Heatable Garment, Fabrics for Such Garments, and Methods of Manufacture

Abstract

The present invention relates to heatable garments, comprising a garment body and a heating pad adhered to at least a portion of the garment body, wherein the heating pad comprises graphene particles dispersed in a polymer matrix material. The invention also provides fabrics for making such garments, and methods of making such garments and fabrics. Also provided are heatable bedding incorporating a heating pad as described above.

Claims

1. A heatable garment, comprising a garment body and a heating pad adhered to at least a portion of the garment body, wherein the heating pad comprises graphene particles dispersed in a polymer matrix material.

2. A heatable garment according to claim 1, wherein the heating pad is a heatable coating bonded directly or indirectly to the garment body.

3. A heatable garment according claim 1, wherein the graphene particles are graphene nanoplatelets.

4. A heatable garment according to claim 3, wherein the graphene nanoplatelets have an average of 2 to 100 graphene layers per particle.

5. A heatable garment according to claim 3, wherein the graphene nanoplatelets have an average of 2 to 5 graphene layers per particle.

6. A heatable garment according to claim 1, wherein the graphene particles are functionalised graphene particles.

7. A heatable garment according to claim 6, wherein the graphene particles are oxygen-functionalised, hydroxy-functionalised, carboxy-functionalised, carbonyl-functionalised, amine-functionalised, amide-functionalised or halogen functionalised.

8. A heatable garment according to claim 1, wherein the heating pad comprises multiple stacked layers of conductive material.

9. A heatable garment according to claim 1, wherein the average thickness of the heating pad is 300 μm or less.

10. A heatable garment according to claim 1, wherein the polymer matrix material is an elastic material.

11. A heatable garment according to claim 1, further comprising an electrically-insulating covering layer, overlaying and bonded to the heating pad.

12. A heatable garment according to claim 11, wherein the electrically-insulating covering layer is formed from an elastic material.

13. A heatable garment according to claim 11, wherein the electrically-insulating covering layer is made from polyurethane or silicone.

14. A heatable garment according to claim 1, wherein the heating pad is adhered directly to the garment body.

15. A heatable garment according to claim 1, wherein the heating pad is indirectly adhered to the garment body, with the heating pad adhered to an intermediate layer which is itself adhered to the garment body.

16. A heatable garment according to claim 15, wherein the intermediate layer is made from polyurethane.

17. A heatable garment according to claim 1, comprising a temperature control system, to control the temperature of the heating pad.

18. A heatable garment according to claim 17, wherein the heatable garment comprises two or more of said heating pads, and the control system is configured to allow independent control over the temperature of each heating pad.

19. A heatable garment according to claim 18, comprising two or more of said heating pads which target different muscle groups, wherein the control system is configured to allow the temperature of the heating pads to be independently adjusted according to the muscle group.

20. A heatable garment according to claim 1, wherein the garment is a pair of a; trousers or shorts.

21. A heatable garment according to claim 1, wherein the garment is a top.

22. A heatable garment according to claim 1, wherein the garment is a strap.

23. A method of making a heatable garment according to claim 1, comprising: providing a clothing material; and depositing one or more layers of a conductive material onto at least a portion of the clothing material to form a heating pad; wherein the conductive material comprises graphene particles dispersed in a polymer matrix material.

24. A method according to claim 23, comprising: providing said clothing material; depositing a conductive ink onto at least a portion of the clothing material and allowing the ink to at least partially permeate into the clothing material; removing excess ink from the clothing material; curing the ink so as to form a first layer of said conductive material; and optionally depositing further layers of said conductive material on the first layer of conductive material.

25. A method according to claim 23, comprising: providing said clothing material; depositing a solvent onto at least a portion of the clothing material and allowing the solvent to at least partially permeate the clothing material so as to form a wetted clothing material; depositing a conductive ink onto the wetted clothing material; optionally, allowing the ink to at least partially permeate the clothing material; removing excess ink from the clothing material; and curing the ink so as to form a first layer of said conductive material; and optionally depositing further layers of said conductive material on the first layer of conductive material.

