Polypropylene composite and method of manufacture

Abstract

The application provides a polypropylene composite material and a preparation method. The polypropylene composite material comprises, in mass parts, 55-70 parts of homopolymer polypropylene, 10-25 parts of short glass fiber, 10-20 parts of rice husk carbon powder, 0.2-0.5 parts of alpha nucleating agent, 0.3-0.6 parts of antioxidant, 0.5-1.0 parts of silane coupling agent and 0.2-0.5 parts of processing aid. The polypropylene composite material in the above scheme solves the technical problem that the modification method of the polypropylene in the prior art is insufficient in improving the heat resistance of the polypropylene and affects the processing fluidity.

Description

Technical Field

[0001] This invention relates to the technical field of polypropylene modification, and more specifically, to a polypropylene composite material and its preparation method. Background Technology

[0002] Polypropylene (PP), as a general-purpose thermoplastic, is widely used in the automotive parts industry due to its advantages such as low density, excellent mechanical properties, good processing flowability, and low cost. However, conventional polypropylene has limited heat resistance, with a heat distortion temperature of approximately 75℃ and a long-term service temperature not exceeding 90℃. In high-temperature environments, it is prone to softening, creep, and deformation, leading to decreased dimensional stability and shortened service life, making it unsuitable for the automotive operating conditions in regions with strong sunlight and high temperatures, such as Saudi Arabia and Africa.

[0003] To improve the heat resistance of polypropylene, existing technologies mainly employ methods such as copolymerization modification, nucleating agent addition, filler filling, or crosslinking treatment. Among these, copolymerization modification and nucleating agent modification have limited effects on improving heat resistance, typically increasing the heat distortion temperature by only about 10°C. While crosslinking modification can significantly improve heat resistance, it drastically reduces the processing fluidity of polypropylene, increasing the difficulty of recycling.

[0004] There is currently no effective solution to the technical problems that existing modification methods for polypropylene cannot adequately improve its heat resistance and affect its processing fluidity. Summary of the Invention

[0005] The main objective of this invention is to provide a polypropylene composite material and its preparation method, so as to solve the technical problems of insufficient improvement of heat resistance and impact on processing fluidity of polypropylene by existing modification methods.

[0006] To achieve the above objectives, according to one aspect of the present invention, a polypropylene composite material is provided, comprising, by weight: 55-70 parts of homopolymer polypropylene, 10-25 parts of short glass fibers, 10-20 parts of rice husk charcoal powder, 0.2-0.5 parts of α-nucleating agent, 0.3-0.6 parts of antioxidant, 0.5-1.0 parts of silane coupling agent, and 0.2-0.5 parts of processing aid.

[0007] Furthermore, the isotacticity of homopolymer polypropylene is greater than or equal to 98%, and the melt index of homopolymer polypropylene is 10~20 g / 10 min.

[0008] Furthermore, the short glass fibers have a diameter of 10~13μm and a length of 3~5mm.

[0009] Furthermore, the particle size of rice husk charcoal powder is 400-600 mesh.

[0010] Furthermore, the α-nucleating agent is a sorbitol-based nucleating agent or an organophosphate nucleating agent, preferably a dibenzyl sorbitol.

[0011] Furthermore, the antioxidant includes a primary antioxidant and a secondary antioxidant. The primary antioxidant is a hindered phenolic antioxidant, and the secondary antioxidant is a phosphite antioxidant. The mass ratio of the primary antioxidant to the secondary antioxidant is 1:2.

[0012] Furthermore, the processing aid is calcium stearate or zinc stearate.

[0013] According to another aspect of the present invention, a method for preparing the above-mentioned polypropylene composite material is provided, the method comprising the following steps: step S1, mixing a first raw material comprising homopolymer polypropylene, α-nucleating agent, antioxidant and processing aid to obtain a first mixture; step S2, adding a second raw material comprising short glass fiber, rice husk carbon powder and silane coupling agent to the first mixture for mixing to obtain a second mixture; step S3, feeding the second mixture into an extruder, melt-extruding and granulating and drying to obtain the polypropylene composite material.

[0014] Further, in step S3, the extruder includes a feeding section, a plasticizing section, a homogenizing section, and a die head section. The set temperature of the feeding section is 180~190℃, the set temperature of the plasticizing section is 200~220℃, the set temperature of the homogenizing section is 210~230℃, and the set temperature of the die head section is 220~240℃.

