Bacteriostatic polypropylene-based wood-plastic composite material for vehicle and preparation method thereof

Abstract

The application provides a vehicle bacteriostatic polypropylene-based wood-plastic composite material and a preparation method. The vehicle bacteriostatic wood-plastic composite material comprises the following raw materials in parts by mass: 90 parts by mass of a polypropylene matrix, 20-40 parts by mass of modified plant fibers, 5-20 parts by mass of inorganic fillers, 1-3 parts by mass of a lubricant, and 0.1-2 parts by mass of an antioxidant. The modified plant fibers comprise plant fibers grafted with a grafting polymer and loaded with a pyridine antibacterial agent, and the grafting polymer comprises a polyunsaturated carboxylic acid segment and a polypropylene segment. The modified plant fibers have good compatibility with the polypropylene matrix and can be used to prepare wood-plastic composite materials, so that the mechanical properties, interface stability and long-term antibacterial properties of the composite materials are significantly improved.

Description

Technical Field

[0001] This application relates to the field of wood-plastic composite materials technology, specifically to an antibacterial polypropylene-based wood-plastic composite material for automobiles and its preparation method. Background Technology

[0002] With the development of new energy vehicles, polypropylene composites have been widely used due to their advantages such as lightweight, easy processing, and low price. However, interfacial compatibility issues have always existed when processing polypropylene with natural biomass materials such as plant fibers. This is due to the difference in raw materials; plant fibers are polar materials, resulting in poor interfacial bonding with non-polar plastics like polypropylene, which affects the mechanical properties, durability, and long-term stability of the composite material. To improve the compatibility between plant fibers and polypropylene, existing technologies typically use compatibilizers such as maleic anhydride-grafted polypropylene / POE to enhance the bonding force. While this method offers some improvement, it fails to fundamentally solve the interfacial defects caused by polarity differences and has limited effect on maintaining the long-term performance of the composite material.

[0003] In addition, the enclosed and humid environment inside a car is prone to the growth of microorganisms, which not only affects the interior environment but also accelerates the aging of materials. Currently, a common method is to directly add antibacterial agents, but antibacterial agents have poor compatibility with the polypropylene matrix and are prone to migrate to the material surface during processing and use, resulting in a decrease in the antibacterial performance of the material.

[0004] Therefore, there is a need to develop a wood-plastic composite material that can effectively improve the compatibility between plant fibers and polypropylene, and achieve long-term antibacterial stability. Summary of the Invention

[0005] This application provides an antibacterial polypropylene-based wood-plastic composite material for automobiles and its preparation method. The antibacterial polypropylene-based wood-plastic composite material for automobiles uses a polypropylene matrix as the main material and is optimized with modified plant fibers to improve the compatibility between antibacterial agents and plant fibers, thereby improving the overall performance of the antibacterial polypropylene-based wood-plastic composite material for automobiles.

[0006] In a first aspect, this application provides an antibacterial polypropylene-based wood-plastic composite material for automobiles, comprising the following raw materials in parts by weight: 90 parts by weight of polypropylene matrix, 20-40 parts by weight of modified plant fiber, 5-20 parts by weight of inorganic filler, 1-3 parts by weight of lubricant, and 0.1-2 parts by weight of antioxidant; wherein the modified plant fiber comprises plant fiber grafted with a graft polymer and loaded with a pyridine antibacterial agent, and the graft polymer comprises polyunsaturated carboxylic acid segments and polypropylene segments.

[0007] According to this application, the automotive antibacterial polypropylene-based wood-plastic composite material uses a polypropylene matrix as the main material. By adding plant fibers grafted with grafted polymers and loaded with pyridine antibacterial agents, the overall mechanical properties of the material can be improved, the antibacterial properties can be increased, and the long-lasting and highly effective antibacterial properties can be maintained.

[0008] Specifically, the polyunsaturated carboxylic acid segments in the grafted polymer contain -COOH, which can undergo esterification with -OH on plant fibers, increasing the surface polarity of the fibers and improving interfacial bonding. The polypropylene segments and the polypropylene matrix chains can physically entangle, with consistent molecular chain structures and good compatibility. The two can achieve tight bonding through intermolecular forces, avoiding interfacial separation. The two segments of the grafted polymer can act as "molecular bridges," improving the bonding strength between plant fibers and polypropylene materials.

