is cured using irradiation, a benzophenone initiator and a tri functional cross-linker (FG=functional group, for example ethene group)

[0202] FIG. 3B shows a schematic representation of a curing process of PEVA polymer to PEVA (covalently cross-linked PEVA) by a initiator and a cross-linker, indicating some of the potential sites for covalent cross-linking according to the current invention

[0203] FIG. 4A shows an example for a thermally-programming in laboratory setting of a shape-memory textile, comprising a covered shape-memory polymeric fiber (cSMPF)

[0204] FIG. 4B shows an example of thermally-programming on the body of a subject of a shape-memory textile comprising a covering polymer shape-memory fiber (cSMPF)

[0205] FIG. 1 illustrates an exemplary embodiment of a covered shape-memory polymeric fiber (cSMPF) having a core fiber (10) and a substantially unstretchable covering yarn (20) wound around the core fiber (10). The covering yarn (20) is wound around the core fiber (10) in a manner that the maximum engineering strain (.sub.max) of the core fiber (10) is reduced to at most the strain at the yield point (.sub.yield) of the uncovered core fiber (10).

[0206] The present invention defines a cSMPF structure, which has its purpose to prevent overstretching of the core fiber 10, causing its irreversible plastic deformation and deterioration of mechanical and shape-memory properties as well as shape.

[0207] FIGS. 2A and 2B illustrate exemplary embodiments of two states of a covered shape-memory polymeric fiber. In both states the covered shape-memory polymeric fiber has a core fiber 10 and a substantially unstretchable covering yarn 20 wound around the core fiber 10. In FIG. 2A the core fiber 10 is in a unstretched state. FIG. 2B shows the core fiber 10 in a stretched state. The change in coils/twists spacing of the covering yarn 20 upon mechanical deformation of the core fiber 10 during programming (from FIG. 2A to FIG. 2B) and recovery (from FIG. 2B to FIG. 2A) can be seen. Stretching (elongation) of the core fiber 10 having the covering yarn 20 wound around it causes the pitch, i.e. the distance between two loops of the twist, of the covering yarn 20 around the core fiber 10 to increase from r.sub.0 to r.sub.1, whereby the density of entwining (.sub.1) decreases.

[0208] FIG. 3A presents a schematic depiction of a representative semi-crystalline shape-memory polymer, demonstrating the curing process using irradiation. This process involves a phototinitiator and a tri-functional cross-linker, where each functional group (FG), such as an ethene group, actively participates in the cross-linking reaction. The diagram highlights the molecular structure of the polymer before and after the cross-linking process. It shows how the functional groups of the cross-linker interact with the polymer chains, resulting in a network structure that imparts the shape-memory properties to the polymer.

[0209] FIG. 3B offers a schematic representation of the curing process specifically for a PEVA polymer, transforming it into covalently cross-linked PEVA. This figure illustrates the various potential sites within the PEVA polymer that are susceptible to covalent cross-linking when exposed to an initiator and a cross-linker. The diagram details the structural changes at the molecular level, emphasizing the sites where cross-linking occurs, thereby enhancing the polymer's mechanical strength and shape-memory characteristics.

[0210] FIGS. 4A and 4B demonstrate the shape-memory characteristics of a shape-memory textile according to the current invention. 4A shows a thermally-programming in the laboratory, while 4B demonstrates the ability to reprogram the fiber on the body surface of a subject, due to the insolating properties of the covering yarn and the further fabric comprised by the textile.

DESIGN EXAMPLES

[0211] With reference to the following figures and examples of embodiments, the present invention will be explained in more detail without limiting the invention thereto.

[0212] The following tables list some preferred shape-memory polymers comprised by the core fiber, Sample-ID-Nos.: 1 to 20 list some preferred, but not limiting, examples of shape-memory polymers of the invention, each of which is another embodiment of the present invention.