[0015] Furthermore, in step S1, the mixing temperature of the first raw material is 80~90℃, the mixing speed is 800~1000r / min, and the mixing time is 5~8min.

[0016] By applying the technical solution of this invention, short glass fibers possess extremely high modulus and tensile strength. Dispersed within homopolymer polypropylene, these short glass fibers provide the composite material with flexural strength and flexural modulus, effectively suppressing creep and deformation of the homopolymer polypropylene. Rice husk charcoal powder, with its high silica and carbon skeleton content, forms a thermal barrier within the homopolymer polypropylene, effectively preventing heat conduction into the material and delaying softening. Simultaneous filling of short glass fibers and rice husk charcoal powder within the homopolymer polypropylene provides the main load-bearing skeleton, while the rice husk charcoal powder fills voids, suppresses thermal motion, and disperses stress. In other words, the rice husk charcoal powder and short glass fibers form a spatial network interlocking, generating a dual-channel synergistic reinforcement effect within the homopolymer polypropylene. This achieves a simultaneous leap in rigidity and heat resistance without sacrificing processing performance, solving the technical problems of insufficient heat resistance improvement and reduced processing fluidity associated with existing polypropylene modification methods. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 A schematic diagram of the preparation process of the polypropylene composite material in this invention is shown. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that the disclosure of this application is thorough and complete, and that the concept of these exemplary embodiments is fully conveyed to those skilled in the art. In the drawings, for clarity, the thickness of layers and regions may be exaggerated, and the same reference numerals are used to denote the same devices, and therefore their description will be omitted.

[0023] As analyzed in the background section, existing technologies have technical problems such as insufficient improvement of the heat resistance of polypropylene by modification methods, and impact on processing fluidity. To solve this problem, the present invention provides a polypropylene composite material and its preparation method.

[0024] In one typical embodiment of this application, a polypropylene composite material is provided, comprising, by weight: 55-70 parts of homopolymer polypropylene, 10-25 parts of short glass fibers, 10-20 parts of rice husk charcoal powder, 0.2-0.5 parts of α-nucleating agent, 0.3-0.6 parts of antioxidant, 0.5-1.0 parts of silane coupling agent, and 0.2-0.5 parts of processing aid.

[0025] In the embodiments of this application, short glass fibers have extremely high modulus and tensile strength. The short glass fibers dispersed in homopolymer polypropylene can provide the flexural strength and flexural modulus of the composite material, effectively suppressing the creep and deformation of the homopolymer polypropylene. Rice husk charcoal powder has a high content of silica and carbon skeleton, which can form a thermal barrier in the homopolymer polypropylene, effectively blocking heat conduction to the interior of the material, thereby delaying the softening of the homopolymer polypropylene. The homopolymer polypropylene is simultaneously filled with short glass fibers and rice husk charcoal powder. The short glass fibers provide the main load-bearing skeleton, while the rice husk charcoal powder fills the voids, suppresses thermal motion, and disperses stress. That is, the rice husk charcoal powder and short glass fibers form a spatial network interlocking. The two produce a dual-channel synergistic reinforcement effect in the homopolymer polypropylene, achieving a simultaneous leap in rigidity and heat resistance without sacrificing processing performance. This solves the technical problems of insufficient improvement of heat resistance and impact on processing fluidity of polypropylene by modification methods in the prior art.

[0026] It should be noted that the short glass fiber surface is pretreated with a silane coupling agent. The pretreated short glass fiber can improve the interfacial bonding with homopolymer polypropylene and avoid performance degradation caused by interfacial defects. The rice husk carbon powder is pyrolyzed under anaerobic or anaerobic conditions to remove impurities and organic components, thereby increasing the carbon and silicon content. The rough surface and reduced surface hydrophilic groups help it to bond with homopolymer polypropylene and form a synergistic reinforcing effect with the short glass fiber, further improving the heat resistance and dimensional stability of the material, while reducing the material cost.

[0027] In one embodiment of this application, the isotacticity of the homopolymer polypropylene is greater than or equal to 98%, and the melt index of the homopolymer polypropylene is 10~20g / 10min.

