Thermally conductive pp material and method for producing the same

Abstract

The application relates to the technical field of high polymer materials, and discloses a heat-conducting PP material and a preparation method thereof. The PP material prepared by the application is prepared by extruding and granulating after blending of polypropylene as a main base material, addition of a heat-conducting reinforcing agent, maleic anhydride grafted polyethylene, ethylene-octene copolymer, an antioxidant and lubricant and other auxiliaries; the heat-conducting reinforcing agent added in the PP material improves the heat-conducting performance and impact resistance of the material while maintaining the mechanical performance. Therefore, the comprehensive performance of the material is improved, so that the material can be widely applied in the fields of electronic device shells, LED lighting heat-dissipation shells, relay shells and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a thermally conductive PP material and its preparation method. Background Technology

[0002] Polypropylene (PP), as one of the five major general-purpose plastics, occupies a pivotal position in the automotive, home appliance, and electronics industries due to its advantages such as wide availability, low density, chemical resistance, ease of processing and molding, and low cost. However, pure PP resin has extremely poor thermal conductivity, with its intrinsic thermal conductivity typically ranging from 0.2 to 0.26 W / (m·K). This inherent thermal limitation severely restricts its development in applications requiring efficient heat dissipation or heat transfer, such as LED lighting heat sinks, thin-walled electronic device housings, and chemical heat exchangers.

[0003] To address the bottleneck of poor thermal conductivity in polymers, domestic and international research has mainly followed two technical routes: one is to synthesize intrinsically thermally conductive polymers with highly ordered molecular chain structures; the other is to fill polymer matrices with high thermal conductivity fillers through physical blending to prepare filled thermally conductive composite materials. Among these, filled thermally conductive composite materials have become the mainstream research and industrialization direction due to their simple preparation process, controllable cost, and significant improvement in thermal conductivity. In the research of filled thermally conductive PP materials, how to efficiently construct a "thermal conductive network" and reduce the "interfacial thermal resistance" between the filler and the matrix are two core technical challenges. Traditional single fillers such as alumina, graphite, or boron carbide, while possessing certain thermal conductivity, often face problems in practical applications, such as excessive addition leading to deterioration of the composite material's mechanical properties, or uneven dispersion of the filler in the matrix, making it difficult to form effective pathways. Therefore, to address the current problems with thermally conductive PP materials, it is necessary to develop a PP material that combines mechanical properties, impact resistance, and high thermal conductivity to meet practical application requirements. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a thermally conductive PP material and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: A thermally conductive PP material, comprising the following raw materials in parts by weight: 60-80 parts polypropylene, 15-25 parts thermal conductivity enhancer, 8-15 parts maleic anhydride grafted polyethylene, 5-10 parts ethylene-octene copolymer, 0.5-2 parts antioxidant, and 1-2 parts lubricant. Furthermore, the antioxidant includes a primary antioxidant and a secondary antioxidant, and the ratio of the two is 1:1-2; Furthermore, the primary antioxidant is antioxidant 1010 or antioxidant 1076, and the secondary antioxidant is antioxidant 168; Furthermore, the lubricant is either silicone powder or polyethylene wax; The thermal conductivity enhancer is prepared by the following steps: Step A1: Mix glucose and tannic acid in deionized water and stir until homogeneous. Then add K2FeO4 and (NH4)2C2O4 and continue stirring for 30-50 minutes. Then transfer to an oven at 110℃ for pre-foaming for 12 hours. Then place in a tube furnace and heat-treat at 750℃ under nitrogen for 2 hours. Cool to room temperature, wash three times with 0.1mol / L dilute hydrochloric acid, then wash with water until neutral, dry, and grind to obtain PGC (porous graphitized carbon). Furthermore, in step A1, the ratio of glucose, tannic acid, deionized water, K2FeO4 and (NH4)2C2O4 is 1-1.5g:0.3-0.5g:30mL:1.2-1.5g:2-2.5g.