26. A method according to claim 23, comprising: providing said clothing material; depositing an electrically-insulating layer onto at least a portion of the clothing material; and depositing one or more layers of said conductive material onto the electrically-insulating layer.

27. A method according to claim 23, further comprising depositing an electrically-insulating covering layer onto said one or more layers of conductive material.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0177] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0178] FIGS. 1A and 1B are respectively front and rear views of a long-sleeved sports vest according to the present invention, having heating pads adhered to the wrist area and back of the garment;

[0179] FIGS. 2A and 2B are respectively front and rear views of a wristband according to the present invention;

[0180] FIGS. 3 and 4 are cross-sectional views of a garment of the present invention, showing a woven fabric over-printed with conductive ink;

[0181] FIG. 5 is a cross-sectional view of a garment of the present invention showing a woven fabric over-printed with conductive ink which has permeated through the fabric and the individual yarns making up that fabric;

[0182] FIG. 6 is a cross-sectional view of a garment of the present invention showing a woven fabric over-printed with a two-layer heating pad which has permeated through the fabric, but not the individual yarns making up the fabric;

[0183] FIG. 7 is a cross-sectional view of a garment of the present invention having a heating pad encapsulated within an electrically-insulating silicone layer;

[0184] FIG. 8 is a cross-sectional view of a garment of the present invention having a heating pad printed onto an intermediate silicone layer;

[0185] FIG. 9 is a cross-sectional view of a garment of the present invention having a heating pad encapsulated within a thermoplastic polyurethane layer;

[0186] FIG. 10 is a plot showing the effect of increasing the number of layers of conductive ink on sheet resistance;

[0187] FIG. 11 is a plot showing the effects of adding silver contacts on the heating pads;

[0188] FIGS. 12 and 13 show the temperature achieved by heating pads on different fabrics both before (FIG. 12) and after (FIG. 13) being subjected to deformation; and

[0189] FIG. 14 shows the effects of using different printing techniques on the performance of the heating pads.

DETAILED DESCRIPTION

[0190] FIGS. 1 and 2 show garments according to the present invention, which are capable of heating a user's blood via the anterior portion of the wrist.

[0191] FIG. 1A shows a long-sleeved sports vest 1 formed from a lightweight flexible fabric base material 3 (the garment body). The wrist area on each arm of the vest includes heating pads 5 which are positioned so as to overlay the anterior portion of the wrist during normal use. The heating pads 5 have been formed by coating a single layer of conductive ink (comprising graphene nanoplatelets dispersed in a polymer binder and solvent) onto the relevant portion of the outside of the garment, and allowing the ink to cure. The heating pads are covered with a layer of silicone elastomer to improve the thermal properties of the ink, and electrically insulate the wearer from the heating pad.

[0192] The heating pads are linked to a button-type battery 9 on the rear of the garment via conductive tracks 7, as shown in FIG. 1B. In this case, the tracks are formed from the same conductive ink used to form the heating pad, but they could alternatively be formed from silver tracks, or by stitching conductive wire (e.g. copper wire) into the fabric material. The rear of the garment also includes a back heating pad 11 of identical construction to heating pad 5, connected to the same battery via carbon tracks 13.

[0193] FIGS. 2A and 2B show a heatable wrist-band 101 formed from a flexible and stretchable fabric base material 103. The front of the wrist-band (shown in FIG. 2A), positioned over the anterior portion of a user's wrist in use, includes a heating pad 105, connected to a button-type battery on the rear of the wrist-band (shown in FIG. 2B) via conductive traces 107. The heating pad is formed in an identical fashion to the heating pads in the vest of FIGS. 1A and 1B, and overlaid with a silicone encapsulating layer in the same way.

[0194] FIGS. 3 to 7 provide close-up cross-sectional views of a woven fabric, showing different constructions of the heatable garment of the present invention in which a conductive ink is bonded directly to the fabric.