[0028] In the embodiments of this application, the propylene monomers of the highly regular homopolymer polypropylene are mostly arranged in the same spatial orientation during polymerization, forming a highly ordered crystalline structure. This means the molecular chains are tightly locked within the crystalline regions, hindering thermal motion and increasing the relaxation temperature of the molecular chain segments, which helps to improve the heat distortion temperature of the composite material. The melt flow index reflects the fluidity of the homopolymer polypropylene in the molten state. A melt flow index of 10~20 g / 10min can achieve a balance between rheological and mechanical properties, allowing the silane coupling agent to fully react with the surface of short glass fibers and rice husk powder during the melting process, achieving strong interfacial bonding and avoiding inhibition of coupling agent diffusion due to excessively high viscosity. Selecting homopolymer polypropylene with high regularity and a suitable melt flow index allows for precise control of the molecular structure and rheological properties of the matrix material, improving the crystallinity, stiffness, and processing performance of the composite material.

[0029] In one embodiment of this application, the short glass fiber has a diameter of 10~13μm and a length of 3~5mm.

[0030] In the embodiments of this application, the diameter of the short glass fibers ranges from 10 to 13 μm and the length ranges from 3 to 5 mm. The short glass fibers within this range maintain sufficient rigidity while possessing good flexibility and deformability, and can be uniformly dispersed in homopolymer polypropylene to avoid agglomeration or floating.

[0031] For example, the diameter of the short glass fiber can be any one or more of 10μm, 11μm, 12μm and 13μm, and the length of the short glass fiber can be any one or more of 3mm, 4mm and 5mm.

[0032] In one embodiment of this application, the particle size of the rice husk charcoal powder is 400-600 mesh.

[0033] In the embodiments of this application, the rice husk charcoal powder is at the micron-level filling scale to fill the pores of short glass fibers. The particle size range of the rice husk charcoal powder is selected as 400~600 mesh. The rice husk charcoal powder can not only be uniformly dispersed in the gaps of the short glass fiber network, but also has good fluidity, which can be uniformly mixed with other components to avoid agglomeration or floating.

[0034] For example, the particle size of rice husk charcoal powder can be any one or more of 400 mesh, 450 mesh, 500 mesh, 550 mesh and 600 mesh.

[0035] In one embodiment of this application, the α-nucleating agent is a sorbitol-based nucleating agent or an organophosphate nucleating agent, preferably a dibenzyl sorbitol.

[0036] In the embodiments of this application, α-nucleating agents are used to induce the rapid formation of a large number of fine and uniform α-nuclei in homopolymer polypropylene during melt cooling, thereby increasing the crystallization temperature, accelerating the crystallization rate, refining the spherulite size, and thus improving the heat resistance and rigidity of the composite material, while also improving the transparency of the composite material. Dibenzyl sorbitol, as a highly efficient α-nucleating agent, has a highly symmetrical rigid framework in its molecular structure, which can form nanoscale nucleation sites in the polypropylene melt, increasing the nucleus density by tens or even hundreds of times. The final grain size can be reduced from hundreds of nanometers to tens of nanometers. This extreme refinement of grains means a dramatic increase in the number of grain boundaries per unit volume. As a barrier to molecular chain movement, grain boundaries can more effectively constrain the thermal movement of polypropylene segments at high temperatures, thereby directly increasing the heat distortion temperature.

[0037] In one embodiment of this application, the antioxidant includes a primary antioxidant and a secondary antioxidant. The primary antioxidant is a hindered phenolic antioxidant, and the secondary antioxidant is a phosphite antioxidant. The mass ratio of the primary antioxidant to the secondary antioxidant is 1:2.

[0038] In the embodiments of this application, hindered phenolic antioxidants are selected as the main antioxidants and phosphite antioxidants are selected as auxiliary antioxidants. The main antioxidants and auxiliary antioxidants are mixed in a mass ratio of 1:2 to form an antioxidant system, which can inhibit the thermo-oxidative degradation of homopolymer polypropylene during processing and use, and extend the high-temperature service life of the material.

[0039] Furthermore, the primary antioxidant is preferably antioxidant 1010, and the secondary antioxidant is preferably antioxidant 168.

[0040] In one embodiment of this application, the processing aid is calcium stearate or zinc stearate.

[0041] In the embodiments of this application, the processing aid is calcium stearate or zinc stearate, which is used to improve the processing fluidity of the composite material, reduce the wear of equipment during processing, and avoid problems such as yellowing and degradation of the composite material.

[0042] In one embodiment of this application, the silane coupling agent is γ-aminopropyltriethoxysilane (KH-550), which is used to improve the interfacial compatibility of short glass fiber, rice husk carbon powder and homopolymer polypropylene, enhance the bonding force between the filler and homopolymer polypropylene, and improve the stiffness and heat resistance stability of the composite material.

