Composite material for 3D printing and method for its preparation

Abstract

The application relates to the technical field of nylon powder composite materials, and discloses a composite material for 3D printing and a preparation method thereof, the composite material comprising nylon powder and an additive, the porosity of the nylon powder being 10%-50% as measured by a mercury injection method according to ISO 15901-1, the particle size span being 0.7-1.2 as measured by a laser diffraction method according to ISO 13320, and the median particle size D50 being 10-100 mu m; and the additive comprising one or more of antioxidants, powder flow aids, melt leveling agents, phosphorus-based additives and toner powder. The composite material of the application can ensure that the fusing ink is fully absorbed, while the powder maintains good loftiness and fluidity, significantly improves the stability of the printing process, widens the printing temperature interval, improves the sintering forming effect, and makes the surface of the workpiece smoother by reasonably regulating the porosity, particle size span and median particle size of the nylon powder and compounding the corresponding additive.

Description

Technical Field

[0001] This application relates to the field of nylon powder composite materials technology, specifically to a composite material for 3D printing and its preparation method. Background Technology

[0002] Multi-jet melting technology is a highly efficient powder bed fusion 3D printing technology. Its working principle is as follows: powder material is laid layer by layer in the forming cylinder, and a bonding agent and refining agent are selectively sprayed onto the powder surface through the nozzle. Then, a heating source with a fixed wavelength is used to heat the powder layer as a whole, so that the powder in the target area is selectively sintered, and finally the layers are stacked to form a three-dimensional workpiece. In practical applications of multi-jet melting technology, nylon powder has become the most widely used material due to its excellent mechanical properties and process adaptability. However, existing nylon powders generally have significant shortcomings: affected by factors such as particle size distribution and flowability, printed workpieces have a strong grainy texture and poor surface precision, making it difficult to meet the needs of high-end applications; at the same time, unreasonable powder surface characteristics and pore structure lead to poor ink absorption performance, uneven absorption and insufficient wetting of bonding agents and refining agents, directly affecting sintering uniformity and the mechanical properties of the molded parts; in addition, in the high-temperature and oxygen-rich environment of the printing process, the powder is prone to thermal oxidative degradation, which not only produces obvious color differences but also causes its own performance to deteriorate, reducing the consistency of product appearance and the efficiency of powder reuse. Summary of the Invention

[0003] This application provides a composite material for 3D printing and its preparation method to solve the problems of insufficient surface precision and significant particle texture of nylon powder used in 3D printing, uneven ink absorption and insufficient wetting of fusion binder and refiner leading to poor sintering consistency and mechanical properties, and easy thermal oxidation degradation, obvious color difference and performance deterioration in high temperature and oxygen-containing printing environment, which in turn affects the product appearance consistency and powder reuse efficiency.

[0004] In a first aspect, this application provides a composite material for 3D printing, comprising nylon powder and additives, wherein the porosity of the nylon powder is 10%-50% as determined by mercury porosimetry according to ISO 15901-1, the particle size range is 0.7-1.2 as determined by laser diffraction according to ISO 13320, and the median particle size D50 is 10 μm-100 μm; The additives include one or more of the following: antioxidants, powder flow aids, melt leveling agents, phosphorus-based additives, and color powders.

[0005] This application provides a composite material for 3D printing, comprising nylon powder and additives. Using mercury porosimetry under a maximum test pressure of 30,000 psi, the porosity of the nylon powder was determined to be 10%-50%. Using laser diffraction under a light-blocking condition of 10%-15%, the particle size range was determined to be 0.7-1.2, and the median particle size D50 was 10 μm-100 μm. The particle size span is calculated according to the following formula: Particle size span = (D90 - D10) / D50 Wherein, D50 represents the particle size corresponding to a cumulative volume distribution of 50%, i.e., the median particle size; D10 represents the particle size corresponding to a cumulative volume distribution of 10%; and D90 represents the particle size corresponding to a cumulative volume distribution of 90%.

[0006] The composite material for 3D printing provided in this application achieves a balance between ink absorption performance, powder spreading performance, and sintering stability by controlling the porosity, particle size distribution, and median particle size D50 of the nylon powder within suitable ranges. Suitable porosity facilitates the penetration of fused ink into the nylon powder and its full absorption, preventing insufficient pore structure that hinders ink penetration and avoiding excessive porosity that leads to loose powder and reduced spreading stability. Suitable particle size distribution and median particle size D50 promote the formation of a uniform and stable powder bed, reducing scratching and graininess on the printed surface caused by coarse particles, while preventing powder agglomeration due to a narrow particle size distribution. This improves the powder spreading uniformity and forming stability during multi-jet fusion 3D printing.

