Fused filament printing

Abstract

The invention relates to a method for forming a three-dimensional object by fused filament fabrication comprising the step of selectively dispensing a polymer composition containing a semi-crystalline copolyamide in accordance with the shape of a portion of a three-dimensional object, characterized that the semi-crystalline copolyamide comprises: a) At least 70 wt. % of aliphatic monomeric units derived from i. Aminoacid A, or ii. diamine B and diacid C, and b) At least 0.5 wt. % of further monomeric units derived from a cyclic monomer, wherein wt. % is with respect to the total weight of the semi-crystalline copolyamide. The invention relates also relates to objects attainable by this method and to the use of the said semi-crystalline copolyamide in fused filament fabrication.

Claims

1. A method for forming a three-dimensional object by fused filament fabrication comprising the step of selectively dispensing a polymer composition containing a semi-crystalline copolyamide in accordance with the shape of a portion of a three-dimensional object, wherein the semi-crystalline copolyamide comprises: a) at least 70 wt. % of aliphatic monomeric units derived from i. aminoacid A, or ii. diamine B and diacid C, and b) at least 0.5 wt. % of further monomeric units derived from a cyclic monomer, wherein the weight percentage (wt. %) is with respect to the total weight of the semi-crystalline copolyamide.

2. The method according to claim 1, wherein the polymer composition comprises at least 30 wt. % of the semi-crystalline copolyamide, wherein wt. % is with respect to the total weight of the polymer composition.

3. The method according to claim 1, wherein the aliphatic monomeric units are derived from a monomer selected from the group consisting of epsilon-caprolactam, 1,4-diaminobutane and 1,10-decanedioic acid, 1,6-diaminohexane and 1,6-hexanedioic acid.

4. The method according to claim 1, wherein the cyclic monomer is an aromatic monomer, or a cycloaliphatic monomer, or a combination thereof.

5. The method according to claim 1, wherein the cyclic monomer is selected from the group consisting of isophoronediamine (IPD), cis-1,4-cyclohexanedicarboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, cis-1,3-cyclohexanedicarboxylic acid and trans-1,3-cyclohexanedicarboxylic acid.

6. The method according to claim 1, wherein the aliphatic monomeric units derived from A, or B and C, are selected from the group of monomers consisting of epsilon caprolactam, 1,4-diaminobutane and 1,10-decanedioic acid, 1,6-diaminohexane and 1,6-hexanedioic acid and the further monomeric units derived from a cyclic monomer are selected from the group of monomers consisting of isophoronediamine (IPD), cis-1,4-diaminocyclohexane, trans-1,4-diaminocyclohexane, bis-(p-aminocyclohexane)methane (PACM), 2,2-Di-(4-aminocyclohexyl)-propane, 3,3′-dimethyl-4-4′-diaminodicyclohexylmethane (DMDC), p-xylylenediamine, m-xylylenediamine, 3,6-bis(aminomethyl)norbornane, isophthalic acid (I), terephthalic acid (T), 4-methylisophthalic acid, 4-tert-butylisophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, cis-1,4-cyclohexanedicarboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, cis-1,3-cyclohexanedicarboxylic acid and trans-1,3-cyclohexanedicarboxylic acid.

7. The method according to claim 1, wherein the printing speed is at least 10 mm/s.

8. The method according to claim 1, wherein the further monomeric units derived from a cyclic monomer comprise isophorone diamine and terephthalic acid.

9. The method according to claim 1, wherein the filament is supplied from a coil.

10. The method according to claim 1, wherein the filament is produced by melt-extrusion of a granulate material comprising the polymer composition.

11. The method according to claim 1, wherein aminoacid A comprises epsilon-caprolactam, aminodecanoic acid, aminoundecanoic acid, or aminododecanoic acid.

12. The method according to claim 11, wherein diamine B comprises 1,4-diaminobutane, 1,5-diaminopentane, or 1,6-diaminohexane.

13. The method according to claim 12, wherein diacid C comprises 1,6-hexanedioic acid, 1,8-octanedioic acid, 1,9-nonanedioic acid, 1,10-decanedioic acid, 1,11-undecanedioic acid, 1,12-dodecanedioic acid, 1,13-tridecanedioic acid, 1,14-tetradecanedioic acid, 1,15-pentadecanedioic acid, 1,16-hexadecanedioic acid, 1,17-heptadecanedioic acid, or 1,18-octadecanedioic acid.

14. The method of claim 13, wherein the cyclic monomer comprises isophoronediamine (IPD), cis-1,4-diaminocyclohexane, trans-1,4-diaminocyclohexane, bis-(p-aminocyclohexane)methane (PACM), 2,2-Di-(4-aminocyclohexyl)-propane, 3,3′-dimethyl-4-4′-diaminodicyclohexylmethane (DMDC), p-xylylenediamine, m-xylylenediamine, 3,6-bis(aminomethyl)norbornane, isophthalic acid (I), terephthalic acid (T), 4-methylisophthalic acid, 4-tert-butylisophthalic acid, 1,4-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid, ¬cis-1,4-cyclohexanedicarboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, cis-1,3-cyclohexanedicarboxylic acid, or trans-1,3-cyclohexanedicarboxylic acid.

