ADDITIVE MANUFACTURING PROCESS FOR COMPOSITIONS COMPRISING POLY-ARYL-ETHER-KETONE(S)

Abstract

The invention relates to an additive manufacturing process by extrusion for forming a three-dimensional part in an additive manufacturing machine having a build environment, the process comprising: i) providing a composition comprising at least one poly-aryl-ether-ketone (PAEK) having a melt viscosity from about 200 Pa.Math.s to about 1500 Pa.Math.s, according to ASTM D3835-16, measured at a temperature of 320° C. and at a shear rate of 100 s.sup.−1, by capillary rheology using a 1 mm diameter, 15 mm long die; ii) extruding the composition in the build environment at an extrusion temperature equal to 330° C. or less, to form an extruded part section; and, iii) cooling the extruded part section in the build environment.

The invention also relates to a filament and its use in said additive manufacturing process and the corresponding object obtainable from said additive manufacturing process.

Claims

1. An additive manufacturing process by extrusion for forming a three-dimensional part in an additive manufacturing machine having a build environment, the process comprising: i) providing a composition comprising at least one poly-aryl-ether-ketone (PAEK) having a melt viscosity from about 200 Pa.Math.s to about 1500 Pa.Math.s, according to ASTM D3835-16, measured at a temperature of 320° C. and at a shear rate of 100 s-1, by capillary rheology using a 1 mm diameter, 15 mm long die; ii) extruding the composition in the build environment at an extrusion temperature equal to 330° C. or less, to form an extruded part section; and, iii) cooling the extruded part section in the build environment.

2. The additive manufacturing process of claim 1, wherein the melt viscosity of the composition is from about 400 to about 1100 Pa.Math.s, as measured at a temperature of 320° C. and at a shear rate at 100s-1 by capillary rheology using a 1 mm diameter, 15 mm long die.

3. The additive manufacturing process of claim 1, wherein the composition is extruded at a temperature of 325° C. or less.

4. The additive manufacturing process of claim 1, wherein the melt temperature of the composition is from about 290° C. to about 320° C., as measured according to ISO 11357, section 3.

5. The additive manufacturing process of claim 1, wherein the composition has a crystallization half-time at Tg+55° C., as measured according to ISO 11357, section 7: from about 1 minute to about 60 minutes; wherein Tg is the glass transition temperature of the composition, as measured according to ISO 11357, section 2.

6. The additive manufacturing process of claim 1, wherein the additive manufacturing machine does not contain any means for actively heating the build environment.

7. The additive manufacturing process of claim 1, wherein the temperature of the build environment during the process does not exceed 85° C.

8. The additive manufacturing process of claim 1, wherein the additive manufacturing machine comprises a print bed placed in the build environment, which is suitable for supporting the three-dimensional part under construction and suitable for adhering to it, wherein the temperature of the print bed being during at least part of the process is: from about Tg−60° C. to about Tg+5° C.; wherein Tg is the glass transition temperature of the composition, as measured according to ISO 11357, section 2.

9. The additive manufacturing process of claim 1, wherein the at least one poly-aryl-ether-ketone represents at least 50% to up to 100% by weight of the composition.

10. The additive manufacturing process of claim 1, wherein the at least one poly-aryl-ether-ketone is a random poly-ether-ketone-ketone copolymer which consists essentially of two monomeric units having the formula: ##STR00004## wherein the copolymer has a T:1 ratio from 55:45 to 65:35.

11. The additive manufacturing process of claim 1, wherein the at least one poly-aryl-ether-ketone is a poly[(ether-ether-ketone)-ran-(ether-biphenyl-ether-ketone)] which consists essentially of monomeric units having the formula: unit(s) of formula: Ph-O-Ph-O-Ph-C(O)— and, unit(s) of formula: Ph-O-Ph-Ph-O-Ph-C(O)—, wherein Ph is a phenylene group and —C(O)— is a carbonyl group, wherein each one of the phenylene groups may independently be ortho-, meta- or para-substituted.

12. The additive manufacturing process of claim 10, wherein the composition has an inherent viscosity, as measured according to ISO 307 in an aqueous solution of 96% by weight sulfuric acid at 25° C., from about 0.1 to about 0.7 dL/g.

