Shear hardening flexible 3D printing material as well as preparation method and printing method thereof

Abstract

The invention discloses a shear hardening flexible 3D printing material as well as a preparation method and a printing method thereof. The shear hardening flexible 3D printing material comprises a shear hardening rubber and a thermoplastic polyurethane elastomer, and the shear hardening rubber and the thermoplastic polyurethane elastomer in the shear hardening flexible 3D printing material are a physical blending system and do not generate a chemical cross-linking reaction. The shear hardening flexible 3D printing material integrates shear hardening intelligent response, excellent flexibility and 3D printing customized forming performance, and can be widely applied to the fields of intelligent wearable equipment, impact protection devices, flexible intelligent structures and the like.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology and flexible functional materials, specifically to a shear-hardening flexible 3D printing material and its preparation and printing methods. Background Technology

[0002] Shear-hardening adhesives, as a class of smart functional materials based on polyborosiloxanes, have broad application prospects in the field of impact protection due to their unique strain rate enhancement effect. However, in existing technologies, shear-hardening adhesives are mostly dispersed in composite material systems as reinforcing phases, lacking fixed morphology and structural design capabilities, resulting in a prominent problem of structural uniformity. Patent CN113025050A discloses a composite material with shear-hardening and flame-retardant properties, comprising shear-hardening adhesive and flame-retardant particles. Patent CN117363025A discloses a freeze-resistant shear-hardening composite material composed of shear-hardening adhesive and low-temperature resistant silicone rubber.

[0003] Furthermore, with the deep integration of 3D printing technology and flexible functional materials, 3D printing has become a core technology for realizing the structural and customized development of flexible materials. Patent CN118975659B discloses a color-changing 3D printing material that significantly improves the gelation properties and 3D printing formability of pure inulin by combining inulin with metal salts. Patent CN120944280A discloses an engineering plastic 3D printing consumable that develops novel printing consumables through functional modification of plastics.

[0004] Based on currently available patents, research on flexible composite materials that simultaneously satisfy flexibility and 3D printing performance remains limited. In particular, research on complex structural designs using shear-stiffening adhesives based on additive manufacturing technology is extremely scarce. Therefore, developing a shear-stiffening flexible 3D printing material and its printing method that can retain the core functions of shear-stiffening adhesives, adapt to 3D printing processes, and exhibit stable molding performance is crucial to overcoming existing technological limitations and expanding application scenarios. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a shear-hardening flexible 3D printing material and its preparation method. While retaining the core functions and excellent flexibility of shear-hardening adhesives, the shear-hardening flexible 3D printing material effectively solves the technical bottleneck of being unable to independently design complex structures.

[0006] A further technical problem to be solved by the present invention is to provide a printing method for the above-mentioned shear-hardening flexible 3D printing material.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A shear-hardening flexible 3D printing material includes a shear-hardening adhesive and a thermoplastic polyurethane elastomer, wherein the shear-hardening adhesive and the thermoplastic polyurethane elastomer in the shear-hardening flexible 3D printing material are a physical blend system and no chemical cross-linking reaction occurs.

[0009] The shear-hardening adhesive in the shear-hardening flexible 3D printing material has a mass percentage content of no more than 25%.

[0010] The mass fraction of the shear-hardening adhesive in the shear-hardening flexible 3D printing material is preferably 10%-25%.

[0011] The shear-hardening adhesive is prepared by polymerization of hydroxyl silicone oil and boride; the boride is selected from one or more of boric acid, borate, and boron oxide; the mass ratio of hydroxyl silicone oil to boride is 10:1-30:1.

[0012] The thermoplastic polyurethane elastomer is in powder form.

[0013] The above-mentioned method for preparing shear-hardening flexible 3D printing material involves mixing shear-hardening adhesive and thermoplastic polyurethane elastomer. Specifically, shear-hardening adhesive and thermoplastic polyurethane elastomer are added to an open mill at a certain mass ratio and mixed at room temperature for 20-60 minutes to obtain the shear-hardening flexible 3D printing material.

[0014] The method for preparing the shear-hardening flexible 3D printing material further includes the following steps:

[0015] The shear-hardened flexible 3D printing material obtained by mixing is crushed into fragments;

[0016] The fragments are melted and extruded to obtain flexible 3D printing filaments.

[0017] The diameter of the flexible 3D printing filament is 1.75 mm ± 0.05 mm.