[0007] This application improves the overall printability of composite materials by compounding antioxidants, powder flow aids, melt leveling agents, phosphorus-based additives, and pigments into nylon powder. Specifically, antioxidants and phosphorus-based additives enhance the thermo-oxidative stability of nylon powder in high-temperature, oxygen-rich printing environments, mitigating yellowing and performance degradation. Powder flow aids improve the flow and dispersion of powder particles, increasing powder uniformity. Melt leveling agents improve the melt-spreading state of nylon powder during sintering, widening the printable temperature window and reducing surface graininess. Pigments can be used to adjust the color of the composite material and the appearance of the printed parts.

[0008] The composite material of this application can maintain good powder flowability and molding stability while ensuring full ink absorption, thereby improving the stability of the printing process, the surface quality of printed parts, and the appearance consistency during material reuse.

[0009] In one optional embodiment, the composite material comprises 100 parts nylon powder, 0-2 parts antioxidant, 0-1 part powder flow aid, 0.1-1 part melt leveling agent, 0.1-2 parts phosphorus-based additive, and 0-2 parts color powder, based on 100 parts by weight of the nylon powder.

[0010] Optionally, based on 100 parts by weight of the nylon powder, the composite material includes 100 parts of nylon powder, 0.2-2 parts of antioxidant, 0.5-1 parts of powder flow aid, 0.5-1 parts of melt leveling agent, 0.5-2 parts of phosphorus-based additive, and 1-2 parts of color powder.

[0011] Optionally, based on 100 parts by weight of the nylon powder, the composite material includes 100 parts of nylon powder, 1-2 parts of antioxidant, 0.5-1 parts of powder flow aid, 0.5-1 parts of melt leveling agent, 0.5-2 parts of phosphorus-based additive, and 1-2 parts of color powder.

[0012] In one optional embodiment, the nylon powder is a long-chain aliphatic polyamide powder, wherein the number of carbon atoms in its monomer is 10-15, preferably 10-12.

[0013] In one alternative embodiment, the nylon powder includes one or more of nylon 1010 (chemical name: polydecanoyl decanoyl diamine), nylon 1012 (chemical name: polydodecanoyl decanoyl diamine), nylon 11 (chemical name: polyundecanoamide), and nylon 12 (chemical name: polydodecanolactam).

[0014] In one optional embodiment, the phosphorus-based auxiliaries include one or more of phosphoric acid, phosphorous acid, and sodium hypophosphite.

[0015] In one alternative embodiment, the melt leveling agent comprises a modified siloxane compound.

[0016] In one alternative embodiment, the modified siloxane compound includes one or more of the following: polyether-modified siloxane compounds (e.g., Delco leveling agent 432 purchased from Innovent Chemicals), alkyl-modified siloxane compounds, and aralkyl-modified siloxane compounds.

[0017] In one optional embodiment, the polyether-modified siloxane compound includes one or more of Haichuan New Material leveling agent DSX-2000, Jiaming Chemical leveling agent CM-450, and Digo leveling agent 432.

[0018] In one optional embodiment, the powder flow aid includes one or more of fumed silica, saponified metal salts, and alumina.

[0019] The saponified metal salt includes one or more of lithium stearate, calcium stearate, and zinc stearate.

[0020] In one optional embodiment, the antioxidant includes one or more of hindered amine antioxidants, cuprous iodide antioxidants, potassium iodide antioxidants, hindered phenolic antioxidants, phosphite antioxidants, and inorganic phosphate antioxidants. In one alternative embodiment, the pigment includes one or more of titanium dioxide, carbon black, antimony tin oxide, lanthanum hexafluoride, and basic copper sulfate.

[0021] Secondly, this application provides a method for preparing a composite material as described in any of the above technical solutions, characterized in that: the nylon powder and additives are prepared by mixing them using a high-speed mixer.

[0022] In one optional implementation, the mixing speed of the high-speed mixer is controlled to be 800 rpm-1200 rpm; And / or, control the mixing time to 3-6 minutes.

[0023] The preparation method of this application uses a high-speed mixer to mix nylon powder and additives, which can make antioxidants, powder flow aids, melt leveling agents, phosphorus-based additives, color powders and other additives more uniformly dispersed in the nylon powder system, thereby improving the consistency of the composite material composition and the stability during the printing process.

[0024] The technical solution of this application has the following advantages: The composite material of this application, through reasonable control of the porosity, particle size range, and median particle size of nylon powder, and the formulation of appropriate additives, can ensure the full absorption of fused ink while maintaining good powder bulkiness and flowability, significantly improving the stability of the printing process. Combined with the use of melt leveling agents, it can effectively widen the printing temperature range, improve the sintering effect, make the surface of the parts smoother, and greatly enhance the process adaptability and finished product quality of multi-jet fusion 3D printing. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a graph showing the change of powder B value over time for the composite materials prepared in Examples 4 to 6 of this application. Detailed Implementation The following embodiments are provided to better understand this application. However, the following embodiments do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining the features of this application with other prior art, falls within the scope of protection of this application.