[0195] FIG. 3 shows a non-permeable fabric having warp yarns 203 and weft yarns 205, overcoated with a heating pad formed from a single layer of conductive ink 207. FIG. 4 shows the same construction as FIG. 3, but with a significantly thicker layer of conductive ink 207a. FIG. 5 shows a layer of conductive ink 207b coated onto a permeable fabric, where the conductive ink 207b has been allowed to soak through the fabric and into the individual yarns of the fabric before curing, creating a strong bond between the conductive ink 207b and the fabric. FIGS. 6 and 7 show further alternative construction, in which a layer of conductive ink 207c has been allowed to soak through the fabric before curing (but has not penetrated the individual yarns), and then coated with a second layer of conductive ink 209 (FIG. 6) or an encapsulating silicone layer 211 (FIG. 7).

[0196] FIG. 8 provides a close-up cross-sectional view of a woven fabric, in which a fabric has been covered with a layer of polymer 213 (an “intermediate” layer) before coating with a single layer of conductive ink 207d. In this case, the conductive layer 207d is indirectly bonded to the underlying fabric substrate. FIG. 9 shows a similar arrangement to FIG. 8 in which a first layer of polymer 213 (an intermediate layer) has been allowed to permeate into the fabric before coating with conductive ink 207d, followed by addition of a further layer of polymer 215 (an electrically-insulating covering layer). In this way, the conductive ink layer 207d is entirely encapsulated within the polymer. In this particular embodiment, the polymer 213 and polymer 215 are both thermoplastic polyurethane.

EXPERIMENTAL RESULTS

Example 1

[0197] In a first set of experiments, the viability of printing conductive ink directly onto fabric was evaluated.

[0198] A high percentage conductive ink containing carbon nanoparticles including functionalised graphene nanoplatelets (GNPs) (Haydale Graphene Industries plc) was bar coated onto a cotton textile to assess whether the ink would still be conductive when printed.

[0199] The textile was stretched and fixed into place using tape to minimise stretching during the printing process. A single layer of ink was applied, and the sample was subsequently removed and dried in an oven. Once dried a voltmeter was used to test the conductivity of the sample. The presence of a resistance proved that the ink was conductive. The sample was crumpled and then retested. It remained conductive.

[0200] These results showed that conductive carbon ink can be successfully printed onto a textile and can survive crumple testing and stretching.

Example 2

[0201] In a second set of experiments, the effect of carbon loading on performance was assessed.

[0202] A “higher carbon content” heatable fabric was produced by bar coating cotton fabric swatches with a conductive ink containing carbon nanoparticles including functionalised GNPs (Haydale Graphene Industries plc). The ink was allowed to dry in an oven at 100° C., and then overprinted with a further ink layer. This process was repeated to produce a three-layered heating pad on a polyester/cotton blend fabric (67% polyester/33% cotton).

[0203] Next, the conductive ink was diluted with polyester thermoplastic polyurethane polymer to decrease the carbon content, and “lower carbon content” heatable fabric was produced using the same protocol as for the “high carbon content” fabric.

[0204] In both cases, the resulting samples were flexible fabrics that conducted electricity, having resistance values as follows:

TABLE-US-00001 TABLE 1 Resistance (kΩ) Example 2A (Higher carbon content ink) 0.09 Example 2B (Lower carbon content ink) 77.2

[0205] This showed that the higher carbon content ink was significantly more conductive than the lower carbon content ink.

Example 3

[0206] In a third set of experiments, the effect of the fabric substrate on the measured resistance value was assessed. The protocol for making the “lower carbon content ink” sample of Example 2 was repeated using a cotton material, which was thinner than the polyester/cotton fabric, and has a lower denier fibre and lower thread count. The resulting sample displayed considerably higher resistance, as shown in Table 2:

TABLE-US-00002 TABLE 2 Resistance (kΩ) Example 2B (Thicker fabric) 77.2 Example 3A (Thinner cotton fabric) 273.1

Example 4

[0207] In a fourth set of experiments, the impact of the number of layers on resistance was evaluated.

