Preparation method and application of high-elongation-at-break flexible self-healing heat-conducting composite material for robot

Abstract

The invention discloses a preparation method and application of a high-elongation-at-break flexible self-healing heat-conducting composite material for a robot. The composite material is prepared by taking polycaprolactone diol, isocyanate, dimethylglyoxime and spherical aluminum oxide as raw materials, constructing a polyurethane matrix with a'dynamic-permanent 'double-crosslinking network structure and regulating and controlling the content of the spherical aluminum oxide. Wherein the permanent cross-linked network provides a rigid framework and high-strength support; a dynamic cross-linked network (composed of hydrogen bonds and dynamic oxime-urethane bonds) endows the material with energy dissipation capability and self-repairing characteristics. The spherical aluminum oxide filler has double functions in the system: the spherical aluminum oxide filler is used as a rigid reinforcing phase to improve the mechanical property; the heat conductivity coefficient is obviously improved as a high-efficiency heat-conducting channel. The composite material has high tensile strength, ultrahigh elongation at break and excellent bendability, and can self-repair damage for multiple times. The method is simple in preparation process and low in cost, and has wide application prospects in the fields of heat dissipation of flexible wearable electronic equipment and the like.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive composite materials technology, and specifically relates to a method for preparing and applying a flexible self-healing thermally conductive composite material with high elongation at break for robots. Background Technology

[0002] As semiconductor devices evolve towards miniaturization, high integration, and high power density, their heat generation increases dramatically. Thermal failure has become the primary problem hindering the performance and lifespan of microelectronic packaged devices. The development of thermal interface materials has become a technological bottleneck restricting the improvement of computing speed, functionality, and reliability of electronic chips, as well as the extension of their service life.

[0003] Polyurethane is considered a promising matrix material due to its highly designable molecular structure, ease of processing and molding, excellent flexibility, and superior damping properties. However, its inherently low thermal conductivity (typically 0.1-0.3 W / (m·K)) severely limits its application performance in high heat flux density scenarios. Current mainstream solutions involve composites of polymer matrices (such as silicone rubber, epoxy resin, and polyolefins) with high thermal conductivity fillers (such as metal powders, ceramic particles, and carbon materials). While filling the polymer matrix with a large amount of thermally conductive filler can effectively improve the thermal conductivity of the composite material, this often comes with negative effects such as a significant increase in the material's elastic modulus, decreased flexibility, increased internal stress, and increased interfacial contact thermal resistance.

[0004] More importantly, traditional composite materials generally rely on irreversible chemical cross-linking reactions (such as peroxide vulcanization of silicone rubber and amine curing of epoxy resin) to form a three-dimensional network structure, endowing the material with the necessary mechanical strength and thermal stability. This chemical cross-linking structure results in the material exhibiting "infusible and insoluble" properties. This irreversibility brings significant limitations: on the one hand, once the material has been cured or used, it is difficult to reprocess, repair, or recycle it through melting or dissolving; on the other hand, waste materials, scraps, and thermal interface material layers generated during manufacturing, as well as those from discarded devices, cannot be effectively recycled. This not only wastes resources but also brings increasingly serious challenges to electronic waste (E-waste) disposal and environmental pollution. Therefore, in practical applications, how to endow composite materials with high thermal conductivity, low modulus, high toughness, and reprocessable properties is a crucial problem that urgently needs to be solved. Summary of the Invention

[0005] To address the aforementioned issues, the present invention aims to provide a method for preparing and applying a flexible, self-healing, thermally conductive composite material with high elongation at break for robotic applications. This preparation process is simple and efficient, and precisely controls the mass ratio of soft to hard segments, the content of polymethylene polyphenyl isocyanate, and the content of spherical alumina, resulting in a material with excellent flexibility, self-healing properties, and thermal conductivity. The elongation at break is ≥1000%, enabling it to withstand repeated bending and thermal stress deformation while avoiding interfacial delamination failure.