[0009] On the other hand, loading pyridine antibacterial agents onto plant fibers can effectively enhance the antibacterial effect of the material. During melt processing, loading pyridine antibacterial agents onto the surface of plant fibers can reduce their migration during processing. Both pyridine antibacterial agents and plant fibers / polyunsaturated carboxylic acid segments are polar compounds. The compatibility between pyridine antibacterial agents and plant fibers grafted with grafted polymers is much greater than that between pyridine antibacterial agents and non-polar polypropylene matrices. During polymer melt processing, when pyridine antibacterial agents undergo molecular motion, they tend to remain on the surface of polar plant fibers rather than migrate into non-polar polypropylene. Simultaneously, the polypropylene segments in the grafted polymer will melt-entangle with the polypropylene matrix during processing, while the polycarboxylic acid segments will... Concentrated on the surface of plant fibers, the grafted polymer can form a physical barrier similar to a polymer brush, further fixing pyridine antibacterial agents to the plant fiber surface. During extrusion cooling, the hydroxyl groups on the surface of the plant fibers grafted with the polymer can reform hydrogen bonds with the pyridine antibacterial agents, thus achieving a highly efficient antibacterial structure in the composite material where the antibacterial agent is loaded onto the modified plant fibers, improving the material's high-efficiency antibacterial properties. Furthermore, the -COOH groups of the polycarboxylic acid segments near the plant fibers can coordinate with the pyridine antibacterial agents, further fixing them and preventing loss, aggregation, and inactivation, thereby improving the composite material's long-lasting antibacterial effect. Based on this, plant fibers grafted with the polymer can improve the processing stability and long-term use stability of pyridine antibacterial agents in a polypropylene matrix, increasing the long-term antibacterial stability of the system.

[0010] In some embodiments, the modified plant fiber is further loaded with a high molecular weight hindered amine light stabilizer containing NH bonds, wherein the weight-average molecular weight of the hindered amine light stabilizer is 3000~15000 Da.

[0011] In some of the above embodiments, the inventors discovered that when using antibacterial functionalized plant fibers grafted with grafted polymers to load high-molecular-weight hindered amine light stabilizers containing NH bonds, not only is the anti-aging performance of the material improved, but the long-term antibacterial properties of the material are also unexpectedly optimized. This may be because the hindered amine light stabilizer molecules contain NH bonds, which can be dually fixed to the plant fibers based on the adsorption effect of the modified plant fibers and the hydrogen bonding effect of the active groups of the modified plant fibers. In addition, the polyunsaturated carboxylic acid segments grafted onto the surface of the modified plant fibers form a regional hydrogen bond fixation network, while the molecules... The inner piperidine ring structure provides basic sites, which can further promote its binding with pyridine antibacterial agents, thereby further immobilizing the antibacterial agents. Due to its high molecular weight, the molecular chain can physically entangle on the rough surface of plant fibers or entangle with polyunsaturated carboxylic acid segments. During melt processing, the high molecular weight NH-bonded hindered amine light stabilizer is fixed to the surface of plant fibers on the one hand through the physical barrier effect of polyunsaturated carboxylic acid segments, and on the other hand, it may reduce the migration of light stabilizers to the polypropylene matrix through the entanglement effect brought about by the high molecular weight, thus effectively fixing the light stabilizer to the surface of plant fibers. After extrusion and cooling, the long-chain structure can form a partial cover on the fiber surface, providing multiple binding sites for antibacterial agents on the one hand, and slowing down the migration of antibacterial agents to the polypropylene matrix or material surface through its steric hindrance effect on the other hand. Therefore, adding high molecular weight NH-bonded hindered amine light stabilizers to the system can not only protect pyridine antibacterial agents and material stability during long-term use through their traditional UV protection capabilities, but also further improve the stability of antibacterial agents in composite materials.

[0012] In some embodiments, the inorganic filler comprises silane-modified calcium carbonate and nano-silica, wherein the silane-modified calcium carbonate comprises calcium carbonate surface-treated with a silane coupling agent containing alkoxy groups and unsaturated organic groups, and the mass ratio of the silane-modified calcium carbonate to nano-silica is (4~10):1.

[0013] In some embodiments, the average particle size of the calcium carbonate is 1-5 μm, and the average particle size of the nano-silica is 10-50 nm.

[0014] In some of the above embodiments, calcium carbonate and nano-silica, surface-treated with silane coupling agents containing alkoxy and unsaturated organic groups, are compounded in the above proportions as inorganic fillers. Micron-sized silane-modified calcium carbonate can serve as a rigid filler to enhance the mechanical properties of the material. Simultaneously, its surface contains organic groups, exhibiting good compatibility with the polypropylene matrix. It can also bond with the hydroxyl groups on the plant fiber surface through hydrogen bonds, thereby forming a fiber-filler-matrix bond, further improving interfacial bonding and enhancing the overall material performance. Nano-silica, combined with micron-sized calcium carbonate, provides mechanical reinforcement. Furthermore, its surface hydroxyl groups can form a hydrogen bond network with hydroxyl, carboxyl, or hindered amine light stabilizers, providing anchoring and dispersing effects on polyunsaturated carboxylic acid segments, light stabilizers, and antibacterial agents, thereby further stabilizing the antibacterial agents and light stabilizers on the plant fiber surface. Therefore, the above-mentioned compounded inorganic filler can simultaneously improve the mechanical properties, antibacterial properties, and UV resistance of the composite material.