TABLE-US-00003 TABLE 3 List of some exemplary compositions of the core fiber (SMP-1 to SMP-8, SMP-10, and SMP-17 to SMP-20) of the covered shape-memory polymeric fiber (cSMPF), PP = poly[ethylene-co-vinyl acetate] polymer (PEVAP) with 18 to 40% VA-content (as indicated by the number after the dash), PEU = amorphous multi block cycloaliphatic polyetherurethane (PEU) consisting of poly(tetramethylene glycol) (PTMEG), 1,4 butanediol (1,4-BD) and methylene bis(p-cyclohexyl isocyanate) (H12MDI), measured Gel content [%] (G) by swelling experiments in toluene, and material properties of the corresponding covered shape-memory polymeric fiber (cSMPF): E: Elastic modulus at 25 C., .sub.break: Elongation at break at 25 C.; .sub.yield: strain at yield point at 25 C.; SSR NS: shape-recovery ratio after normal stretching to 50%. BP/ SSR Sample PP-40 PP-32 PP-28 PP-18 PEU TAIC G E .sub.break .sub.yield NS ID [%] [%] [%] [%] [%] [%] [%] [MPa] [%] [%] [%] SMP-1 89 9 2 72 3.24 0.3 845 65 38 0.4 99 SMP-2 79 19 2 77 3.84 0.7 775 65 26 0.3 100 SMP-3 69 29 2 73 3.28 0.1 915 10 33 0.3 98 SMP-4 94 4 2 76 3.28 0.4 790 65 31 0.3 100 SMP-5 89 9 2 79 5.53 0.3 730 85 32 0.3 100 SMP-6 79 19 2 79 6.94 0.2 790 55 24 0.2 98 SMP-7 69 29 2 75 9.07 0.3 680 50 31 0.3 99 SMP-8 89 9 2 82 2.75 0.4 820 45 31 0.3 99 SMP-10 69 29 2 77 3.20 0.7 915 20 44 0.4 97 SMP-17 94 4 2 76 2.49 0.1 910 50 46 0.5 100 SMP-18 89 9 2 82 4.11 0.5 762 80 54 0.5 100 SMP-19 79 19 2 79 4.60 0.3 840 75 46 0.5 99 SMP-20 69 29 2 76 7.35 0.5 730 130 44 0.4 98

Example 1: Covered Shape-Memory Polymeric Fiber

[0213] In this example, the cSMPF were prepared according to a method of the invention. In the first step, the shape-memory polymer according to the invention was prepared, first, a core fiber precursor was provided:

[0214] Initially, a 50:50 mixture of initiator and cross-linker, in this case BP and TAIC is prepared. Then, this mixture is manually blended with PEVAP (poly[ethylene-co-vinyl acetate]) polymer granulates. This manual mixing ensures a preliminary and uniform distribution of the BP/TAIC mixture with the PEVA granulates.

[0215] The manually mixed materials are then compounded in a twin-screw extruder (Euro Prism Lab, Thermo Fisher Scientific, Waltham, USA). The extruder is set to a specific temperature profile: 25 C. in the feeding zone, gradually increasing to 80 C., and then maintaining 110 C. across the melting and mixing zones, before finally reaching 100 C. at the die. The screw rotation speed is controlled at 30-50 rpm, with a preference for 50 rpm. This controlled environment ensures thorough mixing and melting of the components, leading to a homogenous blend.

[0216] Following the first extrusion, the continuous filament is cut into granulates. This palletizing step transforms the extruded blend into manageable granules, facilitating further processing and handling.

[0217] The blend granulates (PEVAP+BP+TAIC) are then subjected to a second round of extrusion. This second extrusion utilizes the same temperature profile and screw rotation speed as the first, ensuring consistent and thorough mixing. The repeated extrusion process is critical to achieve an even distribution of the cross-linking agents within the polymer matrix. Similar to the first round, the extruded blend is again palletized into granulates after the second extrusion.

[0218] Finally, the granulates are dried overnight at a temperature of 40 C. This drying step is crucial to remove any residual moisture, which could potentially interfere with the subsequent curing process of the polymer.

[0219] The compounded mixture is then fed into a single screw extruder (Extrudex, Mhlacker, Germany) for extrusion. The extruder is equipped with filament dies of various diameters to produce monofilaments with the desired thickness.

[0220] The monofilaments are extruded with diameters ranging from 0.05 mm to 0.5 mm. This diameter range is chosen to provide a balance between the mechanical strength of the fibers and their flexibility.