13. The additive manufacturing process of claim 1, wherein the composition consists essentially of: the at least one poly-aryl-ether-ketone; and, optionally one or more fillers and/or additives.

14. The additive manufacturing process of claim 1, wherein the crystallinity of the three-dimensional part obtained at the end of the process does not exceed 5% wt as measured by X-Ray diffraction.

15. The additive manufacturing process of claim 1, wherein the average coefficient of linear thermal expansion is equal to about 6.10-5 K-1 or less, measured between 20° C. and the glass transition temperature of the composition, according to ISO 11359-2.

16. Filament comprising a composition comprising at least one poly-aryl-ether-ketone (PAEK), wherein the melt viscosity of the composition is from about 200 Pa.Math.s to about 1500 Pa.Math.s, according to ASTM D3835-16, measured at a temperature of 320° C. and at a shear rate of 100 s-1, by capillary rheology using a 1 mm diameter, 15 mm long die.

17. Use of a filament according to claim 16 in an additive manufacturing process by extrusion for forming a three-dimensional part, wherein the extrusion temperature is equal to 330° C. or less.

18. An object obtainable by the additive manufacturing process of claim 1.

Description

DESCRIPTION OF PREFERRED EMBODIMENTS

Composition Comprising on Poly-aryl-ether-ketone(s)

[0057] The poly-aryl ether ketone(s) (PAEK(s)) of the composition according to the invention comprise(s) units of the following formulas:

(—Ar—X—) and (—Ar.sub.1—Y—),

wherein: [0058] Ar and Ar.sub.1 each denote a divalent aromatic radical; Ar and Ar.sub.1 may be preferably selected from 1,3-phenylene, 1,4-phenylene, 4,4′-biphenylene, 1,4-naphthylene, 1,5-naphthylene and 2,6-naphthylene; [0059] X designates an electron-withdrawing group; X may be preferably selected from a carbonyl group and a sulfonyl group; and [0060] Y designates a group selected from an oxygen atom, a sulphur atom, an alkylene group, such as —CH.sub.2— and isopropylidene.
In these units X and Y, at least 50 percent, preferably at least 70 percent, and more particularly at least 80 percent of the groups X are a carbonyl group, and at least 50 percent, preferably at least 70 percent, and more particularly at least 80 percent of the groups Y represent an oxygen atom. According to a preferred embodiment, 100 percent of the groups X denote a carbonyl group and 100 percent of the groups Y denote an oxygen atom.

[0061] The composition according to the invention comprises PAEK(s). The weight of PAEK or, if relevant, the sum of the weights of PAEKs of the composition, generally represents at least 50% of the total weight of the composition. In some embodiments, the weight of poly-aryl-ether-ketone(s) may represent at least 60%, or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 92.5%, or at least 95%, or at least 97.5%, or at least 98%, or at least 98.5%, or at least 99% or at least 99.5% of the total weight of the composition. In some specific embodiments, the composition consists essentially of, preferably consisting of PAEK(s): the weight of PAEK(s) represents approximately 100% of the total weight of composition.

[0062] Advantageously, the PAEK(s) in the composition may be chosen from: [0063] a poly-ether-ketone-ketone, also noted “PEKK”; a PEKK comprises one repeating unit or more of formula: -Ph-O-Ph-C(O)-Ph-C(O)—; [0064] a poly-ether-ether-ketone, also noted “PEEK”; a PEEK comprises one repeating unit or more of formula: -Ph-O-Ph-O-Ph-C(O)—; [0065] a poly-ether-ketone, also noted “PEK”; a PEK comprises one repeating unit or more of formula: -Ph-O-Ph-C(O)—; [0066] a poly-ether-ether-ketone-ketone, also noted “PEEKK”; a PEEKK comprises one unit or more of formula: -Ph-O-Ph-O-Ph-C(O)-Ph-C(O)—; [0067] a poly-ether-ether-ether-ketone, also noted “PEEEK”; a PEEEK comprises one unit or more of formula: -Ph-O-Ph-O-Ph-O-Ph-C(O)—; [0068] a poly-ether-diphenyl ether-ketone also called PEDEK; a PEDEK comprises a unit (s) of formula: a PEDEK comprises a unit (s) of formula —Ph-O-Ph-Ph-O-Ph-C(O)—; [0069] their blends; and/or [0070] their copolymers;
wherein Ph represents a phenylene group and —C(O)— a carbonyl group, each of the phenylenes being independently ortho- (1-2), meta- (1-3) or para- (1-4) substituted, preferentially meta- or para-substituted.