[0015] In some embodiments, the silane-modified calcium carbonate is prepared by including the following steps:

[0016] M1: Mix 100 parts by mass of calcium carbonate and 1-3 parts by mass of γ-methacryloyloxypropyltrimethoxysilane, then add 300-700 parts by mass of an aqueous ethanol solution (ethanol-water volume ratio 1:1), stir at 60-90℃ for 1-3 hours, filter and dry to obtain silane-modified calcium carbonate.

[0017] In some embodiments, the modified plant fiber is prepared by including the following steps:

[0018] S1: Grafting polypropylene and decahydronaphthalene are dispersed in anhydrous ethanol, and the grafting polypropylene is swollen under the action of decahydronaphthalene to obtain grafting polypropylene treated with decahydronaphthalene.

[0019] S2: Graft copolymer is obtained by dispersing decahydronaphthalene-treated grafted polypropylene, unsaturated carboxylic acid monomers, and initiators in water.

[0020] S3: Mix the grafted polymer with plant fiber, so that the carboxyl groups on the grafted polymer condense with the hydroxyl groups on the plant fiber to obtain plant fiber grafted with the grafted polymer.

[0021] S4: Mix the pyridine antibacterial agent with the plant fiber grafted with the grafted polymer, so that the pyridine antibacterial agent is loaded on the plant fiber grafted with the grafted polymer, and antibacterial functionalized plant fiber grafted with the grafted polymer is obtained as modified plant fiber.

[0022] In some of the above embodiments, a method for preparing modified plant fibers is described. Specifically, an initiator is used to initiate the generation of polypropylene free radicals for grafting. These radicals react with the double bonds of unsaturated carboxylic acid monomers to form a polypropylene-g-polyunsaturated carboxylic acid graft polymer. The graft polymer is then reacted with plant fibers, where it undergoes partial esterification with the plant fibers through the polyunsaturated carboxylic acid segments. Finally, pyridine-based antibacterial agents are loaded using the polyunsaturated carboxylic acid segments and the plant fibers to obtain modified plant fibers. The modified plant fibers prepared by the above method have good compatibility with polypropylene materials, thereby improving the mechanical properties, interfacial stability, and long-term antibacterial stability of wood-plastic composites.

[0023] In some embodiments, the method for preparing the modified plant fiber further includes the following steps:

[0024] S5: The antibacterial functionalized plant fiber grafted with the grafted polymer is mixed with a high molecular weight hindered amine light stabilizer containing NH bonds, so that the high molecular weight hindered amine light stabilizer containing NH bonds is loaded onto the modified plant fiber, and an antibacterial and anti-ultraviolet multifunctional plant fiber grafted with the grafted polymer is obtained as the modified plant fiber.

[0025] In some of the above embodiments, introducing a high molecular weight NH bond-containing hindered amine light stabilizer onto the surface of plant fibers can not only give the plant fibers a multifunctional antibacterial and anti-UV effect, but also improve the long-lasting antibacterial performance of the antibacterial agent in wood-plastic composites through the fixation of the plant fiber surface interface and the steric hindrance effect.

[0026] In some embodiments, the plant fiber includes at least one of bamboo fiber, coconut shell fiber, rice husk fiber, and hemp fiber.

[0027] In some of the above embodiments, the selected plant fibers have a high aspect ratio and high strength, which can act as a reinforcing phase in wood-plastic composites. Their surfaces are rich in hydroxyl functional groups, which can provide reaction sites for grafted polymers. At the same time, the plant fibers all have a high specific surface area, which can provide more adsorption sites for antibacterial agents and enhance the antibacterial effect.

[0028] In some embodiments, the pyridine antibacterial agent includes at least one of zinc pyridinethione and copper pyridinethione.

[0029] In some of the above embodiments, pyridine-based antibacterial agents, such as zinc pyridinethione and / or copper pyridinethione, can coordinate with the polycarboxylic acid segments of the grafted polymer, alleviating the migration problem of the antibacterial agent during processing or use, and providing good long-lasting antibacterial properties for the composite material.

[0030] In some embodiments, the polyunsaturated carboxylic acid segment includes at least one of polyacrylic acid segment and polymethacrylic acid segment.