[0221] The feeding zone is maintained at 20 C. to prevent premature melting of the mixture. The temperature is then increased to 80 C., followed by a consistent temperature of 110 C. across the melting zones. Finally, the temperature at the die is set to 100 C. This controlled temperature profile is crucial for achieving uniform melting and smooth flow of the polymer through the dies.

[0222] The screw rotation speed during extrusion is kept between 5 and 20 rpm. This range of rotation speeds allows for careful control over the extrusion process, ensuring that the monofilaments are extruded at a consistent rate and with uniform diameter.

[0223] The polymers in the core fiber or their blends can be cross-linked with covalent bonds, ionic interactions or crystallites.

[0224] The shape-memory polymer fibers were cured through inline UV irradiation, which is integrated with the fiber extrusion process. This method allows for immediate cross-linking of the fibers as they are being produced, streamlining the manufacturing process.

[0225] Covalently cross-linked polymer networks have a gel content of 60-100% according to ASTM D2765 or ISO 10147. The gel content (G) of cross-linked core fibers, more specific of the cross-linked shape-memory polymer comprised by the core fibers, was estimated by extraction in solvents such as toluene or xylene at constant temperature 110 C. Extraction time was 24 h, with another 24 h for solvent evaporation in vacuum oven at 45 C. G was calculated from the isolated weight miso of the sample and the dry weight ma after extraction using the equation below.

[00022]$G=\frac{m_d}{m_{\mathrm{iso}}}*100\%$

[0226] However, non-extracted fibers were used for covering and for investigations such as thermo-mechanical and shape-memory properties. Results of the gel content determination are listed in table 3 for different, exemplary shape-memory polymers in the spirit of the current invention.

[0227] In this specific embodiment, the selected shape-memory polymer comprised by the core fiber (10) was PEVA. Semi-crystalline cross-linked poly[ethylene-co-vinyl acetate] (cPEVA) fibers were covered with single or double covering of yarn with 750 to 3000 twists per meter. The number of twists were adjusted to allow certain deformation but to reduce the maximum engineering strain (.sub.max) of the core shape-memory polymeric fiber to at most the strain at the yield point (.sub.yield) of the uncovered core fiber.

[0228] The effect of the twist density and angle of the covering yarn on the stretchability during programming and recovery of the SMP covered yarns was evaluated.

[0229] In this exemplary embodiment, the mechanical properties of the covered and non-covered shape-memory polymeric fibers were tested by tensile testing at room as well as at elevated temperatures (below and within the broad melting transition ranges). These tensile tests were conducted on a Zwick/Roell machine Z005 (Zwick, Ulm, Germany) equipped with a thermo-chamber and temperature controller (Eurotherm Regler, Limburg, Germany) with a strain rate of 5 mm.Math.min.sup.1. The selected temperature for such measurements were 25 C., 37 C., 40 C., 50 C., 60 C., 70 C., 80 C. and 90 C.

[0230] For the exemplary covered shape-memory polymeric fibers (cSMPF) SMP-1 to SMP-8, SMP-10, SMP-17 to SMP-20 (table 3) according to this specific embodiment, several properties were determined. The elastic modulus (E) (at 25 C.) was between 2.490.1 and 9.070.3 MPa, the elongation at break (.sub.break) and stress at break (.sub.break) were obtained and analyzed. The range of elongation at break (.sub.break) was measured to be in a range between 730130% and 91520%. Shape-recovery ratio (after normal stretching to 50%) in these specific examples was determined was measured between 97% and 100%. The strain at the yield point (.sub.yield) at 25 C. was determined in a range of 240.2% to 540.5%.

[0231] Similarly, the shape-memory characteristic of the fibers were evaluated on a Zwick/Roell machine Z005 (Zwick, Ulm, Germany) equipped with a thermo-chamber and temperature controller (Eurotherm Regler, Limburg, Germany). Each shape-memory cycle within one experiment consisted of an initial programming step followed by a recovery step under stress-free conditions with heating and cooling rates 10 C..Math.min.sup.1. Each shape-memory test consisted of at least three cycles. A single step programming procedure was applied, where the sample was stretched with a rate of 10 mm min-1 to a certain programming strain (.sub.prog) at programming temperature (T.sub.prog) followed by an equilibration time of 10 min and cooling below crystallization temperature (25 C.) under constant strain. After another 10 min equilibration time, the stress was released at this lower temperature and the sample was reheated to recovery temperature (T.sub.rec). A constant force of 0.1N was applied on the specimen during recovery cycle. The T.sub.rec can be anywhere within the melting range of the polymer and can identical to T.sub.prog. The shape-fixity ratios and recovery ratio were calculated from second and third cycles and the results were analyzed.