[0006] Step A2: Disperse PGC in a mixture of ethanol and deionized water by sonication for 40-60 min, add dopamine hydrochloride and stir until homogeneous, adjust the pH to 8.5 with Tris-HCl buffer, stir at room temperature for 24 h, filter, wash and dry to obtain PDA@PGC (polydopamine-coated porous graphitized carbon). Furthermore, in step A2, the ratio of PGC, ethanol, deionized water, and dopamine hydrochloride is 0.5g:80mL:20mL:0.3-0.5g.

[0007] Step A3: Disperse PDA@PGC in deionized water using ultrasound for 20 min, add aluminum nitrate nonahydrate and stir for 40-60 min, then add 0.5 mol / L ammonia solution dropwise and continue stirring for 1 h. Filter and wash until the filtrate is free of Al. 3+ Vacuum dried, then placed in a tube furnace and calcined at 600°C for 2 hours under argon atmosphere to obtain Al2O3@PGC (alumina-supported porous graphitized carbon). Furthermore, in step A3, the ratio of PDA@PGC, deionized water, aluminum nitrate nonahydrate, and ammonia is 0.1g:100mL:0.3-0.5g:6-10mL; Furthermore, the polydopamine coating in the PDA@PGC is calcined at 600°C to form a nitrogen-doped carbon material, which can also improve the thermal conductivity of porous graphitized carbon.

[0008] Step A4: Stir the titanate coupling agent OL-T951 in toluene until homogeneous, add Al2O3@PGC and ultrasonically disperse for 0.5-1 h, then heat to 80-90℃ and stir for 30-50 min. Filter, wash and vacuum dry to obtain the thermal conductivity enhancer. Furthermore, in step A4, the ratio of titanate coupling agent OL-T951, toluene, and Al2O3@PGC is 0.005-0.02g:50mL:1g.

[0009] A method for preparing a thermally conductive PP material includes the following steps: Weigh the raw materials according to the weight parts, add polypropylene, thermal conductivity enhancer, maleic anhydride grafted polyethylene, ethylene-octene copolymer, antioxidant and lubricant into a mixer and mix evenly, then transfer to a twin-screw extruder and extrude and granulate to obtain thermally conductive PP material. Furthermore, the temperatures of each section of the twin-screw extruder are as follows: Zone 1 180-200℃, Zone 2 200-210℃, Zone 3 210-220℃, Zone 4 210-220℃, Zone 5 200-210℃, Zone 6 190-210℃, and the die head 200-220℃.

[0010] The beneficial effects of this invention are: The PP material prepared by this invention uses polypropylene as the main matrix material, and adds thermal conductivity enhancers, maleic anhydride-grafted polyethylene, ethylene-octene copolymer, antioxidants, lubricants, and other additives, followed by extrusion granulation. The added thermal conductivity enhancers in this PP material improve the thermal conductivity and impact resistance of the material while maintaining its mechanical properties. Therefore, the improved overall performance of this material enables its wide application in fields such as electronic device housings, LED lighting heat dissipation housings, and relay housings.

[0011] The thermal conductivity enhancer introduced in the PP material of this invention provides better thermal conductivity and heat dissipation performance compared to traditional thermally conductive fillers, while also exhibiting good interfacial and dispersion properties within the matrix material. This thermal conductivity enhancer is prepared by loading nano-alumina onto porous graphitized carbon and then treating it with a titanate coupling agent. Porous graphitized carbon, due to its extremely high intrinsic thermal conductivity, allows phonons to pass through its sp² hybridized carbon atom layers at high speeds, much like on a highway. Its porous structure not only increases the specific surface area but, more importantly, provides numerous sites for the loaded alumina, ensuring uniform distribution and interconnection of the alumina and preventing agglomeration. Furthermore, this structural design allows multiple composite particles to more easily overlap within the PP matrix, forming a three-dimensional thermally conductive network that permeates the entire material. The high thermal conductivity alumina loaded onto the graphitized carbon skeleton acts as "nodes," filling the voids between the carbon materials and bridging the thermal conductivity network. This allows heat to be rapidly transferred along the graphitized carbon while simultaneously being transferred to adjacent carbon skeletons through these alumina nodes, achieving efficient heat transfer between "points (alumina) and surfaces (carbon skeletons)" and further enriching the heat conduction path. Finally, titanate coupling agents were used to treat the filler, improving the poor interfacial affinity between the inorganic filler and the organic polymer (PP) and addressing the issue of numerous voids. This reduced the interfacial thermal resistance, and the surface-modified filler was more uniformly dispersed in the PP, less prone to agglomeration, which is beneficial for forming a more complete thermal conductivity network. The improved interfacial compatibility also indirectly improved the overall performance of the material, enhancing its mechanical properties and impact resistance. Detailed Implementation