[0031] In some of the above embodiments, the polyunsaturated carboxylic acid segments are made of polyacrylic acid segments and / or polymethacrylic acid segments, which can bind well with plant fibers while improving the stability of the antibacterial agent on the surface of plant fibers.

[0032] In some embodiments, the weight-average molecular weight of the grafted polypropylene is 10,000 to 50,000 Da. In the above embodiments, grafted polypropylene with the above-mentioned weight-average molecular weight is used, where the grafted polypropylene serves as a functional chain segment, and the overall strength of the material is provided by the polypropylene matrix. As an example, in one embodiment of this application, the weight-average molecular weight of the grafted polypropylene is 20,000 Da.

[0033] In some embodiments, the method for preparing the modified plant fiber includes the following steps:

[0034] S1: 20 parts by weight of grafting polypropylene, 10-60 parts by weight of decahydronaphthalene and 200-400 parts by weight of anhydrous ethanol are mixed and heated to 70-80°C. After treatment under an inert atmosphere for 30-90 minutes, grafting polypropylene treated with decahydronaphthalene is obtained.

[0035] S2: 10 parts by mass of grafted polypropylene treated with decahydronaphthalene, 0.1-0.5 parts by mass of BPO, and 2-4 parts by mass of acrylic acid are dispersed in 20-40 parts by mass of water. After reacting at 60-90°C for 3-4 hours under an inert atmosphere, PP-g-PAA grafted polymer is obtained.

[0036] S3: Disperse 10 parts by mass of PP-g-PAA grafted polymer, 15-30 parts by mass of plant fiber, 1-3 parts by mass of acetic acid, and 0.1-1 parts by mass of 4A molecular sieve in 50-120 parts by mass of dimethyl sulfoxide, and react at 60-90℃ for 1-3 hours to obtain plant fiber grafted with grafted polymer.

[0037] S4: Disperse 15 parts by mass of plant fiber grafted with grafted polymer and 1-5 parts by mass of zinc pyrithione in 20-60 parts by mass of anhydrous ethanol, and treat at 30-60℃ for 2-3 hours to obtain antibacterial functionalized plant fiber grafted with grafted polymer.

[0038] S5: Disperse 15 parts by mass of antibacterial functionalized plant fiber grafted with graft polymer and 1-5 parts by mass of high molecular weight hindered amine light stabilizer containing NH bond in 50-150 parts by mass of anhydrous ethanol, and treat at 30-60℃ for 3-6 hours to obtain antibacterial and UV-resistant multifunctional plant fiber grafted with graft polymer, as modified plant fiber.

[0039] The above methods specifically illustrate the reaction conditions and dosage ratios of each step in the preparation of modified plant fibers. Under these conditions, modified plant fibers with polypropylene segments on the surface and loaded with antibacterial agents can be obtained, which can make the antibacterial agents have better stability in composite materials.

[0040] In some embodiments, the weight-average molecular weight of the polypropylene matrix is ​​100,000 to 300,000 Da. In the above embodiments, using a polypropylene matrix with the aforementioned weight-average molecular weight indicates that its molecular chains are longer and its entanglement is higher. A high molecular weight polypropylene matrix exhibits superior mechanical properties and thermal stability. Wood-plastic composites produced from polypropylene matrices within this molecular weight range can meet the requirements for mechanical properties and thermal stability in automotive environments. As an example, in one embodiment of this application, the weight-average molecular weight of the polypropylene matrix used is 250,000 Da.

[0041] In some embodiments, the lubricant includes at least one selected from zinc stearate, magnesium stearate, and calcium stearate. As an example, zinc stearate is used as the lubricant in one embodiment of this application.

[0042] In some embodiments, the antioxidant includes at least one of antioxidant 1010, antioxidant 1076, and antioxidant 168. As an example, antioxidant 1010 is used as the antioxidant in one embodiment of this application.

[0043] Secondly, this application provides a method for preparing an antibacterial polypropylene-based wood-plastic composite material for automobiles, comprising:

[0044] Provide raw materials for automotive antibacterial polypropylene-based wood-plastic composite materials according to any embodiment of the first aspect;

[0045] The raw materials are mixed and then melt-extruded to obtain an antibacterial polypropylene-based wood-plastic composite material for automotive applications.

[0046] According to this application, the method can prepare the first aspect of the antibacterial polypropylene-based wood-plastic composite material for automobiles, thus having the first aspect of the beneficial effects. Through the above method, an antibacterial polypropylene-based wood-plastic composite material for automobiles with good compatibility between plant fiber and polypropylene and long-lasting antibacterial properties can be obtained.