[0006] To address the problems in the existing technology, the technical solution adopted by this invention is as follows:

[0007] A method for preparing a flexible, self-healing, thermally conductive composite material with high elongation at break for robots includes the following steps:

[0008] Step 1, Synthesize the prepolymer:

[0009] Polycaprolactone diol at 100-120 o Water removal treatment at temperature C, cooling down by 40-80°C o At temperature C, add the isocyanate blend and heat at 60-90°C. o The reaction is carried out at C for 60-300 min to obtain polyurethane prepolymer;

[0010] Step 2, Composite Dispersion:

[0011] Weigh alumina and disperse it evenly in a vacuum planetary system with the polyurethane prepolymer; dissolve dimethylglyoxime in tetrahydrofuran and stir magnetically at room temperature for 30-60 min to obtain a clear dimethylglyoxime solution with a concentration of 0.04-0.2 g / mL; weigh the dimethylglyoxime solution and add it to the mixture, then disperse it evenly in a vacuum planetary system.

[0012] Step 3, Curing and Shaping:

[0013] Pour the mixture into a PTFE mold and degas at room temperature (60-100°C). o Curing at C for 48-72 hours yields the composite material.

[0014] As an improvement, the alumina is spherical alumina with a particle size ranging from 1 to 100 μm.

[0015] As an improvement, the molecular weight of polycaprolactone diol is 500-1500, and the NCO group content of the polyurethane prepolymer is 5-10%.

[0016] As an improvement, the mass ratio of soft segments to hard segments in polyurethane is (50-80):(20-50).

[0017] As an improvement, the mass ratio of alumina to polyurethane matrix is ​​(30-70):100.

[0018] As an improvement, the functionality of the isocyanate blend is 2-3.

[0019] As an improvement, the isocyanate blend includes one or two of isophorone diisocyanate and dicyclohexylmethane diisocyanate, and then with polymethylene polyphenyl polyisocyanate, wherein the polymethylene polyphenyl polyisocyanate accounts for 2-10% of the total mass of the isocyanate.

[0020] As an improvement, the cured material in step 3 has self-healing properties, and the repair conditions are heat treatment at 60-120℃ for 10-180 min.

[0021] As an improvement, the NCO index of the high elongation at break flexible self-healing thermally conductive composite material is 1-1.05.

[0022] Applications of high elongation at break flexible self-healing thermally conductive composite materials prepared by any of the above methods in the preparation of flexible wearable electronic devices or robot heat dissipation.

[0023] Beneficial effects:

[0024] This invention precisely controls the mass ratio of soft to hard segments, the content of polymethylene polyphenyl polyisocyanate, and the content of spherical alumina, giving the material excellent flexibility, self-healing properties, and thermal conductivity. The elongation at break is ≥1000%, allowing it to withstand repeated bending and thermal stress deformation, avoiding interfacial delamination failure. The dimethylglyoxime forms dynamic oxime-carbamate bonds with the polyurethane hard segments, enabling it to autonomously repair processing damage or microcracks, extending the thermal management life of the device. The preparation process of this invention is simple and efficient, and it has broad application prospects. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the microstructure of the composite material prepared in Example 1 of the present invention.

[0026] Figure 2 This is a SEM microstructure image of the composite material prepared in Example 1 of this invention.

[0027] Figure 3 This is a graph showing the mechanical properties of the composite material prepared in Example 1 of this invention.

[0028] Figure 4 These are the mechanical property curves of Example 2 and Comparative Example 2.

[0029] Figure 5 These are the self-healing mechanical properties and tensile photographs of the composite material prepared in Example 1 of this invention. Detailed Implementation

[0030] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough understanding of the disclosure of the present invention.

[0031] Example 1:

[0032] Add 5 g of polycaprolactone diol to a three-necked flask, and heat at 120°C. o Vacuum stirring at C for 2 hours to remove water; then reduce to 50°C. o After temperature C, add 2.7 g IPDI and 0.13 g pm200, then heat to 80°C. o React at C for 4 h to synthesize isocyanate-terminated polyurethane prepolymers. Weigh 5.1 g of spherical alumina and 4.6 g of polyurethane prepolymer into a mixing flask and disperse evenly under vacuum. Then add anhydrous tetrahydrofuran solution (0.5 g of dimethylglyoxime) dissolved in 10 ml of dimethylglyoxime, mix and disperse under vacuum, pour the mixture into a polytetrafluoroethylene mold, and incubate at 80°C. o After curing at C for 48 h, a thermally conductive composite material was obtained with an NCO index of 1.05.