15. The method of claim 14, wherein the semi-crystalline copolyamide comprises between 0.8 to 7 wt. % of further monomeric units derived from at least two different cyclic monomers.

16. The method of claim 1, wherein the semi-crystalline copolyamide comprises at least 80 wt. % of aliphatic monomeric units derived from i. aminoacid A, or ii. diamine B and diacid C; and between 0.8 to 3 wt. % of further monomeric units derived from a cyclic monomer.

17. The method of claim 16, wherein the polymer composition comprises at least 60 wt. % of the semi-crystalline polyamide, relative to the total weight of the polymer composition.

18. The method of claim 1, wherein the polymer composition consists of the semi-crystalline copolyamide.

Description

(1) FIG. 1 shows a schematic view of an example of a print head of an FFF apparatus that may be used in the method according to the invention and a substrate.

(2) FIG. 2 shows a printed test specimen.

(3) FIG. 3 shows the single perimeter object and location of test specimen.

(4) FIG. 1 shows a schematic view of an example of a print head of an FFF apparatus that may be used in the method according to the invention. A filament (1) is transported from a reel (not shown) by a pair of wheels (2) into an oven (3) of the print head, for melting the filament. The molten material of the filament flows through de nozzle (4). Pressure to obtain this flow is obtained by force applied by the pair of wheels to the filament and yet un-molten filament acting as a piston in the first part of the oven. The extrudate (5) leaving the nozzle is deposited on the substrate (6), respectively the object being formed, positioned below the nozzle.

(5) FIG. 2 shows a test specimen for determining the strain at break (4).

(6) FIG. 3 shows the schematic representation of a pentagonic shaped printed single perimeter object (1) consisting of just one track (perimeter) deposited in the height direction on top of each other as depicted schematically by the dotted lines (3). The tensile test specimens (2) are located in each section of the pentagonic shape. They are punched out of the prints prior to determination of the tensile properties.

EXPERIMENTS

(7) Materials Used:

(8) PA12; product data from datasheet in Stratasys FDM Nylon 12™ (Eden Priairie, US)

(9) PA-6 homopolymer; viscosity number of 220.

(10) PA-6 copolymer: PA-6/IPDT, in which 1 wt. % IPDT is present; viscosity number of 220.

(11) PA-6I/6T; amorphous copolyamide in which I/T is 7/3; viscosity number 40.

(12) PA-6/66 copolymer

Comparative Experiment A

(13) For PA12, the values in the datasheet of Stratasys FDM Nylon 12™ (Eden Priairie, US) were used. Herein test bars were prepared by printing in a horizontal plane (XY), where X is coinciding with the length direction, Y the thickness direction and Z the width direction of the test bars respectively, often named “on-edge” (ZX) orientation. Tensile properties were measured in XZ-direction, i.e. testing direction is in printing direction. The data are listed in Table 1.

Comparative Experiment B

(14) A filament of PA-6 homopolymer having a diameter of 1.75 mm was printed into tensile test specimens of type ISO527BA with a Cartesio 3D-printer manufactured by MaukCC, Maastricht, The Netherlands. A schematic view of such a printer is shown in FIG. 1. The temperature of the oven was 260° C., the diameter of the nozzle was 0.4 mm and the substrate temperature 80° C. The extrudate leaving the nozzle was deposited in a layer by layer way on the substrate where the tracks has an alternating 45°/−45° angle relative to the testing direction, leaving a pattern as shown in FIG. 2.

(15) After conditioning at ambient conditions (23° C., 50% rel. humidity) for at least 3 days, the mechanical properties, Young's modulus, stress at break and elongation at break are determined in a tensile tester using a cross-head speed of 50 m/min according to ISO527. The results (average of 3 specimens) are summarized in Table 1.

Comparative Experiment C

(16) As comparative Experiment B, but now a blend of 80/20 wt/wt. % of PA6 homopolymer and PA-6I/6T was extruded into filament of 1.75 mm diameter and printed into tensile test specimens using the same conditions. The results (average of 3 specimens) are summarized in Table 1.

Example 1

(17) As comparative Experiment B, but now a PA-6/IPDT copolymer was used, in which 1 wt. % of IPDT is present. The results (average of 3 specimens) are summarized in Table 1.

(18) TABLE-US-00001 TABLE 1 mechanical data Stress Strain Modulus at break at break [MPa] [MPa] [%] Comp. PA12 1282 46.0 30 Experiment A Comp. PA-6 2159 ± 121 60.8 ± 2.0 13.5 ± 3.6 Experiment B Comp. Blend of PA-6 2089 ± 319 56.5 ± 2.3  2.9 ± 0.3 Experiment C and PA-6I/6T Example I PA-6/IPDT 1940 ± 333 56.0 ± 5.4 10.9 ± 8.5

(19) The results in Table 1 show that the copolymer of Example I has better mechanical properties than PA12 in Comparative Experiment A. In comparison with PA12, the copolymer has a significant higher tensile properties for the modulus and stress at break. The modulus and stress at break of the copolymer of Example I are comparable to the homopolymer of Comparative Experiment B and the blend of Comparative Experiment C, while the strain at break of Example I is comparable to the homopolymer of Comparative Experiment B and much better as compared to the blend Comparative Experiment C.