[0043] In another typical embodiment of this application, a method for preparing the aforementioned polypropylene composite material is provided, such as... Figure 1 As shown, the preparation method includes the following steps:

[0044] Step S1: Mix the first raw material, which includes homopolymer polypropylene, α-nucleating agent, antioxidant and processing aid, to obtain a first mixture.

[0045] Step S2: The second raw material, including short glass fiber, rice husk carbon powder and silane coupling agent, is added to the first mixture and mixed to obtain the second mixture.

[0046] Step S3: The second mixture is fed into an extruder, melt-extruded and granulated, and then dried to obtain a polypropylene composite material.

[0047] In the embodiments of this application, the homopolymer polypropylene, α-nucleating agent, antioxidant, and processing aid are all fine particles or low-melting-point organic materials with small particle size, good flowability, and high compatibility with homopolymer polypropylene. They can quickly achieve molecular-level uniform dispersion in high-speed mixing to form a matrix premix system. In this matrix premix system, the α-nucleating agent is uniformly distributed between polypropylene molecular chains, the antioxidant forms a protective layer, and the processing aid lubricates the matrix surface, creating an environment for the subsequent introduction of high-content fillers and greatly reducing the risk of uneven dispersion caused by excessively high local concentrations after the fillers are added. The second raw material, comprising short glass fibers, rice husk carbon powder, and silane coupling agent, is added to the first mixture for mixing. This allows the silane coupling agent, in a state where the homopolymer polypropylene is initially dispersed and has a suitable viscosity, to preferentially undergo hydrolysis and condensation reactions with the hydroxyl and siloxane groups on the surface of the short glass fibers and rice husk carbon powder, forming a chemical anchoring layer. This significantly improves the utilization rate of the silane coupling agent, ensuring that the surface of each short glass fiber and each rice husk carbon powder particle is effectively modified, forming a strong interfacial bond between the rice husk carbon powder, the silane coupling agent, and the homopolymer polypropylene, thus significantly improving stress transfer efficiency.

[0048] Further, in step S3, the extruder includes a feeding section, a plasticizing section, a homogenizing section, and a die head section. The set temperature of the feeding section is 180~190℃, the set temperature of the plasticizing section is 200~220℃, the set temperature of the homogenizing section is 210~230℃, and the set temperature of the die head section is 220~240℃.

[0049] In the embodiments of this application, the temperature of each operating section of the extruder is controlled within the above-mentioned range. Under the premise of ensuring that each component is fully melted, uniformly dispersed, and effectively bonded at the interface, thermal degradation, carbonization, and dispersion failure are avoided to the greatest extent, thereby achieving microscopic control of mixing uniformity.

[0050] It should be noted that the set temperature of the feeding section is 180~190℃. The material in this section is a solid mixture, including unmelted homopolymer polypropylene, short glass fiber, rice husk charcoal powder, silane coupling agent, etc. This ensures that the material enters the screw smoothly and leaves a buffer space for full plasticization in the subsequent temperature zone, avoiding the filler being forcibly sheared before it is fully wetted, which would cause the short glass fiber to break or the rice husk charcoal powder to agglomerate.

[0051] The plasticizing section is set at a temperature of 200~220℃. Homopolymer polypropylene melts completely within this temperature range, and the viscosity reaches a moderate level, providing a rheological environment for the high-shear screw. The silane coupling agent begins to fully hydrolyze above 200℃, and its ethoxy groups undergo a condensation reaction with the hydroxyl groups on the surface of rice husk charcoal powder and short glass fibers to form a chemical anchoring layer. Within this temperature range, the carbon-silicon structure of the rice husk charcoal powder is stable, with no risk of secondary carbonization or oxidation. The silane coating on the surface of the glass fibers is also not damaged, laying a chemical foundation for the uniform distribution in the subsequent homogenization section.

[0052] The homogenization zone is set at a temperature of 210~230℃. By further increasing the temperature, the melt viscosity is reduced, the molecular chain mobility is enhanced, and the final wetting and encapsulation of the paired residual micro-regions is achieved. At the same time, a slight increase in temperature can activate the activity of the residual coupling agent, realize the replacement reaction, and ensure that every filler and homopolymer polypropylene interface is fully modified. The temperature in this zone is still below the degradation threshold of homopolymer polypropylene, avoiding oxidation chain scission, yellowing, or the generation of small molecule volatiles caused by excessive temperature.