[0027] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0028] The test methods involved in the embodiments and comparative examples of this application are as follows: Porosity test method: The porosity of the nylon powder sample to be tested was determined according to the mercury intrusion porosimetry method specified in ISO 15901-1. Take 1 g to 3 g of the nylon powder sample to be tested and dry it in an oven at 80℃ for 4 h, and weigh the mass of the dried sample with a weighing accuracy of 0.0001 g.

[0029] The weighed sample was placed into a dry dilatometer and connected to the low-pressure station port of the mercury porosimeter. The vacuum system was activated to degas the sample in the dilatometer for 60 minutes. After degassing, the dilatometer was brought into contact with mercury under vacuum conditions, allowing the mercury to enter the dilatometer and fill the voids around the sample under the influence of gravity and low pressure. The initial mercury volume V1 was recorded at this point.

[0030] The mercury pressure was then gradually increased. During the low-pressure test phase, the pressure was increased from atmospheric pressure to 40 psi, and the volume of mercury penetration into the sample was continuously recorded at different pressures. After the low-pressure test, the dilatometer was transferred to the high-pressure station of the mercury porosimeter. During the high-pressure test phase, the pressure was gradually increased to 30,000 psi, and the pressure-mercury penetration volume curve was continuously recorded during the high-pressure phase. After the test, the pressure was gradually reduced to atmospheric pressure, and the volume change of mercury exiting the sample pores and the corresponding pressure curve were recorded during the depressurization process.

[0031] The porosity of the nylon powder sample under test was calculated based on the mercury intrusion volume data obtained from the test. The calculation formula is as follows: Porosity = (Total pore volume / Apparent total volume) × 100%. Wherein, the total pore volume is the cumulative volume of mercury intruding into the sample pores during the test at the highest test pressure; the apparent total volume is the apparent volume occupied by the sample within the dilatometer, which can be calculated based on the effective volume of the dilatometer and the initial mercury filling volume. Each sample was tested in parallel at least twice, and the average value of the test results was taken as the porosity of the sample.

[0032] Median particle size and particle size span testing methods: The median particle size D50 and particle size span of the nylon powder sample to be tested were determined according to the laser diffraction method specified in ISO 13320. 3 g of the nylon powder sample to be tested was placed in 100 mL of ethanol and ultrasonically dispersed for 2 min to form a uniform powder suspension.

[0033] The dispersed powder suspension was added to the test cell of the laser particle size analyzer, and the test parameters were set according to the operating procedures of the laser particle size analyzer. During the test, the sample occlusion was controlled at 10%–15%, and the test was started after the occlusion stabilized. After the test, the laser particle size analyzer output a particle size distribution test report, obtaining the particle size distribution data of the tested nylon powder sample, including D10, D50, and D90. Among them, D50 represents the particle size corresponding to 50% of the cumulative volume distribution, i.e., the median particle size; D10 represents the particle size corresponding to 10% of the cumulative volume distribution; and D90 represents the particle size corresponding to 90% of the cumulative volume distribution.

[0034] The particle size span is calculated using the following formula: Particle size span = (D90 - D10) / D50. Each sample is tested in parallel three times, and the average of the three test results is taken as the median particle size D50 and particle size span of the sample.

[0035] The raw materials involved in the embodiments and comparative examples of this application are as follows: Nylon 11, Nylon 12, and Nylon 1012 were purchased from Wanhua Chemical. Phosphoric acid, purchased from Inocare Chemical Co., Ltd.; Sodium hypophosphite, purchased from Inokai Chemical Co., Ltd.; Phosphorous acid, purchased from Inokai Chemical Co., Ltd.; Antioxidant 168 was purchased from Inocare Chemical Co., Ltd. Antioxidant 1098 was purchased from Inokai Chemical Co., Ltd. Copper pyrophosphate, purchased from Inokai Chemical Co., Ltd. Cuprous iodide, purchased from Inocare Chemical Co., Ltd.; Potassium iodide, purchased from Inokai Chemical Co., Ltd.; Fumed silica, purchased from Inokai Chemical Co., Ltd.; Evonik alumina C, purchased from Inocare Chemical Co., Ltd.; Calcium stearate, purchased from Inocare Chemical Co., Ltd.; Zinc stearate, purchased from Inokai Chemical Co., Ltd.; Haichuan New Materials' leveling agent DSX-2000 was purchased from Inokai Chemical Co., Ltd. Garmin Chemical Leveling Agent CM-450, purchased from Inokai Chemical Co., Ltd. Tigo leveling agent 432, purchased from Inocare Chemical Co., Ltd.; Tin antimony oxide, purchased from Inokai Chemical Co., Ltd.; Titanium dioxide, purchased from Inokai Chemical Co., Ltd.; Carbon black, purchased from Inokai Chemical Co., Ltd.; Lanthanum hexafluoride, purchased from Inokai Chemical Co., Ltd.