[0033] Example 2:

[0034] Add 5 g of polycaprolactone diol to a three-necked flask, and heat at 120°C. o Vacuum stirring at C for 2 hours to remove water; then reduce to 50°C. o After temperature C, add 2.7 g IPDI and 0.13 g pm200, then heat to 80°C. o React at C for 4 h to synthesize isocyanate-terminated polyurethane prepolymer. Weigh 25.5 g of spherical alumina and 4.6 g of polyurethane prepolymer into a mixing flask and disperse evenly. Then add anhydrous tetrahydrofuran solution (0.5 g of dimethylglyoxime) dissolved in 10 ml of dimethylglyoxime, mix and disperse under vacuum, pour the mixture into a polytetrafluoroethylene mold, and incubate at 80°C. o After curing at C for 48 h, a thermally conductive composite material was obtained with an NCO index of 1.05.

[0035] Example 3:

[0036] Add 5 g of polycaprolactone diol to a three-necked flask, and heat at 120°C. o Vacuum stirring at C for 2 hours to remove water; then reduce to 50°C. o After temperature C, add 2.7 g HMDI and 0.13 g pm200, then heat to 80°C. oReact at C for 4 h to synthesize isocyanate-terminated polyurethane prepolymer. Weigh 31.5 g of spherical alumina and 5.8 g of polyurethane prepolymer into a mixing flask and disperse evenly. Then add anhydrous tetrahydrofuran solution (0.5 g of dimethylglyoxime) dissolved in 10 ml of dimethylglyoxime, mix and disperse under vacuum, pour the mixture into a polytetrafluoroethylene mold, and incubate at 80°C. o After curing at C for 48 h, a thermally conductive composite material was obtained with an NCO index of 1.03.

[0037] Comparative Example 1:

[0038] Unlike Example 1, no alumina filler was added.

[0039] Comparative Example 2:

[0040] Unlike Example 1, 80% spherical alumina was added.

[0041] Comparative Example 3:

[0042] Add 5 g of polycaprolactone diol to a three-necked flask, and heat at 120°C. o Vacuum stirring at C for 2 hours to remove water; then reduce to 50°C. o After temperature C, add 2.7 g IPDI and 0.54 g pm200, then heat to 80°C. o React at C for 4 h to synthesize isocyanate-terminated polyurethane prepolymers. Add 0.5 g of dimethylglyoxime dissolved in 10 ml of anhydrous tetrahydrofuran, mix and disperse under vacuum, pour the mixture into a polytetrafluoroethylene mold, and heat at 80°C. o C was cured for 48 h to obtain Comparative Example 3.

[0043] The difference from Example 1 is that the PM200 content is increased.

[0044] Performance testing:

[0045] Thermal conductivity test: The thermal conductivity of the material is tested using a steady-state thermal conductivity meter. The test is performed three times and the average value is taken.

[0046] Mechanical property testing: The tensile strength and elongation at break of the material were tested using a universal testing machine. The test was performed three times, and the average value was taken.

[0047] Self-healing test: The material was cut in half and placed at 80°C. o The samples were subjected to self-healing in a C-type oven for 3 hours without any additional pressure or external stimulation during the healing process. The mechanical properties of the samples were then tested using a universal testing machine. The self-healing efficiency was calculated using a formula:

[0048]

[0049] Where η is the self-repair efficiency. The tensile strength of the material after repair. This represents the original strength of the material.

[0050] The embodiments and comparative examples underwent various performance tests, and the test results are shown in Table 1.