[0071] In addition, defects, end groups and/or monomers may be incorporated in a very small amount in the polymers as described in the above list, without affecting their performance.

[0072] In some embodiments, the composition comprises at least one PEKK. The PEKK may be a copolymer, in particular a random copolymer, comprising, preferentially consisting essentially of, and more preferably consisting of isophthalic units (“I”), of formula:

##STR00002##

and,
terephthalic units (“T”), of formula:

##STR00003##

[0073] The molar ratio of terephthalic unit to isophthalic and terephthalic units (T:T+I) may be from 0 to 5%; or 5 to 10%; or 10 to 15%; or 15 to 20%; or 15 to 20%; or from 20 to 25%; or 25 to 30%; or from 30 to 35%; or 35 to 40%; or 40 to 45%; or 45 to 50%; or 50 to 55%; or 55 to 60%; or 60 to 65%; or 65 to 70%; or 70 to 75%; or 75 to 80%; or 80 to 85%; or 85 to 90%; or 90 to 95%; or 95 to 100%. The choice of the molar ratio of T units relative to the sum of T and I units makes it possible to adjust the melt temperature of PEKK and its crystallization rate at a given temperature. A random PEKK copolymer with a specific T:I ratio may be produced by adjusting the respective concentrations of the reactants during the polymerization, in a manner known per se.

[0074] Advantageously, the composition may comprise at least one PEKK having a T:I ratio from 55:45 to 65:35. Indeed, for this range of T:I ratio, the melt temperature is less than 330° C. and the crystallization half-time of PEKK at 215° C., as measured according to ISO 11357, section 7, is from about 5 minutes to about 30 minutes. In particular, the PEKK copolymer may have a T:I ratio of from 58:42 to 62:38 and preferably of about 60:40.

[0075] In some embodiments, the composition may comprise a blend of different random copolymers of PEKKs. In particular, the composition may comprise a mixture of different copolymers of PEKKs having different T:I ratios. The composition may also comprise a mixture of different copolymers of PEKKs having different viscosities. Finally, the composition may also comprise a mixture of different copolymers of PEKKs having both different T:I ratios and different viscosities.

[0076] In some embodiments, the composition comprises at least one PEEK-PEDEK copolymer. The PEEK-PEDEK may be a copolymer, in particular a random copolymer, comprising, preferably consisting essentially of, and more preferably consisting of: [0077] unit(s) of formula: Ph-O-Ph-O-Ph-C(O)— (III); and, [0078] unit(s) of formula: Ph-O-Ph-Ph-O-Ph-C(O)— (IV);
wherein Ph is a phenylene group and —C(O)— is a carbonyle group, wherein each one of the phenylene groups may independently be ortho-, meta- or para-substituted, preferentially meta- or para-substituted.

[0079] The molar ratio of repeating unit (III) to units (III) and (IV) (III:III+IV) in the PEEK-PEDEK may be of from 0 to 5%; or 5 to 10%; or 10 to 15%; or 15 to 20%; or 15 to 20%; or from 20 to 25%; or 25 to 30%; or from 30 to 35%; or 35 to 40%; or 40 to 45%; or 45 to 50%; or 50 to 55%; or 55 to 60%; or from 60 to 65%; or from 65 to 70%; or 70 to 75%; or from 75 to 80%; or from 80 to 85%; or from 85 to 90%; or from 90 to 95%; or from 95 to 100%. The choice of the molar ratio of unit (III) to units (III) and (IV) makes it possible to adjust the melt temperature of PEEK-PEDEK and its crystallization rate at a given temperature. A random PEEK-PEDEK copolymer with a specific ratio of repeating unit (III): repeating unit (IV) may be produced by adjusting the respective concentrations of the reactants during the polymerization, in a manner known per se.