[0036] Example 1 This embodiment provides a composite material for 3D printing, as detailed below: Weigh out 10 kg of nylon 12 powder, 50 g of antioxidant 168, 50 g of antioxidant 1098, 50 g of leveling agent DSX-2000, 50 g of phosphoric acid, and 50 g of fumed silica, and set aside.

[0037] The nylon 12 powder has a porosity of 30%, a particle size span of 0.93, and a median particle size D50 of 50 μm; the melt leveling agent is Haichuan New Material DSX-2000 leveling agent.

[0038] The nylon 12 powder, antioxidant 168, antioxidant 1098, leveling agent DSX-2000, phosphoric acid, and fumed silica were added to a high-speed mixer and mixed at 800 rpm for 6 minutes. After mixing, the mixture was discharged to obtain a composite material for 3D printing.

[0039] Based on 100 parts by weight of the nylon 12 powder, in this embodiment, the composite material includes 100 parts of nylon 12 powder, 1.0 part of antioxidant, 0.5 part of powder flow aid, 0.5 part of melt leveling agent, and 0.5 part of phosphorus-based additive.

[0040] Example 2 This embodiment provides a composite material for 3D printing, as detailed below: Weigh out 10 kg of nylon 11 powder, 200 g of copper pyrophosphate, 10 g of Garmin Chemical leveling agent CM-450, 10 g of sodium hypophosphite, and 200 g of antimony tin oxide, and set aside.

[0041] The nylon 11 powder has a porosity of 11%, a particle size span of 0.79, and a median particle size D50 of 10 μm; the melt leveling agent is Jiaming Chemical leveling agent CM-450.

[0042] The nylon 11 powder, copper pyrophosphate, leveling agent CM-450, sodium hypophosphite, and antimony tin oxide were added to a high-speed mixer and mixed at 1200 rpm for 3 minutes. After mixing, the mixture was discharged to obtain a composite material for 3D printing.

[0043] Based on 100 parts by weight of the nylon 11 powder, in this embodiment, the composite material includes 100 parts of nylon 11 powder, 2.0 parts of antioxidant, 0.1 parts of melt leveling agent, 0.1 parts of phosphorus-based additive, and 2.0 parts of color powder.

[0044] Example 3 This embodiment provides a composite material for 3D printing, as detailed below: Weigh out 10 kg of nylon 1012 powder, 100 g of cuprous iodide, 100 g of potassium iodide, 100 g of Evonik alumina C, 100 g of DIGIC leveling agent 432, 100 g of phosphorous acid and 100 g of titanium dioxide, and set aside.

[0045] The nylon 1012 powder has a porosity of 45%, a particle size span of 1.05, and a median particle size D50 of 100 μm; the melt leveling agent is DIGIC leveling agent 432.

[0046] The nylon 1012 powder, cuprous iodide, potassium iodide, Evonik alumina C, DIGIC leveling agent 432, phosphorous acid, and titanium dioxide were added to a high-speed mixer and mixed at 1000 rpm for 5 minutes. After mixing, the mixture was discharged to obtain a composite material for 3D printing.

[0047] Based on 100 parts by weight of the nylon 1012 powder, in this embodiment, the composite material includes 100 parts of nylon 1012 powder, 2.0 parts of antioxidant, 1.0 part of powder flow aid, 1.0 part of melt leveling agent, 1.0 part of phosphorus-based additive, and 1.0 part of color powder.

[0048] Example 4 The only difference between this embodiment and Embodiment 1 is that the amount of phosphoric acid used is 10 g.

[0049] Based on 100 parts by weight of the nylon 12 powder, in this embodiment, the composite material includes 100 parts of nylon 12 powder, 1.0 part of antioxidant, 0.5 part of powder flow aid, 0.5 part of melt leveling agent, and 0.1 part of phosphorus-based additive.

[0050] Example 5 The only difference between this embodiment and Embodiment 1 is that the amount of phosphoric acid used is 100 g.

[0051] Based on 100 parts by weight of the nylon 12 powder, in this embodiment, the composite material includes 100 parts of nylon 12 powder, 1.0 part of antioxidant, 0.5 part of powder flow aid, 0.5 part of melt leveling agent, and 1.0 part of phosphorus-based additive.

[0052] Example 6 The only difference between this embodiment and Embodiment 1 is that the amount of phosphoric acid used is 200 g.