[0208] A cotton substrate was ironed and secured to a surface before being screen-printed with the high carbon content ink using a 54-64 mesh. The resulting coated substrate was passed through an oven at 100° C. five times. This process was repeated to build up further layers where appropriate, with care taken to ensure registration between layers. The sheet resistance of the samples was then measured using a four-point probe.

[0209] The results, shown in FIG. 10, demonstrate that the sheet resistance decreased as the number of layers increased, with the most significant drop in resistance being observed between one-layer and two-layer samples.

Example 5

[0210] In a fifth set of experiments, the effect of providing silver tracks on the resistivity of the heating pad was assessed.

[0211] Heating pads were formed on polyester (100% polyester) substrates or polyester/cotton blend (66% polyester/33% cotton) substrates. The pads were made by screen-printing 3, 4 or 5 layers of conductive ink in the form of 5×5 cm blocks, with the samples passing through an oven five times at 100° C. after each layer was applied. To provide electrical contacts, silver tracks were applied to opposing ends of the square blocks by a stencil painting method. The resistance of the resulting heating pads is shown in FIG. 11.

[0212] This shows that the provision of the silver contacts reduced the resistivity of the samples by ˜8Ω, due to the improved electron flow into the heating pads.

Example 6

[0213] In a sixth set of experiments, the effect of providing an electrically-insulating covering was assessed.

[0214] Heating pads were formed on polyester, polyester/cotton blend (67% polyester, 33% cotton) or nylon substrates. The pads were made by applying multiple layers of conductive ink in the form of 5×5 cm blocks using either screen-printing or bar-coating, with the samples passing through an oven five times at 100° C. after each layer was applied. Silver tracks were applied to opposing ends of the square blocks by a stencil painting method, to provide electrical contacts with the heating pad. Finally, electrically insulating layers of silicone or polyurethane were applied over the heating pad and/or on the back face of the fabric, underlying the heating pad. The exact samples created are summarised in Table 3:

TABLE-US-00003 TABLE 3 Insulating Insulating layer on Number of layer opposite side conductive Coating overlaying of fabric to Example Fabric layers method* heating pad heating pad 6A Polyester 3 SP Polyurethane — 6B Polyester 4 SP Silicone — 6C Polyester 4 SP — Polyurethane 6D Polyester 5 SP Silicone — 6E Polyester/ 4 SP Silicone Silicone Cotton 6F Nylon 1 BC Silicone — *SP = screen-printed, BC = bar-coated

[0215] The samples were then supplied with power from a 3V source via the silver contacts, and the temperature of the samples monitored using a thermal imaging camera. The peak temperature was measured every 30 seconds to assess the heating performance of the samples. The resulting resistance values are shown in FIG. 12.

[0216] The results show that all of the heaters reached temperatures of over 35° C. from a voltage of 3V within the first 30 seconds of power supply, and all eventually reached the target temperature of 37° C. (human body temperature—indicated by a straight line in FIG. 12) within 90 seconds. The rate of temperature increase means that the garments formed from the fabric would reach useful temperature relatively rapidly, but not so rapidly that the user would be unable to react if the heating pad became uncomfortably hot, thus decreasing the danger of burns occurring. The best performing heaters were all silicone encapsulated, and had 4 layers of ink. The images from the thermal imaging camera showed a relatively even temperature distribution across each heating pad.

[0217] Next, the samples were subjected to deformation by bending them by hand across an 8 cm diameter circular bar 200 times, to simulate the kinds of strain a garment might be subjected to during use. The resistance values were then measured again, and compared with the pre-deformation values to assess the impact of deformation on the thermal performance. The resulting resistance values are shown in FIG. 13, and a comparison with the pre-deformation values is shown in Table 4:

TABLE-US-00004 TABLE 4 Temperature Difference Maximum Maximum [post- Resistance Resistance temperature temperature deformation- pre- post- pre- post- pre- deformation deformation deformation deformation deformation] Example (Ω) (Ω) (° C.) (° C.) (° C.) 6A 8.4 8.4 38.7 40.1 1.4 6B 6.4 6.2 49.5 44.5 −5 6C 6.2 6.5 40.3 34.9 −5.4 6D 4.5 4.9 56.6 56.3 −0.3 6E 5.1 6 53.6 51.1 −2.5 6F 8 8 39.8 37.1 −2.7

[0218] The deformation of the heaters resulted in a slight reduction in the maximum temperature achieved, except for Sample 6A which showed a slight increase in the temperature achieved. For silicone encapsulated samples, 6A, and 6D-6F, the deformation had little effect on the uniformity of the temperature profile across the heater, although slightly bigger drops in uniformity were observed for samples 6B-6C.