[0053] The set temperature of the die head section is 220~240℃ to ensure that the melt maintains a low viscosity and high fluidity state before entering the pelletizer. This allows the melt, which has been carefully homogenized in all the previous temperature zones, to be output stably in the form of a homogeneous fluid, avoiding localized filler enrichment or filler sedimentation caused by uneven shearing at the outlet. This ensures that the uniformity at the microscopic level is completely preserved in the final product.

[0054] Furthermore, in step S1, the mixing temperature of the first raw material is 80~90℃, the mixing speed is 800~1000r / min, and the mixing time is 5~8min.

[0055] In the embodiments of this application, controlling the mixing temperature, mixing speed and mixing time of the first raw material within the above range helps to fully disperse and mix the first raw material.

[0056] Example 1

[0057] Weigh the following components by weight percentage:

[0058] Weigh 65 wt% of homopolymer polypropylene, with an isotacticity of 98% and a melt index of 15 g / 10 min; weigh 18 wt% of short glass fibers, with a diameter of 11 μm and a length of 4 mm, wherein the short glass fibers are pretreated with silane; weigh 15 wt% of rice husk carbon powder, which has a 500-mesh sheet structure; weigh 0.3 wt% of α-nucleating agent, wherein dibenzyl sorbitol is selected as the α-nucleating agent; weigh 0.2 wt% of antioxidant 1010 and 0.4 wt% of antioxidant 168; weigh 0.7 wt% of silane coupling agent; weigh 0.4 wt% of calcium stearate.

[0059] The homopolymer polypropylene, dibenzyl sorbitol, antioxidant 1010, antioxidant 168 and calcium stearate in the above components were placed in a high-speed mixer. The mixing temperature was 85℃, the mixing speed was 900r / min, and the mixing time was 5min to obtain the first mixture.

[0060] Add short glass fibers, rice husk carbon powder, and silane coupling agent to the first mixture, and continue mixing for 4 minutes to ensure uniform dispersion, to obtain the second mixture;

[0061] The second mixture is fed into a twin-screw extruder. The temperature of the feeding section is set to 185℃, the temperature of the plasticizing section is set to 210℃, the temperature of the homogenizing section is set to 220℃, the temperature of the die head section is set to 230℃, and the screw speed is 250 r / min. Melt extrusion granulation is performed. After the extruded granules are dried at 90℃ for 2.5 h, polypropylene composite material is obtained.

[0062] Example 2

[0063] Weigh 60 wt% of homopolymer polypropylene, with an isotacticity of 98.5% and a melt index of 12 g / 10 min; weigh 20 wt% of short glass fibers, with a diameter of 10 μm and a length of 3 mm, wherein the short glass fibers are pretreated with silane; weigh 18 wt% of rice husk carbon powder, which has a 600-mesh sheet structure; weigh 0.4 wt% of α-nucleating agent, wherein dibenzyl sorbitol is selected as the α-nucleating agent; weigh 0.2 wt% of antioxidant 1010 and 0.4 wt% of antioxidant 168; weigh 0.8 wt% of silane coupling agent; weigh 0.2 wt% of calcium stearate.

[0064] The homopolymer polypropylene, dibenzyl sorbitol, antioxidant 1010, antioxidant 168 and calcium stearate in the above components were placed in a high-speed mixer. The mixing temperature was 80℃, the mixing speed was 800r / min, and the mixing time was 8min to obtain the first mixture.

[0065] Add short glass fibers, rice husk carbon powder, and silane coupling agent to the first mixture, and continue mixing for 5 minutes to ensure uniform dispersion, thus obtaining the second mixture.

[0066] The second mixture is fed into a twin-screw extruder. The temperature of the feeding section is set to 180℃, the temperature of the plasticizing section is set to 200℃, the temperature of the homogenizing section is set to 210℃, the temperature of the die head section is set to 220℃, and the screw speed is 200 r / min. Melt extrusion granulation is performed. After the extruded granules are dried at 90℃ for 2.5 h, polypropylene composite material is obtained.