[0053] Based on 100 parts by weight of the nylon 12 powder, in this embodiment, the composite material includes 100 parts of nylon 12 powder, 1.0 part of antioxidant, 0.5 part of powder flow aid, 0.5 part of melt leveling agent, and 2.0 parts of phosphorus-based additives.

[0054] Example 7 The only difference between this embodiment and Embodiment 1 is that the amount of leveling agent DSX-2000 used is 10 g.

[0055] Based on 100 parts by weight of the nylon 12 powder, in this embodiment, the composite material includes 100 parts of nylon 12 powder, 1.0 part of antioxidant, 0.5 part of powder flow aid, 0.1 part of melt leveling agent, and 0.5 part of phosphorus-based additive.

[0056] Example 8 The only difference between this embodiment and Embodiment 1 is that the amount of leveling agent DSX-2000 used is 100 g.

[0057] Based on 100 parts by weight of the nylon 12 powder, in this embodiment, the composite material includes 100 parts of nylon 12 powder, 1.0 part of antioxidant, 0.5 part of powder flow aid, 1.0 part of melt leveling agent, and 0.5 part of phosphorus-based additive.

[0058] Example 9 This embodiment provides a composite material for 3D printing, as detailed below: Weigh out 10 kg of nylon 12 powder, 50 g of leveling agent DSX-2000, 50 g of phosphoric acid, 50 g of fumed silica and 200 g of carbon black, and set aside.

[0059] The nylon 12 powder has a porosity of 10%, a particle size span of 0.7, and a median particle size D50 of 10 μm; the melt leveling agent is Haichuan New Material DSX-2000 leveling agent.

[0060] The nylon 12 powder, leveling agent DSX-2000, phosphoric acid, fumed silica, and carbon black were added to a high-speed mixer and mixed at 800 rpm for 6 minutes. After mixing, the mixture was discharged to obtain a composite material for 3D printing.

[0061] Based on 100 parts by weight of the nylon 12 powder, in this embodiment, the composite material includes 100 parts of nylon 12 powder, 0.5 parts of powder flow aid, 0.5 parts of melt leveling agent, 0.5 parts of phosphorus-based additive, and 2.0 parts of color powder.

[0062] Example 10 This embodiment provides a composite material for 3D printing, as detailed below: Weigh out 10 kg of nylon 12 powder, 50 g of antioxidant 168, 50 g of antioxidant 1098, 50 g of calcium stearate, 50 g of leveling agent DSX-2000, 50 g of sodium hypophosphite, and 200 g of lanthanum hexafluoride, and set aside.

[0063] The nylon 12 powder has a porosity of 50%, a particle size span of 1.2, and a median particle size D50 of 100 μm; the melt leveling agent is Haichuan New Material DSX-2000 leveling agent.

[0064] The nylon 12 powder, antioxidant 168, antioxidant 1098, calcium stearate, leveling agent DSX-2000, sodium hypophosphite, and lanthanum hexafluoride were added to a high-speed mixer and mixed at 800 rpm for 6 minutes. After mixing, the mixture was discharged to obtain a composite material for 3D printing.

[0065] Based on 100 parts by weight of the nylon 12 powder, in this embodiment, the composite material includes 100 parts of nylon 12 powder, 1.0 part of antioxidant, 0.5 part of powder flow aid, 0.5 part of melt leveling agent, 0.5 part of phosphorus-based additive, and 2.0 part of color powder.

[0066] Comparative Example 1 The only difference between this comparative example and Example 1 is that the porosity of the nylon 12 powder is 5%.

[0067] Comparative Example 2 The only difference between this comparative example and Example 1 is that the porosity of the nylon 12 powder is 60%.

[0068] Comparative Example 3 The only difference between this comparative example and Example 1 is that the particle size range of the nylon 12 powder is 1.4.

[0069] Comparative Example 4 The only difference between this comparative example and Example 1 is that the particle size range of the nylon 12 powder is 0.6.

[0070] Test Example 1 This test example tests and compares the composite materials for 3D printing prepared in the embodiments and comparative examples of this application. The test methods are as follows; Powder B-value test: Take 100 g of the composite material to be tested and place it in an 80℃ oven for 2 hours. Pour the treated composite material powder into a cuvette, filling it to at least 2 / 3 of its volume. Gently tap the cuvette to allow the powder to naturally compact and expel air from the gaps between the powder particles, ensuring a smooth surface. Perform black and white calibration on the colorimeter according to its instruction manual. After calibration, place the cuvette containing the powder to be tested stably at the instrument's measuring port, start the test, obtain the Lab colorimetric value of the powder, and record the B-value. Each sample is tested in parallel three times, and the average of the three test results is taken as the powder B-value of that sample. The higher the B-value, the higher the degree of yellowing of the composite material powder.