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] Example 1: The thermal conductivity enhancer was prepared by the following steps: Step A1: Mix 1g of glucose and 0.3g of tannic acid in 30mL of deionized water and stir until homogeneous. Then add 1.2g of K2FeO4 and 2g of (NH4)2C2O4 and continue stirring for 30min. Then transfer to an oven at 110℃ for pre-foaming for 12h. Then place in a tube furnace and heat-treat at 750℃ under nitrogen for 2h. Cool to room temperature, wash three times with 0.1mol / L dilute hydrochloric acid, then wash with water until neutral, dry, and grind to obtain PGC. Step A2: Disperse 0.5g PGC in a mixture of 80mL ethanol and 20mL deionized water by sonication for 40min, add 0.3g dopamine hydrochloride and stir until homogeneous, adjust the pH to 8.5 with Tris-HCl buffer, stir at room temperature for 24h, filter, wash and dry to obtain PDA@PGC; Step A3: Disperse 0.1g PDA@PGC in 100mL deionized water by ultrasonication for 20min, add 0.3g aluminum nitrate nonahydrate and stir for 40min, then add 6mL of 0.5mol / L ammonia solution and continue stirring for 1h. Filter and wash until the filtrate is free of Al. 3+ Vacuum dried, then placed in a tube furnace and calcined at 600℃ for 2 hours under argon atmosphere to obtain Al2O3@PGC; Step A4: Stir 0.005g of titanate coupling agent OL-T951 in 50mL of toluene until homogeneous, add 1g of Al2O3@PGC and ultrasonically disperse for 0.5h, then heat to 80℃ and stir for 30min. Filter, wash and vacuum dry to obtain the thermal conductivity enhancer.

[0014] Example 2: The thermal conductivity enhancer was prepared by the following steps: Step A1: Mix 1.25g glucose and 0.4g tannic acid in 30mL deionized water and stir until homogeneous. Then add 1.35g K2FeO4 and 2.2g (NH4)2C2O4 and continue stirring for 40min. Then transfer to an oven at 110℃ for pre-foaming for 12h. Then place in a tube furnace and heat-treat at 750℃ under nitrogen for 2h. Cool to room temperature, wash three times with 0.1mol / L dilute hydrochloric acid, then wash with water until neutral, dry, and grind to obtain PGC. Step A2: Disperse 0.5g PGC in a mixture of 80mL ethanol and 20mL deionized water by sonication for 50min, add 0.4g dopamine hydrochloride and stir until homogeneous, adjust the pH to 8.5 with Tris-HCl buffer, stir at room temperature for 24h, filter, wash and dry to obtain PDA@PGC; Step A3: Disperse 0.1g PDA@PGC in 100mL deionized water using ultrasonication for 20min, add 0.4g aluminum nitrate nonahydrate and stir for 50min, then add 8mL of 0.5mol / L ammonia solution and continue stirring for 1h. Filter and wash until the filtrate is free of Al. 3+ Vacuum dried, then placed in a tube furnace and calcined at 600℃ for 2 hours under argon atmosphere to obtain Al2O3@PGC; Step A4: Stir 0.01g of titanate coupling agent OL-T951 in 50mL of toluene until homogeneous, add 1g of Al2O3@PGC and ultrasonically disperse for 45min, then heat to 85℃ and stir for 40min. Filter, wash and vacuum dry to obtain the thermal conductivity enhancer.