[0047] Thirdly, this application also provides a plastic component for automobiles, including an antibacterial polypropylene-based wood-plastic composite material for automobiles as described in any embodiment of the first aspect or an antibacterial polypropylene-based wood-plastic composite material for automobiles prepared by the method described in any embodiment of the second aspect.

[0048] According to this application, the wood-plastic composite material is used in automotive plastic parts, which can not only improve the mechanical properties of the material to meet the long-term use requirements of the automotive interior environment, but also improve the long-term antibacterial and UV resistance properties of the material.

[0049] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0050] By grafting polypropylene-g-polyunsaturated carboxylic acid polymer onto the surface of plant fibers, the interfacial bonding strength between the plant fibers and the polypropylene matrix is ​​improved, thus enhancing the mechanical properties of the wood-plastic composite. Furthermore, by loading pyridine antibacterial agents onto the plant fiber surface, synergistically fixing the antibacterial agents with carboxyl groups on the polyunsaturated carboxylic acid segments, the long-term stability of the antibacterial agents within the material is achieved. Additionally, the introduction of high-molecular-weight hindered amine light stabilizers containing NH bonds achieves a multi-functional synergistic effect of antibacterial and UV protection through steric hindrance and hydrogen bonding. Simultaneously, the composite filling of silane-modified calcium carbonate and nano-silica enhances the material's mechanical properties while synergistically optimizing antibacterial and UV protection properties in conjunction with the modified plant fibers. Therefore, the automotive antibacterial polypropylene-based wood-plastic composite provided in this application possesses excellent mechanical properties, long-lasting antibacterial activity, and weather resistance, meeting the long-term needs of automotive interiors in complex environments. Detailed Implementation

[0051] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0053] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0054] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0055] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0057] Polypropylene matrix, grade: 1215C, weight average molecular weight is 250,000 Da;

[0058] The grafted polypropylene has a weight-average molecular weight of 20,000 Da.

[0059] Polyacrylic acid, weight average molecular weight 3000 Da;

[0060] 4A molecular sieve, 3mm in diameter, 4A pore size, CAS No.: 70955-01-0;

[0061] Plant fiber, brand: BF-2120, 120 mesh;

[0062] The hindered amine light stabilizer is light stabilizer 2020, with a weight-average molecular weight of 3300 Da and CAS number: 192268-64-7.

[0063] Light stabilizer 770, weight-average molecular weight 770 Da, CAS number: 52829-07-9;

[0064] PP-g-MAH, grade B1, grafting rate 1.2%;

[0065] Calcium carbonate, with an average particle size of 2 μm;

[0066] Silica, with an average particle size of 20 nm;

[0067] Antioxidant, Antioxidant 1010, CAS No.: 6683-19-8;

[0068] Lubricant, zinc stearate, CAS No.: 557-05-1.

[0069] Preparation Example 1

[0070] Preparation of modified plant fibers:

[0071] 20 parts by weight of grafting polypropylene, 30 parts by weight of decahydronaphthalene and 300 parts by weight of anhydrous ethanol were mixed and heated to 75°C. After stirring for 60 minutes under nitrogen protection, the mixture was naturally cooled to 45°C, washed three times by centrifugation with anhydrous ethanol, and dried to obtain polypropylene treated with decahydronaphthalene.

[0072] 10 parts by mass of grafted polypropylene treated with decahydronaphthalene, 0.2 parts by mass of BPO, and 3 parts by mass of acrylic acid were dispersed in 30 parts by mass of water. Nitrogen gas was introduced, the temperature was raised to 70°C, and the mixture was stirred at 800 rpm for 3 hours. After stirring, the mixture was cooled to 20°C, filtered, and the solid was washed three times with water and then twice with anhydrous ethanol. The solid was then dried under vacuum to obtain the PP-g-PAA grafted polymer.

[0073] Dissolve 10 parts by mass of PP-g-PAA grafted polymer in 100 parts by mass of dimethyl sulfoxide, then add 25 parts by mass of bamboo fiber, 2 parts by mass of acetic acid, and 0.5 parts by mass of 4A molecular sieve. Heat to 80°C and stir for 2 hours. Remove the solid component, wash twice with anhydrous ethanol, and dry to obtain bamboo fiber grafted with grafted polymer.

[0074] 15 parts by mass of bamboo fiber grafted with grafted polymer and 2.5 parts by mass of zinc pyridinethione were dispersed in 40 parts by mass of anhydrous ethanol. The mixture was stirred at 45°C for 2 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial functionalized bamboo fiber grafted with grafted polymer.

[0075] 15 parts by weight of antibacterial functionalized bamboo fiber grafted with grafted polymer and 2.5 parts by weight of light stabilizer 2020 were dispersed in 100 parts by weight of anhydrous ethanol. The mixture was stirred at 45°C for 5 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial and UV-resistant multifunctional bamboo fiber grafted with grafted polymer, which was used as a modified plant fiber.