[0080] In some embodiments, the composition comprises a blend of different copolymers of PEEK-PEDEKs. In particular, the composition may comprise a mixture of different copolymers of PEEK-PEDEKs having a different molar ratio of repeating unit (III): repeating unit (IV). The composition may also comprise a mixture of different copolymers of PEEK-PEDEKs having a different melt viscosity. Finally, the composition may comprise a mixture of different copolymers of PEEK-PEDEKs having a different molar ratio of repeating unit (III): repeating unit (IV) and a different melt viscosity.

[0081] In some embodiments, the composition comprises at least two types of PAEKs, more particularly a PEKK, and in addition to the PEKK, at least one of the following polymers: PEK, PEEKEK, PEEK, PEEKK, PEKEKK, PEEEK, PEDEK, and PEEK-PEDEK. The polymer(s) in addition to the PEKK may represent less than 50% by weight of the total weight of the composition, and preferably less than 30% by weight of the composition.

[0082] The composition may especially comprise a mixture of PEEK(s) and PEKK(s), wherein PEEK essentially consists of, preferably consists of: repeating units of formula (III), and wherein PEKK essentially consists of, preferably consists of, isophthalic and terephthalic units. The advantage to combine a PEEK with a PEKK, especially a PEKK having a T:T+I ratio of less than 65%, or less than 55%, or less than 45%, is that it enables to accelerate the crystallization rate of the composition, compared to the crystallization rate of the same PEKK considered alone, at a given temperature. Conversely, the advantage of associating a PEKK with a PEEK, especially a PEKK having a T:T+I ratio of less than 65%, or less than 55%, or less than 45%, is that it enables to slow down crystallization rate of the composition compared to the crystallization rate of the PEEK considered alone, at a given temperature.

[0083] The melt viscosity of the composition at 320° C. and at a shear rate of 100 5.sup.−1, by capillary rheology using a 1 mm diameter, 15 mm long die, is from about 200 to about 1500 Pa.Math.s. The range of melt viscosities of the composition comprising at least one poly-aryl-ether-ketone (PAEK) enables to carry out the process at a relatively low extrusion temperature, namely a temperature equal to 330° C. or less, and at a relatively low build environment temperature. This selection corresponds to unusual conditions compared to what is generally carried out in typical processes used until now, which typically perform better at a higher extrusion temperature than the one claimed herein. A three-dimensional part having a correct dimensioning and substantially no warping may be obtained. The melt viscosity of the composition is from about 400 to about 1100 Pa.Math.s, as measured at a temperature of 320° C. and at a shear rate at 100s.sup.−1 by capillary rheology using a 1 mm diameter, 15 mm long die.

These viscosities may be obtained by having a composition comprising, if relevant, a melt viscosity-controlling agent in addition to the major PAEK, in molar proportion. The melt viscosity-controlling agent may be another PAEK having a different melt viscosity than the major PAEK. The composition may comprise additives or fillers as described below in order to increase its melt viscosity. The composition may comprise a plasticizer in order to reduce its melt viscosity. Plasticizers compatible with many PAEKs, in particular PEKKs, are, for example, diphenylsulfone or 1,4-bis (4-phenoxybenzoyl)benzene.

[0084] The composition may have an inherent viscosity, as measured according to ISO 307 in an aqueous solution of 96% by weight sulfuric acid at 25° C., from about 0.1 dL/g to about 0.7 dL/g, preferably from about 0.15 to about 0.5 dL/g, and more preferably of from about 0.2 to about 0.4 dL/g. In particular, the composition may essentially consist of, preferably consist of, PEKK(s) having a T:T+1 ratio of from 55% to 65%, and have an inherent viscosity, of from 0.1 dL/g to 0.7 dL/g.

[0085] The half-crystallization time of the composition at Tg+55° C. may be of from about 1 minute to about 60 minutes. If the crystallization half-time of the composition at Tg+55° C. is more than about 60 minutes, any post print crystallization process would be prohibitively long. If the crystallization half-time of the composition at Tg+55° C. is less than about 1 minute, it may crystalize upon cooling, resulting in warping or poor layer adhesion. Advantageously, the crystallization half-time of the composition at Tg+55° C. is from about 3 minutes to about 45 minutes and preferably from about 5 minutes to about 30 minutes.