[0015] Example 3: The thermal conductivity enhancer was prepared by the following steps: Step A1: Mix 1.5g glucose and 0.5g tannic acid in 30mL deionized water and stir until homogeneous. Then add 1.5g K2FeO4 and 2.5g (NH4)2C2O4 and continue stirring for 50min. Then transfer to an oven at 110℃ for pre-foaming for 12h. Then place in a tube furnace and heat-treat at 750℃ under nitrogen for 2h. Cool to room temperature, wash three times with 0.1mol / L dilute hydrochloric acid, then wash with water until neutral, dry, and grind to obtain PGC. Step A2: Disperse 0.5g PGC in a mixture of 80mL ethanol and 20mL deionized water by sonication for 60min, add 0.5g dopamine hydrochloride and stir until homogeneous, adjust the pH to 8.5 with Tris-HCl buffer, stir at room temperature for 24h, filter, wash and dry to obtain PDA@PGC; Step A3: Disperse 0.1g PDA@PGC in 100mL deionized water by ultrasonication for 20min, add 0.5g aluminum nitrate nonahydrate and stir for 60min, then add 10mL of 0.5mol / L ammonia solution and continue stirring for 1h. Filter and wash until the filtrate is free of Al. 3+ Vacuum dried, then placed in a tube furnace and calcined at 600℃ for 2 hours under argon atmosphere to obtain Al2O3@PGC; Step A4: Stir 0.02g of titanate coupling agent OL-T951 in 50mL of toluene until homogeneous, add 1g of Al2O3@PGC and ultrasonically disperse for 1h, then heat to 90℃ and stir for 50min. Filter, wash and vacuum dry to obtain the thermal conductivity enhancer.

[0016] Example 4: A method for preparing a thermally conductive PP material includes the following steps: 60 parts polypropylene, 15 parts thermal conductivity enhancer prepared in Example 1, 8 parts maleic anhydride grafted polyethylene, 5 parts ethylene-octene copolymer, 0.5 parts antioxidant, and 1 part silicone powder. The raw materials were weighed according to the weight proportions. Polypropylene, the thermal conductivity reinforcing agent prepared in Example 1, maleic anhydride grafted polyethylene, ethylene-octene copolymer, antioxidant, and silicone powder were added to a mixer and mixed evenly. The mixture was then transferred to a twin-screw extruder for extrusion and granulation to obtain the thermally conductive PP material. The temperatures of each section of the twin-screw extruder were as follows: Zone 1 180-200℃, Zone 2 200-210℃, Zone 3 210-220℃, Zone 4 210-220℃, Zone 5 200-210℃, Zone 6 190-210℃, and the die head 200-220℃. The antioxidant included a primary antioxidant and a secondary antioxidant in a 1:1 ratio. The primary antioxidant was antioxidant 1010, and the secondary antioxidant was antioxidant 168.

[0017] Example 5: A method for preparing a thermally conductive PP material includes the following steps: 70 parts polypropylene, 20 parts thermal conductivity enhancer prepared in Example 2, 12 parts maleic anhydride grafted polyethylene, 8 parts ethylene-octene copolymer, 1 part antioxidant, and 1.5 parts polyethylene wax. The raw materials were weighed according to the weight proportions. Polypropylene, the thermal conductivity reinforcing agent prepared in Example 2, maleic anhydride grafted polyethylene, ethylene-octene copolymer, antioxidant, and polyethylene wax were added to a mixer and mixed evenly. The mixture was then transferred to a twin-screw extruder for extrusion and granulation to obtain the thermally conductive PP material. The temperatures of each section of the twin-screw extruder were as follows: Zone 1 180-200℃, Zone 2 200-210℃, Zone 3 210-220℃, Zone 4 210-220℃, Zone 5 200-210℃, Zone 6 190-210℃, and the die head 200-220℃. The antioxidant included a primary antioxidant and a secondary antioxidant, with a ratio of 1:1.5. The primary antioxidant was antioxidant 1076, and the secondary antioxidant was antioxidant 168.