[0076] Preparation Example 2

[0077] Preparation of modified plant fibers:

[0078] 20 parts by weight of grafting polypropylene, 30 parts by weight of decahydronaphthalene and 300 parts by weight of anhydrous ethanol were mixed and heated to 75°C. After stirring for 60 minutes under nitrogen protection, the mixture was naturally cooled to 45°C, washed three times by centrifugation with anhydrous ethanol, and dried to obtain polypropylene treated with decahydronaphthalene.

[0079] Ten parts by mass of grafted polypropylene treated with decahydronaphthalene, 0.2 parts by mass of BPO, and 3 parts by mass of acrylic acid were dispersed in 30 parts by mass of water. Nitrogen gas was introduced, and the mixture was heated to 70°C and stirred at 800 rpm for 3 hours. After stirring, the mixture was cooled to 20°C, filtered, and the solid was washed three times with water and then twice with anhydrous ethanol. The solid was then dried under vacuum to obtain the PP-g-PAA grafted polymer.

[0080] Dissolve 10 parts by mass of PP-g-PAA grafted polymer in 100 parts by mass of dimethyl sulfoxide, then add 25 parts by mass of bamboo fiber, 2 parts by mass of acetic acid, and 0.5 parts by mass of 4A molecular sieve. Heat to 80°C and stir for 2 hours. Remove the solid component, wash twice with anhydrous ethanol, and dry to obtain bamboo fiber grafted with grafted polymer.

[0081] 15 parts by mass of bamboo fiber grafted with grafted polymer and 2.5 parts by mass of zinc pyrithione were dispersed in 40 parts by mass of anhydrous ethanol. The mixture was stirred at 45°C for 2 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial functionalized bamboo fiber grafted with grafted polymer, which was used as modified plant fiber.

[0082] Preparation Example 3

[0083] Preparation of modified plant fibers:

[0084] 20 parts by weight of grafting polypropylene, 30 parts by weight of decahydronaphthalene and 300 parts by weight of anhydrous ethanol were mixed and heated to 75°C. After stirring for 60 minutes under nitrogen protection, the mixture was naturally cooled to 45°C, washed three times by centrifugation with anhydrous ethanol, and dried to obtain polypropylene treated with decahydronaphthalene.

[0085] Ten parts by mass of grafted polypropylene treated with decahydronaphthalene, 0.2 parts by mass of BPO, and 3 parts by mass of acrylic acid were dispersed in 30 parts by mass of water. Nitrogen gas was introduced, and the mixture was heated to 70°C and stirred at 800 rpm for 3 hours. After stirring, the mixture was cooled to 20°C, filtered, and the solid was washed three times with water and then twice with anhydrous ethanol. The solid was then dried under vacuum to obtain the PP-g-PAA grafted polymer.

[0086] Dissolve 10 parts by mass of PP-g-PAA grafted polymer in 100 parts by mass of dimethyl sulfoxide, then add 25 parts by mass of bamboo fiber, 2 parts by mass of acetic acid, and 0.5 parts by mass of 4A molecular sieve. Heat to 80°C and stir for 2 hours. Remove the solid component, wash twice with anhydrous ethanol, and dry to obtain bamboo fiber grafted with grafted polymer.

[0087] 15 parts by mass of bamboo fiber grafted with grafted polymer and 2.5 parts by mass of zinc pyridinethione were dispersed in 40 parts by mass of anhydrous ethanol. The mixture was stirred at 45°C for 2 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial functionalized bamboo fiber grafted with grafted polymer.

[0088] 15 parts by weight of antibacterial functionalized bamboo fiber grafted with grafted polymer and 2.5 parts by weight of light stabilizer 770 were dispersed in 100 parts by weight of anhydrous ethanol. The mixture was stirred at 45°C for 5 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial and UV-resistant multifunctional bamboo fiber grafted with grafted polymer, which was used as a modified plant fiber.

[0089] Preparation Example 4

[0090] Preparation of modified plant fibers:

[0091] 20 parts by weight of grafting polypropylene, 30 parts by weight of decahydronaphthalene and 300 parts by weight of anhydrous ethanol were mixed and heated to 75°C. After stirring for 60 minutes under nitrogen protection, the mixture was naturally cooled to 45°C, washed three times by centrifugation with anhydrous ethanol, and dried to obtain polypropylene treated with decahydronaphthalene.