[0051] Table 1. Statistical table of performance test results for Examples 1-3 and Comparative Examples 1-3

[0052]

[0053] Comparing Example 1 and Comparative Example 1, Comparative Example 1, without the addition of spherical alumina, exhibited very low thermal conductivity and tensile strength in its pure polyurethane, indicating that spherical alumina enhances both thermal conductivity and mechanical properties. Comparing Example 1 and Comparative Example 2, Comparative Example 2, with the addition of 80% alumina, showed a significant decrease in mechanical properties, demonstrating that excessive alumina filler reduces the material's mechanical strength. Comparing Example 1 and Comparative Example 3, the addition of a higher amount of polymethylene polyphenyl polyisocyanate resulted in an excessive number of permanent cross-linked networks within the material, leading to a decrease in self-healing properties.

[0054] The above description is merely a preferred embodiment of the present invention. It should be noted that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Moreover, after reading the contents of the present invention, those skilled in the art can make various modifications or alterations to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing a high-elongation-at-break flexible self-healing thermally conductive composite material for robots, characterized in that, The method comprises the following steps: Step 1, synthesis of prepolymer: The polycaprolactone diol is treated under water removal at 100-120 o C for 60-300 min to obtain a polyurethane prepolymer. o C, and the isocyanate blend is added at 60-90 o C for 60-300 min to obtain a polyurethane prepolymer. Step 2, composite dispersion: Alumina is weighed and uniformly dispersed with polyurethane prepolymer in a vacuum planetary mixer; dimethylglyoxime is dissolved in tetrahydrofuran, and the solution is magnetically stirred at room temperature for 30-60 min to obtain a clear dimethylglyoxime solution with a concentration of 0.04-0.2 g / mL; the dimethylglyoxime solution is weighed and added to the mixture, and uniformly dispersed in a vacuum planetary mixer; Step 3, curing and forming: The mixture was poured into a polytetrafluoroethylene mold, degassed at room temperature, and cured at 60-100 o C for 48-72 h to obtain a composite material.

2. The method for preparing a high elongation at break flexible self-healing thermally conductive composite material for robots according to claim 1, characterized in that: The alumina is spherical alumina with a particle size range of 1-100 mm.

3. The method for preparing a high elongation at break flexible self-healing thermally conductive composite material for robots according to claim 1, characterized in that: The molecular weight of the polycaprolactone diol is 500-1500, and the NCO group content of the polyurethane prepolymer is 5-10%.

4. The method for preparing a high elongation at break flexible self-healing thermally conductive composite material for robots according to claim 1, characterized in that: The mass ratio of the soft segment and the hard segment of the polyurethane is (50-80):(20-50).

5. The method for preparing a high elongation at break flexible self-healing thermally conductive composite material for robots according to claim 1, characterized in that: The mass ratio of alumina to polyurethane matrix is (30-70):

100.

6. The method for preparing a high elongation at break flexible self-healing thermally conductive composite material for robots according to claim 1, characterized in that: The functionality of the isocyanate blend is 2-3.

7. The method for preparing a high elongation at break flexible self-healing thermally conductive composite material for robots according to claim 1, characterized in that: The isocyanate blend contains one or both of isophorone diisocyanate and dicyclohexylmethane diisocyanate, and is mixed with polymethylene polyphenyl polyisocyanate, and the polymethylene polyphenyl polyisocyanate accounts for 2-10% of the total mass of the isocyanate.

8. A method for preparing a high elongation at break flexible self-healing thermally conductive composite material for robots according to claim 1, characterized in that: The material after curing in step 3 has self-repairing properties, and the repair conditions are heat treatment at 60-120℃ for 10-180 min.

9. The method of claim 1, wherein the method further comprises: providing a mixture of a thermally conductive material, a polymer, and a curing agent; and mixing the mixture to form a thermally conductive material-polymer-curing agent mixture. The NCO index of the high-elongation flexible self-healing thermal conductive composite material is 1-1.

05.

10. Application of the high-elongation flexible self-healing thermal conductive composite material prepared by the preparation method of any one of claims 1-9 in the preparation of flexible wearable electronic devices or robot heat dissipation.

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