[0232] The shape-recovery ratio for the covered fibers were 95%.

[0233] In order to ensure and evaluate long term shape-memory capability of these fibers, a test with 100 shape-memory cycles was performed which showed identical results for shape-recovery and lower shape fixity ratios over the course of 100 cycles. For practical reasons and in order to reduce the time for one cycle, the heating and cooling rates were 10 C..Math.min.sup.1 here and equilibration times were reduced to 1 min.

[0234] The foregoing are only some preferred and realizable embodiments of the present invention. Therefore, any equivalent structural modifications made by applying the description of the invention are to be included within the scope of the patent application.

[0235] Although the invention has been described and illustrated with reference to specific embodiments, the invention is not intended to be limited to these embodiments. The skilled person will recognize that variations and modifications may be made without departing from the true scope of the invention as defined by the claims and description. It is therefore intended to include within the scope of the invention all variations and modifications that fall within the scope of the appended claims and equivalents thereof.

Example 2: Shape-Memory Textile

[0236] In this particular example of the current invention, the thermal programming of a shape-memory textile incorporating covered shape-memory polymeric fibers is demonstrated using covered PEVA fibers. Initially, these fibers were programmed separately before their integration into the textile. An exemplary textile is shown in FIGS. 4A and 4B.

[0237] The programming process involved heating the shape-memory textile to 60 C. and stretching them to a low programming strain of 50%, followed by cooling to approximately 25 C. This step established the comprised shape-memory polymer fibers' temporary shape.

[0238] In this instance, the integration of thermally-programmed covered shape-memory polymeric fibers into a knitted cotton textile, achieved through weaving, serves as a specific example of the broader applicability of the techniques disclosed in the present invention. Initially, the knitted textile, with a diameter of 14 cm, incorporated these fibers. Upon exposure to a temperature of 60 C., the textile underwent significant contraction, its diameter reducing from 14 cm to 10 cm. This change was driven by the activation of the shape recovery process in the SMP fibers within the covered shape-memory polymeric fibers.

[0239] Demonstrating the versatility of this method, the shape-memory textile was subjected to a reprogramming phase. This process entailed reheating the textile to 60 C., manually expanding it to its original diameter of 14 cm, and then cooling it to 25 C. This procedure reset the covered shape-memory polymeric fibers to a new, temporarily held shape. When reheated to 60 C., the textile consistently returned to a diameter of 10 cm. This cycle of reprogramming and recovery was successfully replicated five times, emphasizing the durability and reliability of the shape-memory effect in the textile.

[0240] An important feature of this example is the insulating property of the textile's cotton component. This insulation ensures safe heating of the SMP fibers for shape recovery, maintaining safety even when the textile is worn. Notably, while the initial programming of the shape-changing fibers, in this case exemplified by PEVA fibers, occurred before their incorporation into the textile, subsequent cycles involved reprogramming the entire textile, including the integrated SMP fibers. This highlights the flexibility of the programming process, which is effective both for individual covered shape-memory polymeric fibers and the composite shape-memory textile comprising the same. Furthermore, this demonstrates the thermally programmable nature of the employed textile for fitting and adjusting purposes directly on a subjects body.

[0241] This example underscores the innovative potential of thermally programmable shape-memory textiles in creating dynamic and adaptable fabrics. It opens up possibilities for their application in various domains, such as adjustable clothing or medical textiles. These applications benefit from the textile's ability to conform to changing shapes and offer a definable and reprogrammable compression force, directly related to the programmed strain.

REFERENCE LIST

[0242] (1) Covered shape-memory polymeric fiber (cSMPF) [0243] (10) Core fiber [0244] (20) Unstretchable covering yarn [0245] (30 Semi-crystalline shape-memory polymer [0246] (31) Crystalline rigid segment [0247] (32) Switching segment [0248] (40 covalently cross-linked shape-memory polymer [0249] (50) radicals [0250] (60) Initiator [0251] (61) Cross-linker