[0086] A composition having such crystallization half-time at Tg+55° C. may be obtained by including in the composition a crystallization rate-controlling agent, if relevant, in addition to the major PAEK, in molar proportion. The composition may contain an amorphous polymer in order to slow down its crystallization rate at Tg+55° C. The amorphous polymer may be a PAEK or not. An amorphous polymer compatible with many PAEKs, in particular PEKK, is for instance a polyetherimide. The composition may contain one or more filler(s)/additive(s), as described below, acting as nucleant(s), in order to increase its crystallization rate at Tg+55° C.,

[0087] The composition may be semi-crystalline. It may have a melt temperature equal to about 325° C. or less, preferably equal to about 320° C. or less, and even more preferably equal to about 310° C. or less. The melt temperature of the composition may be from about 290° C. to about 320° C., as measured according to ISO 11357, section 3.

[0088] The composition may comprise one or more other polymers not belonging to the family of PAEKs, especially other thermoplastic polymers.

[0089] The composition may also comprise additives and/or fillers.

The fillers may in particular be reinforcing fillers, including mineral fillers such as carbon black, carbon or non-carbon nanotubes, crushed or non-crushed fibers (glass, carbon). The composition comprising PAEK(s) may comprise less than about 50% by weight of filler, and preferably less than 40% by weight of filler relative to the total weight of composition.

[0090] The additives may in particular be stabilizing agents (light, in particular UV, and heat such as phosphates), optical brighteners, dyes, pigments, energy-absorbing additives (including UV absorbers), melt viscosity-controlling agents, crystallization rate-controlling agents or a combination of these additives. The composition may comprise less than 10%, preferably less than 5%, and more preferably less than 1% by weight of additives.

[0091] The composition is suitable for being printed in an extrusion (for example, fused filament fabrication) style 3D printer, with or without filaments.

[0092] The composition may be in the form of filaments or pellets, generally formed by extrusion, or may be in the form of powder or flakes.

[0093] In particular, the composition may be in the form of a filament comprising it, preferably made essentially of it and more preferably made of it. All possible limitations of the composition comprising at least one poly-aryl-ether-ketone (PAEK) described above may be applied to the filament comprising the at least one poly-aryl-ether-ketone as such.

[0094] For fused filament fabrication, the filaments may be of any size diameter, including diameters from about 0.6 to about 3mm, preferably diameters from about 1.7 to about 2.9 mm, more preferably diameters from about 1.7 mm to about 2.8 mm, as measured with an unweighted caliper.

Additive Manufacturing Process by Extrusion

[0095] A device useful for an additive manufacturing process by extrusion generally comprises all or some of the following components: [0096] (1) consumable material in the ready to print form (filament, pellets, powder, flakes, or polymer solution as specified by the printer); [0097] (2) a device feeding the material to the print head; [0098] (3) one or more print heads with a nozzle that can be heated up or cooled to a specified temperature for extruding of the melted material; [0099] (4) a print bed or substrate which may or may not be heated, where the part is being built/printed; and [0100] (5) a build environment surrounding the print bed and the object being printed which may or may not be heated or which may or may not be temperature controlled. The build environment may either be fully or partially enclosed forming a chamber, or open to the environment.

[0101] Generally, the extrusion printing process comprises one or more of the following steps: [0102] (1) feeding the composition comprising PAEKs in the form of filament, pellets, powder, flakes, or polymer solution into a 3D printer, the parts of which may or may not be heated to one or more predetermined temperatures; [0103] (2) setting the computer controls of the printer to provide a set volume flow of material, and to space the printed lines at a certain spacing; [0104] (3) feeding the composition to a heated nozzle at an appropriate set speed which may be pre-determined; and [0105] (4) moving the nozzle into the proper position for depositing a set or predetermined amount of composition; and [0106] (5) optionally adjusting the temperature of the build environment.

[0107] The extrusion melting process of the invention is carried out at an extrusion temperature equal to 330° C. or less. In particular, the extrusion temperature may be equal to about 325° C. or less, preferentially equal to about 320° C. or less. For compositions comprising PAEKs as the one used in the invention, the extrusion temperature is generally not less than about 300° C., preferably not less than 300° C. The feed into the printer has a melt viscosity from 200 to 1500 Pa.Math.s, according to ASTM D3835-16, as measured at a temperature of 320° C. and at a shear rate of 100 s.sup.−1, by capillary rheology using a 1 mm diameter, 15 mm long die. For these ranges of melt viscosities, it may be possible to operate the process at room temperature, i.e. with no heated print bed and/or no heated build environment.