[0067] Example 3

[0068] Weigh 68 wt% of homopolymer polypropylene, with an isotacticity of 98% and a melt index of 18 g / 10 min; weigh 20 wt% of short glass fibers, with a diameter of 13 μm and a length of 5 mm, wherein the short glass fibers are pretreated with silane; weigh 10 wt% of rice husk carbon powder, which has a 450-mesh sheet structure; weigh 0.2 wt% of α-nucleating agent, wherein dibenzyl sorbitol is selected as the α-nucleating agent; weigh 0.1 wt% of antioxidant 1010 and 0.2 wt% of antioxidant 168; weigh 1 wt% of silane coupling agent; and weigh 0.5 wt% of calcium stearate.

[0069] The homopolymer polypropylene, dibenzyl sorbitol, antioxidant 1010, antioxidant 168 and calcium stearate in the above components were placed in a high-speed mixer. The mixing temperature was 90℃, the mixing speed was 1000r / min, and the mixing time was 5min to obtain the first mixture.

[0070] Add short glass fibers, rice husk carbon powder, and silane coupling agent to the first mixture, and continue mixing for 3 minutes to ensure uniform dispersion, thus obtaining the second mixture.

[0071] The second mixture is fed into a twin-screw extruder. The temperature of the feeding section is set to 190℃, the temperature of the plasticizing section is set to 220℃, the temperature of the homogenizing section is set to 230℃, the temperature of the die head section is set to 240℃, and the screw speed is 300 r / min. Melt extrusion granulation is performed. After the extruded granules are dried at 100℃ for 2 hours, polypropylene composite material is obtained.

[0072] Example 4

[0073] Weigh the following components by weight percentage:

[0074] Weigh 55 wt% of homopolymer polypropylene, with an isotacticity of 98% and a melt index of 15 g / 10 min; weigh 23 wt% of short glass fibers, with a diameter of 11 μm and a length of 4 mm, wherein the short glass fibers are pretreated with silane; weigh 20 wt% of rice husk carbon powder, which has a 500-mesh sheet structure; weigh 0.3 wt% of α-nucleating agent, wherein dibenzyl sorbitol is selected as the α-nucleating agent; weigh 0.2 wt% of antioxidant 1010 and 0.4 wt% of antioxidant 168; weigh 0.7 wt% of silane coupling agent; weigh 0.4 wt% of calcium stearate.

[0075] The homopolymer polypropylene, dibenzyl sorbitol, antioxidant 1010, antioxidant 168 and calcium stearate in the above components were placed in a high-speed mixer. The mixing temperature was 85℃, the mixing speed was 900r / min, and the mixing time was 5min to obtain the first mixture.

[0076] Add short glass fibers, rice husk carbon powder, and silane coupling agent to the first mixture, and continue mixing for 4 minutes to ensure uniform dispersion, to obtain the second mixture;

[0077] The second mixture is fed into a twin-screw extruder. The temperature of the feeding section is set to 185℃, the temperature of the plasticizing section is set to 210℃, the temperature of the homogenizing section is set to 220℃, the temperature of the die head section is set to 230℃, and the screw speed is 250 r / min. Melt extrusion granulation is performed. After the extruded granules are dried at 90℃ for 2.5 h, polypropylene composite material is obtained.

[0078] Example 5

[0079] Weigh the following components by weight percentage:

[0080] Weigh 55 wt% of homopolymer polypropylene, with an isotacticity of 98% and a melt index of 15 g / 10 min; weigh 25 wt% of short glass fibers, with a diameter of 11 μm and a length of 4 mm, wherein the short glass fibers are pretreated with silane; weigh 18 wt% of rice husk carbon powder, which has a 500-mesh sheet structure; weigh 0.3 wt% of α-nucleating agent, wherein dibenzyl sorbitol is selected as the α-nucleating agent; weigh 0.2 wt% of antioxidant 1010 and 0.4 wt% of antioxidant 168; weigh 0.7 wt% of silane coupling agent; weigh 0.4 wt% of calcium stearate.

[0081] The homopolymer polypropylene, dibenzyl sorbitol, antioxidant 1010, antioxidant 168 and calcium stearate in the above components were placed in a high-speed mixer. The mixing temperature was 85℃, the mixing speed was 900r / min, and the mixing time was 5min to obtain the first mixture.

[0082] Add short glass fibers, rice husk carbon powder, and silane coupling agent to the first mixture, and continue mixing for 4 minutes to ensure uniform dispersion, to obtain the second mixture;

[0083] The second mixture is fed into a twin-screw extruder. The temperature of the feeding section is set to 185℃, the temperature of the plasticizing section is set to 210℃, the temperature of the homogenizing section is set to 220℃, the temperature of the die head section is set to 230℃, and the screw speed is 250 r / min. Melt extrusion granulation is performed. After the extruded granules are dried at 90℃ for 2.5 h, polypropylene composite material is obtained.