[0071] Bulk density test: 100 g of the composite material to be tested was placed in an 80℃ oven for 2 h to dry. A standard funnel and a cylindrical receiving cup with a fixed volume of 100 cm³ were prepared for the test. The mass of the empty receiving cup was weighed and recorded before the test. The dried composite material to be tested was allowed to fall freely and slowly into the receiving cup through the standard funnel until the powder naturally accumulated and overflowed from the cup. Then, excess powder was gently scraped off along the edge of the receiving cup with a flat scraper until the powder surface was flush with the cup rim. Vibration or compaction of the powder in the receiving cup was avoided during the scraping process. The total mass of the receiving cup after it was filled with powder was weighed, and the net mass of the powder in the receiving cup was obtained by subtracting the mass of the empty receiving cup from the total mass. The bulk density was calculated according to the following formula: Bulk density = Net mass of powder / Volume of receiving cup. Each sample was tested in parallel 3 times, and the average of the 3 test results was taken as the bulk density of the sample. Bulk density can be used to characterize the packing state of composite powder under the test conditions and as a reference index for evaluating powder spreadability and flowability.

[0072] Ink absorption test: The composite material to be tested was added to the powder supply unit of the HP Multi-Jet Fusion (MJF) 3D printer. Printing tests were conducted under the same powder layer thickness, ink jet volume, powder bed preheating temperature, heating conditions, and printed sample model. By adjusting the volumetric printing speed of the equipment, the penetration, spreading, and retention of the liquid jetted onto the powder bed surface during the printing process were observed. The ink absorption performance of the composite powder was evaluated in conjunction with whether the printed part could be formed completely.

[0073] When the volumetric printing speed is greater than 4000 cm³ / h, the jet liquid can be quickly absorbed by the toner bed, with no obvious liquid retention, flow, or over-spreading on the toner bed surface, and the printed parts can be formed completely; this is evaluated as "easy to absorb". When the volumetric printing speed is between 2000 cm³ / h and 4000 cm³ / h, the jet liquid can be absorbed by the toner bed and printing can be completed, but at higher printing speeds, there are insufficient absorption, local retention, or uneven spreading; this is evaluated as "difficult to absorb". When the volumetric printing speed is less than 2000 cm³ / h, the jet liquid still cannot be effectively absorbed by the toner bed, with obvious liquid retention, abnormal spreading, or insufficient wetting, resulting in the inability of the printed parts to be formed completely; this is evaluated as "unabsorbable".

[0074] "Condensation Temperature - Initial Non-Warp Temperature" Test: The composite materials prepared in each embodiment and comparative example were added to the powder supply unit of a multi-jet fusion 3D printer. Printing tests were conducted under the same powder bed thickness, volumetric printing speed, inkjet volume, heating power, printed sample model, and other printing parameters, with only the powder bed preheating temperature being varied. During the test, the powder bed preheating temperature was gradually increased in a 1°C gradient, and test samples of the same size and shape were printed at each powder bed preheating temperature. The powder bed state and the formed state of the printed parts were observed and recorded.

[0075] The initial non-warping temperature refers to the lowest powder bed preheating temperature at which, under the same printing parameters, the test sample can be formed completely without any warping, curling, or detachment of the printed edge from the powder bed that would affect the forming quality. The caking temperature refers to the lowest powder bed preheating temperature at which, under the same printing parameters, the composite material powder in the non-inkjet areas begins to exhibit adhesion, agglomeration, or caking phenomena that would affect normal powder spreading or powder recovery.

[0076] The "caking temperature - initial non-warping temperature" in Table 1 refers to the difference between the caking temperature and the initial non-warping temperature. This difference is used to characterize the printable temperature window of the composite material. The larger the difference, the wider the range of powder bed preheating temperatures that the composite material can be used under the conditions that the printed part does not warp and the powder bed does not caking, that is, the better the adaptability of the composite material to the printing process.

[0077] Printed part roughness: The composite materials obtained in each embodiment and comparative example were printed into 3D printed strips of the same size and shape. After sandblasting, the surface of the 3D printed strips was rinsed with deionized water to remove dust, impurities and residual particles, and the strips were dried for later use.

[0078] The surface roughness of the printed sample was tested using a surface roughness measuring instrument. Before testing, the instrument was calibrated using a certified standard roughness sample block to ensure that the instrument's accuracy and measurement range met the testing requirements. The test was conducted according to the methods specified in ISO 4287 and ISO 4288, with the sampling length λc set to 0.8 mm and the evaluation length ln set to 4.0 mm. The 3D printed sample to be tested was stably fixed on a vibration-isolated platform to keep the surface horizontal and prevent movement or vibration during the test. During the test, the scanning direction was perpendicular to the main machining texture direction of the printed sample surface, and the stylus measuring force was set to 1 mN. After starting the test, the instrument probe performed a uniform linear scan along the set path, and the Rz value, characterizing the surface roughness of the printed part, was obtained after the scan was completed. Each sample was tested three times at different locations on the same surface, and the average of the three test results was taken as the surface roughness of the sample. A larger Rz value indicates a larger surface roughness of the printed part.