[0018] Example 6: A method for preparing a thermally conductive PP material includes the following steps: 80 parts of polypropylene, 25 parts of the thermal conductivity enhancer prepared in Example 3, 15 parts of maleic anhydride grafted polyethylene, 10 parts of ethylene-octene copolymer, 2 parts of antioxidant, and 2 parts of silicone powder. The raw materials were weighed according to the weight proportions. Polypropylene, the thermal conductivity reinforcing agent prepared in Example 3, maleic anhydride grafted polyethylene, ethylene-octene copolymer, antioxidant, and silicone powder were added to a mixer and mixed evenly. The mixture was then transferred to a twin-screw extruder for extrusion and granulation to obtain the thermally conductive PP material. The temperatures of each section of the twin-screw extruder were as follows: Zone 1 180-200℃, Zone 2 200-210℃, Zone 3 210-220℃, Zone 4 210-220℃, Zone 5 200-210℃, Zone 6 190-210℃, and the die head 200-220℃. The antioxidant included a primary antioxidant and a secondary antioxidant in a ratio of 1:2. The primary antioxidant was antioxidant 1010, and the secondary antioxidant was antioxidant 168.

[0019] Comparative Example 1: This comparative example is a PP material. The difference between this example and Example 6 is that nano-alumina is used instead of the thermal conductivity enhancer prepared in Example 3. All other aspects are the same.

[0020] Comparative Example 2: This comparative example is a PP material. The difference between this example and Example 6 is that the porous graphitized carbon prepared in Example 3 is used instead of the thermal conductivity enhancer prepared in Example 3. All other aspects are the same.

[0021] Comparative Example 3: This comparative example is a PP material, which differs from Example 6 in that carbon nanotubes are used instead of the thermal conductivity enhancer prepared in Example 3.

[0022] The PP materials prepared in Examples 4-6 and Comparative Examples 1-3 were subjected to performance tests: Thermal conductivity test: The PP materials prepared in Examples 4-6 and Comparative Examples 1-3 were made into circular samples with a radius of 50 mm and a thickness of 3 mm. The thermal conductivity of the samples was tested using a Hot Disk thermal constant analyzer of model TPS3500. Impact performance test: The impact performance of the specimens was tested using an impact testing machine. The impact specimens were prepared by a Haake micro injection molding machine and tested at room temperature. The impact energy was 7.5J. The impact strength test was conducted in accordance with GB / T 1043.1-2008 standard. The impact specimen size was 80mm×10mm×4mm. The effective number of test samples was 5, and the average value of the test data was taken. Tensile strength test: The tensile properties of the specimens were tested using a universal tensile testing machine. The dumbbell-shaped specimens were prepared by a Haake micro injection molding machine. The test was conducted at room temperature and at a tensile rate of 5 mm / min, in accordance with the GB / T 1040.2-2006 standard. The tensile specimen size was 75 mm × 4 mm × 2 mm, and the effective number of test samples was 5. The average value of the test data was taken. The test results are shown in Table 1: Table 1: Performance Test Results

[0023] As shown in Table 1, the PP materials prepared in Examples 4-6 of this invention exhibit excellent thermal conductivity, with thermal conductivity ranging from 1.33 to 1.41 W / m·K after thermal conductivity testing. After impact performance testing, the impact strength was within the range of 7.2-7.5 kJ / m. 2Within the range, the impact performance is improved. This is because there is a strong interfacial bond and good dispersibility between the internal thermal conductivity enhancer and the matrix, thus improving the impact resistance of the material. After tensile strength testing, the tensile strength is in the range of (23.7-24.5) MPa. Compared with the material prepared in the comparative example, it has better tensile strength. This is because the thermal conductivity enhancer has good dispersibility between the matrix and the material prepared in Examples 4-6.

[0024] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A thermally conductive PP material, characterized in that, The raw materials include the following parts by weight: 60-80 parts polypropylene, 15-25 parts thermal conductivity enhancer, 8-15 parts maleic anhydride grafted polyethylene, 5-10 parts ethylene-octene copolymer, 0.5-2 parts antioxidant, and 1-2 parts lubricant. The thermal conductivity enhancer is Al2O3@PGC obtained by treating it with a titanate coupling agent; Al2O3@PGC is obtained by loading aluminum ions onto PDA@PGC and then calcining it at high temperature; PDA@PGC is obtained by polymerizing dopamine hydrochloride as a monomer to form a polydopamine layer on the surface of PGC; PGC is obtained by using glucose and tannic acid as carbon sources, adding K2FeO4 and (NH4)2C2O4 for pre-foaming, and then calcining it at high temperature.