[0084] Example 6

[0085] Weigh the following components by weight percentage:

[0086] Weigh 70 wt% of homopolymer polypropylene, with an isotacticity of 98% and a melt index of 15 g / 10 min; weigh 10 wt% of short glass fibers, with a diameter of 11 μm and a length of 4 mm, wherein the short glass fibers are pretreated with silane; weigh 18 wt% of rice husk carbon powder, which has a 500-mesh sheet structure; weigh 0.3 wt% of α-nucleating agent, wherein dibenzyl sorbitol is selected as the α-nucleating agent; weigh 0.2 wt% of antioxidant 1010 and 0.4 wt% of antioxidant 168; weigh 0.7 wt% of silane coupling agent; weigh 0.4 wt% of calcium stearate.

[0087] The homopolymer polypropylene, dibenzyl sorbitol, antioxidant 1010, antioxidant 168 and calcium stearate in the above components were placed in a high-speed mixer. The mixing temperature was 85℃, the mixing speed was 900r / min, and the mixing time was 5min to obtain the first mixture.

[0088] Add short glass fibers, rice husk carbon powder, and silane coupling agent to the first mixture, and continue mixing for 4 minutes to ensure uniform dispersion, to obtain the second mixture;

[0089] The second mixture is fed into a twin-screw extruder. The temperature of the feeding section is set to 185℃, the temperature of the plasticizing section is set to 210℃, the temperature of the homogenizing section is set to 220℃, the temperature of the die head section is set to 230℃, and the screw speed is 250 r / min. Melt extrusion granulation is performed. After the extruded granules are dried at 90℃ for 2.5 h, polypropylene composite material is obtained.

[0090] Comparative Example 1

[0091] Weigh out 79 wt% homopolymer polypropylene, 20 wt% short glass fiber, 0.1 wt% antioxidant 1010, 0.2 wt% antioxidant 168, 0.2 wt% calcium stearate, 0.5 wt% silane coupling agent, and no rice husk carbon powder or α-nucleating agent.

[0092] The homopolymer polypropylene, antioxidant 1010, antioxidant 168 and calcium stearate in the above components were placed in a high-speed mixer. The mixing temperature was 85°C, the mixing speed was 900 r / min, and the mixing time was 5 min to obtain the first mixture.

[0093] Add short glass fibers and silane coupling agent to the first mixture, and continue mixing for 4 minutes to ensure uniform dispersion, to obtain the second mixture;

[0094] The second mixture is fed into a twin-screw extruder. The temperature of the feeding section is set to 185℃, the temperature of the plasticizing section is set to 210℃, the temperature of the homogenizing section is set to 220℃, the temperature of the die head section is set to 230℃, and the screw speed is 250 r / min. Melt extrusion granulation is performed. After the extruded granules are dried at 90℃ for 2.5 h, polypropylene composite material is obtained.

[0095] Comparative Example 2

[0096] Weigh out 79 wt% homopolymer polypropylene, 20 wt% rice husk charcoal powder, 0.1 wt% antioxidant 1010, 0.2 wt% antioxidant 168, 0.2 wt% calcium stearate, 0.5 wt% silane coupling agent, without short glass fibers and α-nucleating agent.

[0097] The homopolymer polypropylene, antioxidant 1010, antioxidant 168 and calcium stearate in the above components were placed in a high-speed mixer. The mixing temperature was 85°C, the mixing speed was 900 r / min, and the mixing time was 5 min to obtain the first mixture.

[0098] Add rice husk charcoal powder and silane coupling agent to the first mixture, and continue mixing for 4 minutes to ensure uniform dispersion, to obtain the second mixture;

[0099] The second mixture is fed into a twin-screw extruder. The temperature of the feeding section is set to 185℃, the temperature of the plasticizing section is set to 210℃, the temperature of the homogenizing section is set to 220℃, the temperature of the die head section is set to 230℃, and the screw speed is 250 r / min. Melt extrusion granulation is performed. After the extruded granules are dried at 90℃ for 2.5 h, polypropylene composite material is obtained.