[0108] Advantageously, the print bed may be heated to a temperature: [0109] from about Tg−60° C. to about Tg+5° C.; [0110] preferably from about Tg−30° C. to about Tg; [0111] and even more preferably from about Tg−20° C. to about Tg−5° C.;
wherein Tg is the glass transition temperature of the composition.
For a composition essentially consisting of, preferentially consisting of PEKK having a T:T+I ratio of 60%, Tg is around 160° C., meaning that the print bed temperature may be chosen from about 100° C. to about 165° C., or from about 130° C. to about 160° C., or from about 140° C. to about 155° C. This enables to promote adhesion of the first extruded layer on the print bed and to minimize the effects of contraction upon cooling since the first layer can be maintained at a high temperature for the entire build process.

[0112] The build environment may be actively or passively heated. An actively heated build environment has supplemental heating elements and controls beyond the heated bed that control the air temperature inside the build environment. A passively heated chamber has no controls, but uses the heat from the heated print bed and the nozzle(s) to increase the air temperature in the build environment. Advantageously, the build environment is passively heated, as the temperature of the build environment during the process may not exceed 85° C., or preferably may not exceed 70° C., or even more preferably may not exceed 60° C.

[0113] The process may take place in air, or under an inert gas such as nitrogen, if the printer makes it possible to control the composition of the gas within the build environment.

[0114] The process may take place at atmospheric pressure or at pressures below if the printer makes it possible to control the pressure within the build environment. Generally, “desktop printers” only allow to print at atmospheric pressure.

[0115] The 3-D printer may be programmed to operate at about 105 to about 130% overflow in order to reduce the internal void content, and improve overall part quality. This means that the volume of thermoplastic polymer composition fed by the printer is higher than the calculated volume required for the 3-D article being formed. Overflow may be controlled to result in a denser and mechanically stronger part. Overflow also helps to compensate for shrinkage, while increasing the strength and mechanical properties of the printed article. The overflow may be set by at least two different methods. In the first method, the software/printer is set to feed a higher percent of material into the nozzle than would be normally needed. In the second method, the software/printer may be set to decrease the spacing between lines, and thus create an overlap in the lines, resulting in extra material being used to print the article.

[0116] Process parameters of the 3-D printer may be adjusted to minimize shrinkage and warping, and to produce 3-D printed parts having optimum strength and elongation. The use of selected process parameters applies to any extrusion/melt 3D printer, and preferably to filament printing (e.g. FFF).

[0117] The print (head) speed may be between about 6 to about 200 mm/sec.

[0118] The thickness of each print layer may be from about 0.10mm to about 4 mm.

[0119] The process may also comprise a post-crystallization step of the printed part in order to increase the crystallinity of the printed part to a desired level by heating it at a temperature over the glass transition temperature of the composition for a certain amount of time.

[0120] An advantage of the present invention is the ability to print dimensionally stable (low warping) items using simple and low cost equipment, commonly called “desktop printers”. These printers operating at “low” extrusion temperature and at “low” build environment temperature do not require special high powered heater or specifically designed thermal isolation. Most typically the temperature control system for the extrusion nozzle on these systems uses a thermistor to measure temperature. Thermistors used on this type of printer are typically selected to be most accurate from about 150° C. to 250° C. and above 330° they are not accurate enough for reliable temperature measurements. The electrical heaters used in these printers may also not be powerful enough to maintain a nozzle temperature high enough to process many typical high performance thermoplastics. Moreover, the build chamber temperature does not require sophisticated design, materials, and heat management systems, lowering overall printer cost. Printers as the one used to print polylactic acid and/or acrylonitrile butadiene styrene may generally be suitable to carry out the process of the invention provided their nozzle can reach the suitable extrusion temperature. As a matter of fact, these desktop printers may come equipped with nozzles capable of reaching temperatures in excess of 300° C., which may even reach the temperature required in the additive manufacturing process of the invention. In that case, no upgrade of the nozzle is required. For printers with extrusion heads only capable of reaching temperatures below that required for the process of the invention, there are a number of commonly available aftermarket upgrade kits compatible with most printers.