(20) Single Perimeter Objects, Tested in z-Direction (ISO 527 1BA), Printed at a Temperature of Tm+40° C.

Example II

(21) Single perimeter objects with extended pentagon shape were prepared by printing copolymer PA-6/IPDT at various printing speeds ranging from 10 to 50 mm/s. A filament of copolymer having a diameter of 1.75 mm was printed with a Cartesio 3D-printer manufactured by MaukCC, Maastricht, The Netherlands. The temperature of the oven was 260° C., the diameter of the nozzle was 0.4 mm and the substrate temperature 80° C. The extrudate leaving the nozzle was deposited in a layer by layer way on the substrate, growing the object in vertical direction (z-axis). Small tensile bars (ISO 527 1 BA) were punched out the printed objects in the length direction (z-axis). Thus tensile tests were performed in z-direction perpendicular to the printing direction. The results are shown in Table 2.

Comparative Experiment D

(22) Example II was repeated except that instead of PA-6/IPDT, the PA-6 homopolymer was used. The melt temperature was set at 260° C. The results are shown in Table 2.

Comparative Experiment E

(23) Example II was repeated except that instead of PA-6/IPDT, a PA-6/66 copolymer was used. The melt temperature was set at 240° C. Printing at lower speed went OK, at higher speed was problematic. At a speed of 40 mm/s or higher the melt layers were not deposited consistently on top of each other. Raising the temperature gave some improvement, but the printed layer started to flow before the next layer was deposited. So, tensile data at these speeds could not be determined. The qualitative good products (up to 30 mm/s) were tested. The results are shown in Table 2.

(24) TABLE-US-00002 TABLE 2 Results of mechanical tests for Example II and Comparative Experiments D and E and different printing speeds 10 mm/s 20 mm/s 30 mm/s 40 mm/s 50 mm/s EX-II TM [MPa] 1573 ± 73  1751 ± 54  1834 ± 33  1905 ± 51  1793 ± 74  TS max[MPa] 41.5 ± 0.8  44.9 ± 0.9 44.9 ± 1.1 44.3 ± 1.5  41.4 ± 1.1  EaB [%] 7.2 ± 2.0  9.9 ± 3.9  8.5 ± 1.8 5.7 ± 1.3 4.7 ± 0.9 EaY [%] 3.6 ± 0.2  3.6 ± 0.2  3.8 ± 0.0 3.3 ± 0.1 3.3 ± 0.1 CE-D TM [MPa] 921 ± 186 1183 ± 120 1283 ± 113 1272 ± 64  1724 ± 59  TS max[MPa] 21.6 ± 12.sup.  37.5 ± 1.7 37.2 ± 2.3 34.1 ± 0.7  21.7 ± 12.sup.  EaB [%] 5.3 ± 7.7  3.9 ± 0.8  6.3 ± 1.7 4.8 ± 0.6 1.0 ± 0.8 EaY [%] n.a. n.a. n.a. n.a. n.a. CE-E TM [MPa] 1250 ± 81  1555 ± 175 1511 ± 116 n.a. n.a. TS max[MPa] 29.8 ± 1.7  43.8 ± 0.8 34.4 ± 9.7 n.a. n.a. EaB [%] 3.4 ± 1.6  4.9 ± 0.1  2.9 ± 1.4 n.a. n.a. EaY [%] n.a. n.a. n.a. n.a. n.a.

(25) It was expected that at low speeds, where it takes longer before the next layer is deposited and the printed layer would cool down more, as a consequence, the fusion would be less complete than at faster speed resulting in shorter time and higher temperature. At the same time, however, the temperature of the melt leaving the nozzle at lower speeds is higher and more homogeneous than at higher speed. Therefore, there was also expected to observe an optimum in the processing in terms of speed for each of the materials.

(26) As a surprise the copolymer in Example II showed a very good performance over the whole speed range. All test bars of the resulting products showed a yielding behavior and Tensile Modulus and Tensile Strength are high at all speeds applied. Elongation at break is high as well, only somewhat lower at the highest speed.

(27) The homopolymer in Comparative Experiment D showed a brittle failure behavior with a much lower Tensile Modulus and Tensile Strength at 10 to 40 mm/sec, compared to Example II, and at 50 mm/s the Tensile Modulus is as high as that of Example II, but Tensile Strength and Elongation at break are much lower.

(28) The PA-6/66 copolymer of Comparative Experiment E could not be processed at 40 and 50 mm/s. Furthermore, at 10 to 30 mm/s, the copolymer of Comparative Experiment E showed a brittle failure behavior with a much lower Tensile Modulus, Tensile and Elongation at Break, compared to Example II.

(29) Thus printing while employing PA-6/IPDT (Example II) allowed a broader processing window and resulted in products with better mechanical properties and less warpage or curling is to be expected as compared to Comparative Experiment D and E.