[0018] The above-mentioned printing method for shear-hardening flexible 3D printing materials, wherein the printing method employs fused deposition modeling (FDM) 3D printing, specifically includes the following steps:

[0019] (1) Model slicing: Import the preset 3D model into the slicing software and set the slicing parameters according to the characteristics of the wire and the printing requirements;

[0020] (2) Loading and printing: Load the shear-hardening flexible 3D printing material into the fused deposition modeling 3D printer and start printing according to the slicing parameters.

[0021] The nozzle diameter of the fused deposition modeling 3D printer is 0.4 mm or 0.8 mm, the nozzle temperature is 230-250 degrees Celsius, and the printing speed is 20-40 mm / s.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) The shear-hardening flexible 3D printing material of the present invention integrates shear-hardening intelligent response, excellent flexibility and 3D printing customized molding performance, and can be widely used in smart wearable devices, impact protection devices and flexible smart structures.

[0024] (2) The shear hardening flexible 3D printing material of the present invention, through the synergistic composite design of shear hardening adhesive and thermoplastic polyurethane elastomer, not only fully retains the rapid hardening buffer function of shear hardening adhesive under impact load, but also solves the technical pain point of traditional shear hardening materials being difficult to process and mold independently by taking advantage of the molding modification effect of thermoplastic polyurethane elastomer.

[0025] (3) The shear-hardening flexible 3D printing material of the present invention, combined with the fused deposition modeling 3D printing process, can directly adapt the standard filament made from the material to commercial printers. It can achieve precise molding of complex customized structures without equipment modification. While ensuring the flexibility and functional stability of the finished product, it greatly improves the structural design freedom and scene adaptability of the shear-hardening material. Attached Figure Description

[0026] Figure 1 Images of shear-hardening adhesive and thermoplastic polyurethane elastomer, the raw materials for preparing shear-hardening flexible 3D printing materials.

[0027] Figure 2 A physical image of the prepared shear-hardened flexible 3D printing material;

[0028] Figure 3 A photograph of the prepared flexible 3D printed filament;

[0029] Figure 4 The figures show the printability test results of the shear-hardening flexible 3D printing materials obtained in Examples 2 to 4 of the present invention.

[0030] Figure 5 The printing stability of the shear-hardening flexible 3D printing materials obtained in Examples 2 to 4 of the present invention;

[0031] Figure 6 The tensile properties of the shear-hardening flexible 3D printing materials obtained in Examples 2 to 4 of the present invention;

[0032] Figure 7The protective performance of the shear-hardening flexible 3D printing materials obtained in Examples 2 to 4 of the present invention under drop hammer impact;

[0033] Figure 8 This is a schematic diagram of the fabrication process of the flexible 3D printing filament of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The core of the shear-hardening flexible 3D printing material, its preparation method, and printing method of this invention lies in the synergistic system of "functional component-forming component-3D printing process." The shear-hardening flexible 3D printing material uses shear-hardening adhesive as the core functional component and thermoplastic polyurethane elastomer as the forming modification component, such as... Figure 8 As shown, the two are mechanically mixed and processed to form a flexible 3D printing filament adapted for fused deposition modeling (FDM) 3D printing. The printing method achieves customized structural forming of shear-hardened materials through standardized filament preparation and process parameter optimization, and has both intelligent response function and stable forming performance.

[0036] Furthermore, the core functional component, shear-hardening adhesive, is prepared by polymerization of hydroxyl silicone oil and boride, wherein the boride is selected from one or more of boric acid, borate, and boron oxide, preferably boric acid. The mass ratio of hydroxyl silicone oil to boride is 10:1-30:1, preferably 20:1; the polymerization reaction is carried out at 150-200 degrees Celsius for 1-4 hours to ensure full cross-linking of dynamic boron-oxygen bonds; after cooling to room temperature, a gel-like product with stable shear-hardening properties is obtained. This product maintains flexibility at low strain rates and can rapidly harden under impact loads to dissipate energy.

[0037] Furthermore, the molding modified component thermoplastic polyurethane elastomer is as follows: Figure 1 The powder form shown is used to increase the contact area with the shear-hardening adhesive, ensuring uniform mixing. The selected thermoplastic polyurethane elastomer must possess good thermoplasticity and flexibility, with a melting temperature suitable for the printing temperature range of 230-250 degrees Celsius. It should not undergo significant degradation at high temperatures and should be able to synergistically interact with the shear-hardening adhesive, ensuring the stability of the filament extrusion molding without compromising the core function of the shear-hardening adhesive.

[0038] Further, see Figure 8The shear-hardening flexible 3D printing material is prepared by mixing shear-hardening adhesive and thermoplastic polyurethane elastomer in a specific mass ratio. This mass ratio includes, but is not limited to, 0:100 (pure thermoplastic polyurethane elastomer control group), 10:90, and 20:80, preferably 20:80. During preparation, both materials are added to a two-roll mill and mixed at room temperature for 30 minutes to obtain the desired result. Figure 2 The image shows a uniformly dispersed block without agglomeration or stratification.