[0100] The polypropylene composite materials obtained in Examples 1 to 6, the polypropylene composite material obtained in Comparative Example 1, and the polypropylene composite material obtained in Comparative Example 2 were prepared into specimens, and the obtained specimens were subjected to heat deformation test and bending test. The test results are listed in Table 1.

[0101] Table 1

[0102]

[0103] Comparative test results show that the heat distortion temperature, flexural strength, and flexural modulus of the polypropylene composite materials in Examples 1 to 6 of this application are all higher than those in the comparative example, proving that the component ratio and process optimization in this application can effectively improve the heat resistance and deformation resistance of polypropylene, and solve the shortcomings of the prior art.

[0104] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0105] 1. By using short glass fibers and rice husk carbon powder for synergistic reinforcement, combined with the crystallization optimization effect of α-nucleating agents, the heat resistance and mechanical properties are synergistically improved, breaking through the bottleneck of insufficient heat resistance improvement by single filler modification.

[0106] 2. Anaerobic or hypoxic pyrolysis improves the interfacial bonding between rice husk charcoal powder and homopolymer polypropylene. Combustion increases the carbon and silicon content, improving the stiffness of the filler. Silane coupling agent improves the interfacial compatibility between the filler and the polypropylene matrix, solving problems such as decreased toughness and interfacial defects caused by filler modification, and improving heat resistance and deformation resistance.

[0107] 3. Biomass filler is used, and the interfacial bonding strength between biomass and homopolymer polypropylene is improved. Short glass fibers are added simultaneously, and the component ratio and processing technology are optimized. While ensuring high heat resistance, the material has good processing fluidity, reducing production costs and facilitating industrial-scale production.

[0108] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0109] In addition to the above, it should be noted that the terms "one embodiment," "another embodiment," and "embodiment" used in this specification refer to specific features, structures, or characteristics described in connection with that embodiment, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this invention.

[0110] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0111] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polypropylene composite material, characterized in that, The polypropylene composite material comprises, by weight, 55-70 parts of homopolymer polypropylene, 10-25 parts of short glass fiber, 10-20 parts of rice husk charcoal powder, 0.2-0.5 parts of α-nucleating agent, 0.3-0.6 parts of antioxidant, 0.5-1.0 parts of silane coupling agent, and 0.2-0.5 parts of processing aid.

2. The polypropylene composite material according to claim 1, characterized in that, The isotacticity of the homopolymer polypropylene is greater than or equal to 98%, and the melt index of the homopolymer polypropylene is 10~20 g / 10 min.

3. The polypropylene composite material according to claim 1, characterized in that, The short glass fibers have a diameter of 10~13μm and a length of 3~5mm.

4. The polypropylene composite material according to claim 1, characterized in that, The particle size of the rice husk charcoal powder is 400-600 mesh.

5. The polypropylene composite material according to claim 1, characterized in that, The α-nucleating agent is a sorbitol-based nucleating agent or an organophosphate nucleating agent, preferably a dibenzyl sorbitol.

6. The polypropylene composite material according to claim 1, characterized in that, The antioxidant includes a primary antioxidant and a secondary antioxidant. The primary antioxidant is a hindered phenolic antioxidant, and the secondary antioxidant is a phosphite antioxidant. The mass ratio of the primary antioxidant to the secondary antioxidant is 1:

2.

7. The polypropylene composite material according to claim 1, characterized in that, The processing aid is calcium stearate or zinc stearate.

8. A method for preparing the polypropylene composite material according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: Step S1: Mix the first raw material, which includes homopolymer polypropylene, α-nucleating agent, antioxidant and processing aid, to obtain a first mixture. Step S2: The second raw material, including short glass fiber, rice husk carbon powder and silane coupling agent, is added to the first mixture and mixed to obtain the second mixture. Step S3: The second mixture is fed into an extruder, melt-extruded and granulated, and then dried to obtain a polypropylene composite material.

9. The preparation method according to claim 8, characterized in that, In step S3, the extruder includes a feeding section, a plasticizing section, a homogenizing section, and a die head section. The set temperature of the feeding section is 180~190℃, the set temperature of the plasticizing section is 200~220℃, the set temperature of the homogenizing section is 210~230℃, and the set temperature of the die head section is 220~240℃.

10. The preparation method according to claim 8, characterized in that, In step S1, the mixing temperature of the first raw material is 80~90℃, the mixing speed is 800~1000r / min, and the mixing time is 5~8min.

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