[0079] Printing Results: The composite materials prepared in each embodiment and comparative example were added to the powder supply unit of a multi-jet fusion 3D printer. Printing tests were conducted under the same conditions: equipment model, powder thickness, volumetric printing speed, inkjet volume, powder bed preheating temperature, heating power, printed sample model, and other printing parameters. During the tests, the spreading state of the composite powder, the absorption state of the binder and / or refiner, the powder bed stability, and the forming state of the printed parts were observed and recorded.

[0080] If the composite material powder can be continuously and uniformly spread during the printing process, the binder and / or refiner sprayed onto the powder bed surface can be effectively absorbed by the powder bed, and the printed part can be formed completely, then it is evaluated as "printable". If, during the printing process, the ink cannot be effectively absorbed by the powder bed, the powder cannot be continuously spread, the powder bed stability is poor, the formed area is scratched or damaged by coarse particles, or the powder in the unsprayed area is severely caking, resulting in the printed part not being formed completely, then it is evaluated as "printing failed".

[0081] For samples rated "printable", further records were made based on the printing process and the surface condition of the printed parts: when the powder spreads continuously and the powder bed is stable during printing, and the surface of the printed parts is smooth without obvious graininess, scratches, caking, or yellowing, it was recorded as "good surface condition"; when the powder spread is discontinuous or the powder layer is not uniform during printing, but the printed parts can still be formed completely, it was recorded as "poor powder flowability"; when the surface of the printed parts has obvious graininess, roughness, or local scratches, it was recorded as "rough surface"; when the printed parts or composite material powders show yellowing, the degree of yellowing was recorded as "severe thermo-oxidative yellowing" or "moderate thermo-oxidative yellowing" based on the powder b-value test results; when the printed parts and composite material powders do not show obvious yellowing and the powder b-value changes little, it was recorded as "good resistance to thermo-oxidative yellowing".

[0082] The test results are shown in Table 1 below; Table 1: Performance Test Results

[0083] (In the table, "--" indicates that the corresponding item was not tested.) Comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the porosity of nylon powder affects the ink absorption performance, powder packing state, and printing stability of the composite material. The nylon powder used in Example 1 of this application has a porosity of 30%, and the resulting composite material can balance ink absorption and powder flowability, forming a relatively stable powder-spreading state and sintering state during printing, resulting in a better surface condition of the printed parts.

[0084] In Comparative Example 1, the nylon powder used had a low porosity, resulting in insufficient internal pore structure. This hindered the penetration and absorption of fused ink into the powder, leading to ink absorption issues during printing and hindering effective molding. Comparative Example 2 used nylon powder with a high porosity. While this facilitated rapid ink entry into the powder pores, the overall powder structure was too loose, resulting in poor packing and flow properties. This hindered the formation of a uniform and stable powder bed, similarly affecting the continuity and molding stability of the printing process. Therefore, this application utilizes an appropriate nylon powder porosity to achieve a better balance between ink absorption performance and powder spreading and flow properties, thereby improving the process adaptability and printing stability of the composite material in multi-jet fusion 3D printing.

[0085] Comparing Example 1 with Comparative Examples 3 and 4, it can be seen that the particle size range of nylon powder affects the uniformity of powder spreading, sintering stability and surface quality of the printed parts of the composite material.

[0086] The nylon powder used in Example 1 has a suitable particle size range and a reasonable particle size distribution, enabling it to form a relatively uniform and stable powder bed during printing. It also balances powder spreadability and surface quality, resulting in a better surface finish on the printed parts. In Comparative Example 3, the nylon powder has a larger particle size range, indicating a wider particle size distribution. The proportion of coarse particles or the influence of large-diameter particles are more pronounced, which can easily lead to decreased powder layer uniformity during powder spreading and forming, and may scratch or damage the formed areas, resulting in poorer surface quality of the printed parts. In Comparative Example 4, the nylon powder has a smaller particle size range, indicating a narrower particle size distribution. During heating, the powder is prone to compaction, insufficient space for heat transfer and melting state adjustment, making it more susceptible to caking and affecting the stability of the printing process.

[0087] This application proposes a method to reasonably control the powder particle size range, which is beneficial for balancing powder spreading uniformity, powder bed stability, and sintering quality. A larger particle size range can easily reduce the surface quality of the printed parts due to the influence of coarse particles, while a smaller particle size range can increase the risk of powder caking. Controlling the nylon powder particle size range within a reasonable range is beneficial for improving the forming stability of the composite material and the surface quality of the printed parts during multi-jet fusion 3D printing.