2. The thermally conductive PP material according to claim 1, characterized in that, The thermal conductivity enhancer is prepared by the following steps: Step A1: Mix glucose and tannic acid in deionized water and stir until homogeneous. Then add K2FeO4 and (NH4)2C2O4 and continue stirring for 30-50 minutes. Then transfer to an oven at 110℃ for pre-foaming for 12 hours. Then place in a tube furnace and heat-treat at 750℃ under nitrogen for 2 hours. Cool to room temperature, wash three times with 0.1mol / L dilute hydrochloric acid, then wash with water until neutral, dry, and grind to obtain PGC. Step A2: Disperse PGC in a mixture of ethanol and deionized water by sonication for 40-60 min, add dopamine hydrochloride and stir until homogeneous, adjust the pH to 8.5 with Tris-HCl buffer, stir at room temperature for 24 h, filter, wash and dry to obtain PDA@PGC; Step A3: Disperse PDA@PGC in deionized water using ultrasound for 20 min, add aluminum nitrate nonahydrate and stir for 40-60 min, then add 0.5 mol / L ammonia solution dropwise and continue stirring for 1 h. Filter and wash until the filtrate is free of Al. 3+ Vacuum dried, then placed in a tube furnace and calcined at 600℃ for 2 hours under argon atmosphere to obtain Al2O3@PGC; Step A4: Stir the titanate coupling agent OL-T951 in toluene until homogeneous, add Al2O3@PGC and ultrasonically disperse for 0.5-1 h, then heat to 80-90℃ and stir for 30-50 min. Filter, wash and vacuum dry to obtain the thermal conductivity enhancer.

3. The thermally conductive PP material according to claim 2, characterized in that, In step A1, the ratio of glucose, tannic acid, deionized water, K2FeO4 and (NH4)2C2O4 is 1-1.5g:0.3-0.5g:30mL:1.2-1.5g:2-2.5g.

4. The thermally conductive PP material according to claim 2, characterized in that, In step A2, the ratio of PGC, ethanol, deionized water and dopamine hydrochloride is 0.5g:80mL:20mL:0.3-0.5g.

5. The thermally conductive PP material according to claim 2, characterized in that, In step A3, the ratio of PDA@PGC, deionized water, aluminum nitrate nonahydrate, and ammonia is 0.1g:100mL:0.3-0.5g:6-10mL.

6. The thermally conductive PP material according to claim 2, characterized in that, In step A4, the ratio of titanate coupling agent OL-T951, toluene, and Al2O3@PGC is 0.005-0.02g:50mL:1g.

7. The thermally conductive PP material according to claim 1, characterized in that, The antioxidant includes a primary antioxidant and a secondary antioxidant, and the ratio of the two is 1:1-2. The primary antioxidant is antioxidant 1010 or antioxidant 1076, and the secondary antioxidant is antioxidant 168.

8. The thermally conductive PP material according to claim 1, characterized in that, The lubricant is either silicone powder or polyethylene wax.

9. A method for preparing the thermally conductive PP material according to any one of claims 1-8, characterized in that, Includes the following steps: Weigh the raw materials according to the weight parts, add polypropylene, thermal conductivity enhancer, maleic anhydride grafted polyethylene, ethylene-octene copolymer, antioxidant and lubricant into a mixer and mix evenly, then transfer to a twin-screw extruder for extrusion granulation to obtain thermally conductive PP material.

10. A method for preparing a thermally conductive PP material according to claim 9, characterized in that, The temperatures of each section of the twin-screw extruder are as follows: Zone 1 180-200℃, Zone 2 200-210℃, Zone 3 210-220℃, Zone 4 210-220℃, Zone 5 200-210℃, Zone 6 190-210℃, and Die head 200-220℃.

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