[0121] A non-exhaustive list of suitable desktop printers which may be used in the process of the invention are : “Ultimaker 2+” and “Ultimaker S5”, commercialized by Ultimaker BV; “MakerBot Replicator+”, commercialized by MakerBot Industries; “FlashForge Creator Pro 2017” commercialized by FlashForge Corporation; “LulzBot Mini” and “LulzBot Taz 6”, commercialized by Aleph Obbects Inc. and “PRUSA I3 MK2S”, commercialized by Prusa Research.

Experimental Data

[0122] Filaments, having a 2.85 mm diameter, and made of PEKK copolymers with a 60:40 T:I having different melt viscosities, according to ASTM D3835-16, measured at a temperature of 320° C. and at a shear rate of 100 5.sup.−1, by capillary rheology using a 1 mm diameter, 15 mm long die, were used. ASTM D638 tensile specimens of type IV were printed in the horizontal (XY-axis) and vertical orientations (Z-axis) using a “FUNMAT HT” commercialized by the company INTAMSYS. The printer was equipped with an enclosed chamber, active heating, and a high temperature nozzle. However, for the experiment, the chamber access panels were left open and the chamber heater disabled. The nozzle temperature was set to 320° C. and the print speed was fixed at 20 mm/sec.

[0123] In example 1, a PEKK having an inherent viscosity of 1.05 dL/g, as measured according to ISO 307 in an aqueous solution of 96% by weight sulfuric acid at 25° C., was used. The melt viscosity of the filament thereof was approximately 2000 Pa.Math.s.

[0124] In example 2, a PEKK having an inherent viscosity of 0.8 dL/g, as measured according to ISO 307 in an aqueous solution of 96% by weight sulfuric acid at 25° C., was used. The melt viscosity of the filament thereof was approximately 1700 Pa.Math.s.

[0125] In example 3, a PEKK having an inherent viscosity of 0.7 dL/g, as measured according to ISO 307 in an aqueous solution of 96% by weight sulfuric acid at 25° C., was used. The melt viscosity of the filament thereof was approximately 580 Pa.Math.s.

[0126] It was not possible to use the filament of example 1 to print at 320° C. due its too high viscosity at 320° C. The test was considered a failure. Example 1 is not according to the invention.

[0127] The filaments of example 2 and example 3 were successfully extruded. Tensile testing data for the specimens type IV according to ASTM D638 are shown in Table 1 below:

TABLE-US-00001 TABLE 1 Tensile Max Stress Strain at Strain at modulus (MPa) (MPa) yield (%) break (%) Example X/Y 3000 86 5.80 8.7 2 Z 3600 31 N/A 1.0 Example X/Y 2800 88.5 6.25 64.1 3 Z 2700 41 N/A 1.6

[0128] The specimen of example 2, not according to the invention, showed some signs of warping visible to the naked eye as the surface of the specimen did not appear to be completely flat. On the contrary, the specimen of example 3, according to the invention did not show any sign of warping to the naked eye as the surface of the specimen appeared to be completely flat. As can be seen from the tensile data from table 1, the specimen from example 3 has better mechanical properties than the one of example 2 along X/Y directions or Z direction as indicated by the higher values of maximum stress, strain at yield and strain at break.

[0129] The PEKK copolymer with a 60:40 T:I ratio, as the one presently used is particularly advantageous, as it has: a melt temperature of around 305° C., a half-time crystallization of around 10 minutes at 215° C. and a coefficient of linear thermal expansion between −100° C. and the glass transition temperature of the composition of 2.65.10.sup.−5 K.sup.−1. This low coefficient of linear thermal expansion enables to substantially mitigate any warping of the part under construction even though the build environment is not actively heated.

[0130] Filaments of pure PEEK can not be used in the process of the claimed invention as they have a melting temperature of around 343° C. and cannot be extruded at a temperature equal to 330° C. or less. However, filaments made of a composition containing PEEK and having the properties as claimed herein may be used in the process according to the invention. It is however thought that compositions containing PEEK would be more prone to warping than PEKK copolymer with a 60:40 T:I ratio, as PEEK has a higher coefficient of linear thermal expansion, measured according to ISO 11359-2, as it is equal to around: 4.5.10-5K.sup.−1.