[0039] Furthermore, the blocky precursor needs to be cut into small fragments with a particle size of approximately 5 mm. These fragments are then fed into a single-screw extruder and melt-extruded to obtain a product with a uniform wire diameter. Figure 3 The flexible 3D printing filament shown is 1.75 mm ± 0.05 mm in diameter. This specification is the standard size for commercial fused deposition modeling (FDM) 3D printers and can be used directly without structural or parameter modifications to the equipment.

[0040] Furthermore, the 3D printing method is a fused deposition modeling (FDM) 3D printing process, and the printable structures include, but are not limited to, standard elongated tensile parts and standard square drop-weight specimens. The standard elongated tensile part is a cuboid with dimensions of 80 mm × 20 mm × 2 mm, and the standard square drop-weight specimen is a cuboid with dimensions of 30 mm × 30 mm × 3 mm.

[0041] Furthermore, the recommended key parameters for the fused deposition modeling 3D printing are as follows: nozzle diameter can be selected as 0.4 mm or 0.8 mm, nozzle temperature is 230-250 degrees Celsius, and printing speed is 20-40 mm / s; the combination of nozzle temperature and printing speed needs to be adjusted according to the nozzle diameter to ensure that the filament is fully melted and smoothly extruded.

[0042] The method for preparing shear-hardening flexible 3D printing material and printing finished products according to the present invention includes the following steps:

[0043] a. Preparation of shear-hardening adhesive: Hydroxy silicone oil and boride are mixed evenly at a mass ratio of 10:1-30:1, reacted at 180 degrees Celsius for 2 hours, and then cooled to room temperature to obtain shear-hardening adhesive.

[0044] b. Preparation of precursor: The shear-hardening rubber obtained in step a is mixed with powdered thermoplastic polyurethane elastomer at a mass ratio of 0:100, 10:90 or 20:80, and then mixed in a two-roll mill at room temperature for 30 minutes to obtain a uniformly dispersed block.

[0045] c. Pre-treatment of precursors: The blocky precursors are cut into small pieces with a particle size of about 5 mm to ensure smooth feeding.

[0046] d. Preparation of printing filament: The precursor fragments obtained in step c are added to a single screw extruder and melt-extruded to obtain a flexible 3D printing filament with a diameter of 1.75 mm ± 0.05 mm.

[0047] e. Model slicing: Import a preset 3D model into the slicing software and set slicing parameters such as layer thickness, infill density, and support type according to printing requirements.

[0048] f. Loading and printing: Load the flexible 3D printing filament obtained in step d into a commercial fused deposition modeling (FDM) 3D printer, set the parameters to a nozzle diameter of 0.4 mm or 0.8 mm, a nozzle temperature of 230-250 degrees Celsius, and a printing speed of 20-40 mm / s, and start the printer to build up the filament layer by layer to obtain the target structure.

[0049] Example 1:

[0050] This embodiment prepares a shear-hardening flexible 3D printing material, including the following steps:

[0051] S0: Preparation of shear-hardening adhesive. Specifically, 100g of hydroxyl silicone oil and 10g of boric acid are placed in an oven and reacted at 180 degrees Celsius for 2 hours to obtain shear-hardening adhesive;

[0052] S1: Mix 10g of shear-hardening adhesive and 90g of thermoplastic polyurethane elastomer powder in a two-roll mill for 30 minutes to obtain a shear-hardening flexible 3D printing material block.

[0053] S2: Cut the shear-hardened flexible 3D printing material precursor into small fragments with a particle size of about 5 mm;

[0054] S3 adds small fragments to a single-screw extruder and melts them to produce flexible 3D printing filaments with uniform diameter.

[0055] Example 2:

[0056] This embodiment prepares a shear-hardening flexible 3D printing material, including the following steps:

[0057] S0: Preparation of shear-hardening adhesive. Specifically, 200g of hydroxyl silicone oil and 10g of boric acid are placed in an oven and reacted at 180 degrees Celsius for 2 hours to obtain shear-hardening adhesive;

[0058] S1: Mix 10g of shear-hardening adhesive and 90g of thermoplastic polyurethane elastomer powder in a two-roll mill for 30 minutes to obtain a shear-hardening flexible 3D printing material block.

[0059] S2: Cut the shear-hardened flexible 3D printing material precursor into small fragments with a particle size of about 5 mm;

[0060] S3 adds small fragments to a single-screw extruder and melts them to produce flexible 3D printing filaments with uniform diameter.