[0088] Examples 1, 4, 5, and 6 of this application compare the effects of phosphorus-based additives on composite materials. (Refer to Table 1 and...) Figure 1 It is evident that, when the nylon powder, antioxidant, powder flow aid, melt leveling agent, and mixing process are the same or essentially the same, the amount of phosphorus-based additives added will affect the color stability of the composite material in a high-temperature and oxygen-rich environment.

[0089] In Example 4, the amount of phosphorus-based additives was relatively small, and the powder B value increased significantly over time, indicating that its inhibitory effect on the thermo-oxidative yellowing of nylon powder was relatively limited. In Example 5, after increasing the amount of phosphorus-based additives, the trend of the powder B value increasing over time was somewhat mitigated, and the thermo-oxidative yellowing phenomenon was improved. In Example 6, after further increasing the amount of phosphorus-based additives, the powder B value remained at a low level throughout the test, indicating that it could more effectively delay the yellowing of nylon powder under thermo-oxidative conditions.

[0090] This application improves the thermo-oxidative stability of nylon powder composites in high-temperature and oxygen-rich environments by adding phosphorus-based additives, slows down the increase of powder B value over time, thereby inhibiting yellowing of the material during the printing process and subsequent heat treatment, improving the appearance consistency of printed parts, and enhancing the stability of powder materials for repeated use.

[0091] Examples 1, 7, and 8 of this application compared the effect of melt leveling agent dosage on composite materials. In Example 7, the melt leveling agent dosage was relatively low. Although the composite material could be printed, the temperature range between the sintering temperature and the initial non-warping temperature was relatively narrow, indicating that the leveling effect of the powder during the heating and melting process was relatively limited. In Example 1, after increasing the melt leveling agent dosage, the composite material still maintained good ink absorbency and printability, and the surface condition of the printed parts was better. In Example 8, after further increasing the melt leveling agent dosage, the printable temperature window of the composite material was further improved, indicating that the melt leveling agent can improve the melt leveling effect of nylon powder during the heating and sintering process, which is beneficial to improving the molding stability of the printing process.

[0092] This application improves the melting and spreading state of nylon powder during the printing heating process by adding a melt leveling agent, widens the printable temperature window of the composite material, and reduces the graininess of the printed parts, thereby improving the surface quality and printing stability of the printed parts.

[0093] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A composite material for 3D printing, characterized in that, The product includes nylon powder and additives, wherein the nylon powder has a porosity of 10%-50% as determined by mercury intrusion porosimetry according to ISO 15901-1, a particle size range of 0.7-1.2 as determined by laser diffraction according to ISO 13320, and a median particle size D50 of 10 μm-100 μm; The additives include one or more of the following: antioxidants, powder flow aids, melt leveling agents, phosphorus-based additives, and color powders.

2. The composite material for 3D printing according to claim 1, wherein, Based on 100 parts by weight of the nylon powder, the composite material comprises 100 parts of nylon powder, 0-2 parts of antioxidant, 0-1 parts of powder flow aid, 0.1-1 parts of melt leveling agent, 0.1-2 parts of phosphorus-based additives, and 0-2 parts of color powder.

3. A composite material for 3D printing according to claim 1 or 2, characterized in that, The nylon powder includes one or more of nylon 1010, nylon 1012, nylon 11, and nylon 12.

4. A composite material for 3D printing according to any one of claims 1-3, characterized in that, The phosphorus-based additives include one or more of phosphoric acid, phosphorous acid, and sodium hypophosphite.

5. A composite material for 3D printing according to any one of claims 1-4, characterized in that, The melt leveling agent includes modified siloxane compounds.

6. A composite material for 3D printing according to any one of claims 1-5, characterized in that, The powder flow aid includes one or more of fumed silica, saponified metal salts, and alumina.

7. A composite material for 3D printing according to any one of claims 1-6, characterized in that, The antioxidants include one or more of the following: hindered amine antioxidants, cuprous iodide antioxidants, potassium iodide antioxidants, hindered phenolic antioxidants, phosphite antioxidants, and inorganic phosphate antioxidants.

8. A composite material for 3D printing according to any one of claims 1-7, characterized in that, The pigment includes one or more of titanium dioxide, carbon black, antimony tin oxide, lanthanum hexafluoride, and basic copper sulfate.

9. A method of producing a composite material as claimed in any one of claims 1 to 8, characterised in that: The nylon powder and additives are prepared by mixing in a high-speed mixer.

10. The method of claim 9, wherein the composite material is prepared by a method comprising: The mixing speed of the high-speed mixer is controlled at 800 rpm-1200 rpm; And / or, control the mixing time to 3-6 minutes.

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