[0092] Ten parts by mass of grafted polypropylene treated with decahydronaphthalene, 0.2 parts by mass of BPO, and 3 parts by mass of acrylic acid were dispersed in 30 parts by mass of water. Nitrogen gas was introduced, and the mixture was heated to 70°C and stirred at 800 rpm for 3 hours. After stirring, the mixture was cooled to 20°C, filtered, and the solid was washed three times with water and then twice with anhydrous ethanol. The solid was then dried under vacuum to obtain the PP-g-PAA grafted polymer.

[0093] Dissolve 10 parts by mass of PP-g-PAA grafted polymer in 100 parts by mass of dimethyl sulfoxide, then add 25 parts by mass of bamboo fiber, 2 parts by mass of acetic acid, and 0.5 parts by mass of 4A molecular sieve. Heat to 80°C and stir for 2 hours. Remove the solid component, wash twice with anhydrous ethanol, and dry to obtain bamboo fiber grafted with grafted polymer.

[0094] 15 parts by mass of bamboo fiber grafted with grafted polymer and 2.5 parts by mass of bispyridinethione were dispersed in 40 parts by mass of anhydrous ethanol. The mixture was stirred at 45°C for 2 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial functionalized bamboo fiber grafted with grafted polymer.

[0095] 15 parts by weight of antibacterial functionalized bamboo fiber grafted with grafted polymer and 2.5 parts by weight of light stabilizer 2020 were dispersed in 100 parts by weight of anhydrous ethanol. The mixture was stirred at 45°C for 5 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial and UV-resistant multifunctional bamboo fiber grafted with grafted polymer, which was used as a modified plant fiber.

[0096] Comparative Preparation Example 1

[0097] Preparation of modified plant fibers:

[0098] 20 parts by weight of grafting polypropylene, 30 parts by weight of decahydronaphthalene and 300 parts by weight of anhydrous ethanol were mixed and heated to 75°C. After stirring for 60 minutes under nitrogen protection, the mixture was naturally cooled to 45°C, washed three times by centrifugation with anhydrous ethanol, and dried to obtain polypropylene treated with decahydronaphthalene.

[0099] Ten parts by mass of grafted polypropylene treated with decahydronaphthalene, 0.2 parts by mass of BPO, and 3 parts by mass of acrylic acid were dispersed in 30 parts by mass of water. Nitrogen gas was introduced, and the mixture was heated to 70°C and stirred at 800 rpm for 3 hours. After stirring, the mixture was cooled to 20°C, filtered, and the solid was washed three times with water and then twice with anhydrous ethanol. The solid was then dried under vacuum to obtain the PP-g-PAA grafted polymer.

[0100] Dissolve 10 parts by mass of PP-g-PAA grafted polymer in 100 parts by mass of dimethyl sulfoxide, then add 25 parts by mass of bamboo fiber, 2 parts by mass of acetic acid, and 0.5 parts by mass of 4A molecular sieve. Heat to 80°C and stir for 2 hours. Remove the solid component, wash twice with anhydrous ethanol, and dry to obtain bamboo fiber grafted with grafted polymer.

[0101] 15 parts by weight of bamboo fiber grafted with polymer and 2.5 parts by weight of light stabilizer 2020 were dispersed in 100 parts by weight of anhydrous ethanol. The mixture was stirred at 45°C for 5 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain UV-resistant functionalized bamboo fiber grafted with polymer, which was used as a modified plant fiber.

[0102] Comparative Preparation Example 2

[0103] Preparation of modified plant fibers:

[0104] Dissolve 10 parts by mass of PAA polymer in 100 parts by mass of dimethyl sulfoxide, then add 25 parts by mass of bamboo fiber, 2 parts by mass of acetic acid, and 0.5 parts by mass of 4A molecular sieve. Heat to 80°C and stir for 2 hours. Remove the solid component, wash twice with anhydrous ethanol, and dry to obtain bamboo fiber grafted with polymer.

[0105] 15 parts by mass of polymer-grafted bamboo fiber and 2.5 parts by mass of zinc pyrithione were dispersed in 40 parts by mass of anhydrous ethanol. The mixture was stirred at 45°C for 2 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial functionalized polymer-grafted bamboo fiber.

[0106] 15 parts by weight of antibacterial bamboo fiber and 2.5 parts by weight of light stabilizer 2020 were dispersed in 100 parts by weight of anhydrous ethanol. The mixture was stirred at 45°C for 5 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial and UV-resistant multifunctional bamboo fiber grafted with polymer, which was used as a modified plant fiber.