[0219] These results show that it is possible to print single or multi-layer heating pads onto fabric, and that such heating pads can achieve uniform temperatures around human body temperature upon application of modest voltages. The results also show that encapsulating the heating pad in an elastic material can improve thermal performance, and improve the robustness of the heating pad to deformation.

Example 7

[0220] In a seventh set of experiments, the effect of using different printing techniques was assessed.

[0221] Fabrics (either 100% polyester, or 66% polyester/33% cotton blend) were printed with a conductive ink using a 5 cm×5 cm×100 μm stencil. The ink was deposited within the space in the stencil, excess ink was removed by drawing a block across the stencil, and then the ink was dried in an oven at 130° C. for 5 minutes to form a heating pad. The fabrics were printed whilst held in a stretched state using adhesive tape. The resulting cured ink blocks were then printed with silver lines along opposing sides of the block. The ink layers all displayed good uniformity, showed good flexibility and resistance to cracking when stretched.

[0222] Three different types of printing were carried out:

[0223] (i) Hand-Printing on Both Sides of the Fabric: [0224] A first layer of conductive ink was applied to the fabric and allowed to dry at 130° C. for 5 minutes. The fabric was then turned over and printed with a second layer of conductive ink which directly overlay the first layer on the opposite side of the fabric.

[0225] (ii) Ink Soaking Technique [0226] A thick layer of ink was deposited on the fabric within the stencil using a spatula, and allowed to soak into the fabric for 5 minutes before excess was removed, and the ink dried.

[0227] (iii) Solvent Soaking Technique: [0228] The fabric was soaked with diacetone alcohol and printed with the conductive ink whilst still damp. This helped the conductive ink to soak into the fabric during printing, such that the conductive ink soaked all the way through the fabric.

TABLE-US-00005 TABLE 5 Example Fabric Printing type 7A Polyester Both sides 7B Polyester Both sides 7C Polyester/Cotton Both sides 7D Polyester/Cotton Both sides 7E Polyester Ink soak 7F Polyester/Cotton Ink soak 7G Polyester Solvent soak

[0229] The heating pads were connected to a 3V power supply via the silver lines (in the case of the fabrics printed on both sides, only one layer of the conductive block was connected to the power source). The temperature of the heating pads during application of electrical power was monitored as in Example 6, resulting in the results shown in FIG. 14.

[0230] The results showed that all of the examples were capable of achieving temperatures above 35° C. from a 3V power source.

[0231] The results showed that the fabrics which had been soaked with either ink or solvent before printing heated more rapidly than those which had not been soaked, and attained higher temperatures. The fabrics which were printed on both the front and back did not appear to display any interaction between the layers on different sides of the surface.

[0232] These results show that soaking the fabric with either ink or solvent before printing resulted in improved performance, without an increase in the overall bulk of the fabric, and without adversely affecting mechanical properties.

[0233] In respect of numerical ranges disclosed in the present description it will of course be understood that in the normal way the technical criterion for the upper limit is different from the technical criterion for the lower limit, i.e. the upper and lower limits are intrinsically distinct proposals.

[0234] For the avoidance of doubt it is confirmed that in the general description above, in the usual way the proposal of general preferences and options in respect of different features of the heatable garments, fabrics and bedding and methods described above constitutes the proposal of general combinations of those general preferences and options for the different features, insofar as they are combinable and compatible and are put forward in the same context.

[0235] The terminology above used in relation to garments and bedding is based on normal U.K. English usage, and the skilled reader will understand that certain of the above items may be given different names in other English-speaking countries, such as the U.S.A.