[0061] Example 3:

[0062] This embodiment prepares a shear-hardening flexible 3D printing material, including the following steps:

[0063] S0: Preparation of shear-hardening adhesive. Specifically, 200g of hydroxyl silicone oil and 10g of boric acid are placed in an oven and reacted at 180 degrees Celsius for 2 hours to obtain shear-hardening adhesive;

[0064] S1: Mix 20g of shear-hardening adhesive and 80g of thermoplastic polyurethane elastomer powder in a two-roll mill for 30 minutes to obtain a shear-hardening flexible 3D printing material block.

[0065] S2: Cut the shear-hardened flexible 3D printing material precursor into small fragments with a particle size of about 5 mm;

[0066] S3 adds small fragments to a single-screw extruder and melts them to produce flexible 3D printing filaments with uniform diameter.

[0067] Example 4:

[0068] The 3D printing material in this embodiment contains only thermoplastic polyurethane elastomer, and includes the following steps:

[0069] S1: Place 100 grams of thermoplastic polyurethane elastomer powder into a two-roll mill and mix for 30 minutes to obtain a shear-hardened flexible 3D printing material block;

[0070] S2: Cut the shear-hardened flexible 3D printing material precursor into small fragments with a particle size of about 5 mm;

[0071] S3 adds small fragments to a single-screw extruder and melts them to produce flexible 3D printing filaments with uniform diameter.

[0072] Example 5:

[0073] This embodiment prepares a shear-hardening flexible 3D printing material, including the following steps:

[0074] S0: Preparation of shear-hardening adhesive. Specifically, 300g of hydroxyl silicone oil and 10g of boric acid are placed in an oven and reacted at 180 degrees Celsius for 2 hours to obtain shear-hardening adhesive;

[0075] S1: Mix 20g of shear-hardening adhesive and 80g of thermoplastic polyurethane elastomer powder in a two-roll mill for 30 minutes to obtain a shear-hardening flexible 3D printing material block.

[0076] S2: Cut the shear-hardened flexible 3D printing material precursor into small fragments with a particle size of about 5 mm;

[0077] S3 adds small fragments to a single-screw extruder and melts them to produce flexible 3D printing filaments with uniform diameter.

[0078] Example 6:

[0079] The printing method of the shear-hardening flexible 3D printing material of the present invention is as follows:

[0080] The flexible 3D printing filament obtained in the above embodiments is loaded into a commercial fused deposition modeling 3D printer. The parameters are set as follows: nozzle diameter 0.4 mm, nozzle temperature 250 degrees Celsius, and printing speed 30 mm / s. The printer is started to deposit the filament layer by layer to obtain the target structure.

[0081] The performance parameters of the samples obtained in the above embodiments were tested according to the following test methods:

[0082] A. The specific method for measuring the 3D printability of this invention is as follows:

[0083] A cylindrical structure was selected as the printing model, with dimensions of 15 mm in diameter and 12 mm in height. A fused deposition modeling (FDM) 3D printer was used for printing, with the following parameters set: nozzle diameter 0.4 mm, nozzle temperature 250 degrees Celsius, and printing speed 30 mm / s. After printing, the formed product was observed to evaluate its printability. Figure 4 As shown, the printed products obtained by using different proportions of filament in Examples 2 to 4 exhibited high stability during the molding process. They all printed complete cylindrical structures with smooth surfaces and clear edges, and no extrusion instability or molding defects caused by shear hardening and increased glue content occurred.

[0084] B. The specific method for measuring the molding stability of shear-stiffened flexible 3D printing materials is as follows:

[0085] Printed products with a "shear-hardening adhesive content of 20%" from Test Method A were selected as test samples. The samples were placed in a standard environment at room temperature and allowed to stand for 1 hour, 1 day, and 7 days. After each time point, the samples were observed for signs of creep leading to structural loosening, thus evaluating the molding stability of the printed products. Figure 5 As shown, the shear-hardening flexible 3D printing material of the present invention has excellent molding stability. Under observation at various time points, the printed product did not show defects such as deformation, cracking, warping or loose structure. It can stably maintain the preset 3D printing structure shape and can meet the stability requirements of material storage and long-term use in actual application scenarios.

[0086] C. The specific method for measuring the tensile properties of finished products printed from shear-stiffened flexible 3D printing materials is as follows:

[0087] Shear-stiffening flexible 3D printing materials with different compositions were used to fabricate elongated samples via fused deposition modeling (FDM). The samples had a thickness of 2 mm, a length of 80 mm, and a width of 20 mm. Their uniaxial tensile properties were then characterized using a commercial electronic universal testing machine (Criterion™ Model 43, Mester Industrial). Figure 6 As shown, compared with the printing material without shear-hardening binder (ratio 0:100), the tensile strain capacity and flexibility of the 3D printing material with shear-hardening binder are enhanced, and the enhancement of tensile strain capacity and flexibility is further expanded with the increase of shear-hardening binder content (from 10% to 20%).

[0088] D. The specific methods for measuring the protective performance of shear-stiffened flexible 3D printing materials under low-speed impact are as follows:

[0089] Cubic samples were fabricated using fused deposition modeling (FDM) 3D printing with different compositions of shear-stiffened flexible 3D printing materials. The samples were 3 mm thick, 30 mm long, and 30 mm wide. A drop hammer impact testing system was used, including an electromagnetically driven drop hammer release platform (ZCJ1302-A, MTS), a dynamic load sensor (KD3005C, Yangzhou Kedong), a digital oscilloscope (Tektronix DPO2014B), and a charge amplifier (YE5853, Donghua Testing). A 500-gram blunt-tipped drop hammer was released from different initial heights. The dynamic load sensor was placed under the cubic samples. The force signal evolution during the impact process was acquired using the charge amplifier and digital oscilloscope. Figure 7 As shown, the peak force of the 3D printing material with added shear-hardening binder showed a significant decreasing trend with the increase of shear-hardening binder content at all impact energies. This result directly verifies that the higher the shear-hardening binder content, the more significant the enhancement effect on impact resistance.

[0090] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0091] The parts of this invention not described in detail are well-known in the art. The above embodiments are provided merely for the purpose of describing the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A shear-hardening flexible 3D printing material, characterized in that, The shear-hardening flexible 3D printing material includes shear-hardening adhesive and thermoplastic polyurethane elastomer. The shear-hardening adhesive and the thermoplastic polyurethane elastomer in the shear-hardening flexible 3D printing material are a physical blend system and no chemical cross-linking reaction has occurred.

2. The shear-hardening flexible 3D printing material according to claim 1, characterized in that, The shear-hardening adhesive in the shear-hardening flexible 3D printing material has a mass percentage content of no more than 25%.

3. The shear-stiffening flexible 3D printing material according to claim 2, characterized in that, The mass fraction of the shear-hardening adhesive in the shear-hardening flexible 3D printing material is preferably 10%-25%.

4. The shear-hardening flexible 3D printing material according to claim 1, characterized in that, The shear-hardening adhesive is prepared by polymerization of hydroxyl silicone oil and boride; the boride is selected from one or more of boric acid, borate, and boron oxide; the mass ratio of hydroxyl silicone oil to boride is 10:1-30:

1.

5. The shear-hardening flexible 3D printing material according to claim 1, characterized in that, The thermoplastic polyurethane elastomer is in powder form.

6. The method for preparing the shear-hardening flexible 3D printing material according to any one of claims 1 to 5, characterized in that, The shear-hardening flexible 3D printing material is formed by mixing shear-hardening adhesive and thermoplastic polyurethane elastomer. Specifically, the shear-hardening adhesive and thermoplastic polyurethane elastomer are added to a two-roll mill at a certain mass ratio and mixed at room temperature for 20 to 60 minutes to obtain the shear-hardening flexible 3D printing material.

7. The method for preparing the shear-hardening flexible 3D printing material according to claim 6, characterized in that, The method for preparing the shear-hardening flexible 3D printing material further includes the following steps: The shear-hardened flexible 3D printing material obtained by mixing is crushed into fragments; The fragments are melted and extruded to obtain flexible 3D printed filaments.

8. The method for preparing the shear-hardening flexible 3D printing material according to claim 7, characterized in that, The diameter of the flexible 3D printing filament is 1.75 mm ± 0.05 mm.

9. The printing method of the shear-hardening flexible 3D printing material according to any one of claims 1 to 5, characterized in that, The printing method employs fused deposition modeling (FDM) 3D printing and specifically includes the following steps: (1) Model slicing: Import the preset 3D model into the slicing software and set the slicing parameters according to the characteristics of the wire and the printing requirements; (2) Loading and printing: Load the shear-hardening flexible 3D printing material according to any one of claims 1 to 5 into the fused deposition modeling 3D printer and start printing according to the slicing parameters.

10. The printing method of the shear-hardening flexible 3D printing material according to claim 9, characterized in that, The nozzle diameter of the fused deposition modeling 3D printer is 0.4 mm or 0.8 mm, the nozzle temperature is 230-250 degrees Celsius, and the printing speed is 20-40 mm / s.

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