[0107] Comparative preparation example 3

[0108] Preparation of modified plant fibers:

[0109] Dissolve 10 parts by mass of PP-g-MAH in 100 parts by mass of dimethyl sulfoxide, then add 25 parts by mass of bamboo fiber, 2 parts by mass of acetic acid, and 0.5 parts by mass of 4A molecular sieve. Heat to 80°C and stir for 2 hours. Remove the solid component, wash twice with anhydrous ethanol, and dry to obtain bamboo fiber grafted with the grafted polymer.

[0110] 15 parts by mass of bamboo fiber grafted with grafted polymer and 2.5 parts by mass of zinc pyridinethione were dispersed in 40 parts by mass of anhydrous ethanol. The mixture was stirred at 45°C for 2 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial functionalized bamboo fiber grafted with grafted polymer.

[0111] 15 parts by weight of antibacterial functionalized bamboo fiber grafted with grafted polymer and 2.5 parts by weight of light stabilizer 2020 were dispersed in 100 parts by weight of anhydrous ethanol. The mixture was stirred at 45°C for 5 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and dried to obtain antibacterial and UV-resistant multifunctional bamboo fiber grafted with grafted polymer, which was used as a modified plant fiber.

[0112] Example 1

[0113] Preparation of antibacterial polypropylene-based wood-plastic composite materials for automotive applications:

[0114] 100 parts by mass of calcium carbonate and 2 parts by mass of γ-methacryloyloxypropyltrimethoxysilane were mixed and then added to 500 parts by mass of an aqueous ethanol solution (ethanol-water volume ratio 1:1). The mixture was stirred at 300 rpm for 2 hours at 80°C, filtered, and dried to obtain silane-modified calcium carbonate.

[0115] 90 parts by mass of polypropylene matrix, 30 parts by mass of modified plant fiber obtained in Preparation Example 1, 8 parts by mass of silane-modified calcium carbonate, 2 parts by mass of nano-silica, 1 part by mass of antioxidant 1010, and 2 parts by mass of zinc stearate were mixed and melt-extruded and granulated at 180°C to obtain an antibacterial polypropylene-based wood-plastic composite material for automotive use.

[0116] Example 2

[0117] Preparation of antibacterial polypropylene-based wood-plastic composite materials for automotive applications:

[0118] 100 parts by mass of calcium carbonate and 2 parts by mass of γ-methacryloyloxypropyltrimethoxysilane were mixed and then added to 500 parts by mass of an aqueous ethanol solution (ethanol-water volume ratio 1:1). The mixture was stirred at 300 rpm for 2 hours at 80°C, filtered, and dried to obtain silane-modified calcium carbonate.

[0119] 90 parts by mass of polypropylene matrix, 25.71 parts by mass of modified plant fiber obtained in Preparation Example 2, 8 parts by mass of silane-modified calcium carbonate, 2 parts by mass of nano-silica, 1 part by mass of antioxidant 1010, 2 parts by mass of zinc stearate, and 4.29 parts by mass of light stabilizer 2020 were mixed and melt-extruded and granulated at 180°C to obtain an antibacterial polypropylene-based wood-plastic composite material for automotive use.

[0120] Example 3

[0121] Preparation of antibacterial polypropylene-based wood-plastic composite materials for automotive applications:

[0122] It is largely the same as Example 1, except that the modified plant fiber obtained in Preparation Example 3 is used.

[0123] Example 4

[0124] Preparation of antibacterial polypropylene-based wood-plastic composite materials for automotive applications:

[0125] It is largely the same as Example 1, except that the modified plant fiber obtained in Preparation Example 4 is used.

[0126] Example 5

[0127] Preparation of antibacterial polypropylene-based wood-plastic composite materials for automotive applications:

[0128] 90 parts by mass of polypropylene matrix, 30 parts by mass of modified plant fiber obtained in Preparation Example 1, 8 parts by mass of calcium carbonate, 2 parts by mass of nano-silica, 1 part by mass of antioxidant 1010, and 2 parts by mass of zinc stearate were mixed and melt-extruded and granulated at 180°C to obtain an antibacterial polypropylene-based wood-plastic composite material for automotive use.

[0129] Comparative Example 1

[0130] Preparation of antibacterial polypropylene-based wood-plastic composite materials for automotive applications:

[0131] 100 parts by mass of calcium carbonate and 2 parts by mass of γ-methacryloyloxypropyltrimethoxysilane were mixed and then added to 500 parts by mass of an aqueous ethanol solution (ethanol-water volume ratio 1:1). The mixture was stirred at 300 rpm for 2 hours at 80°C, filtered, and dried to obtain silane-modified calcium carbonate.

[0132] 90 parts by mass of polypropylene matrix, 26.33 parts by mass of modified plant fiber obtained in Comparative Preparation Example 1, 3.67 parts by mass of zinc pyridinethione, 8 parts by mass of silane-modified calcium carbonate, 2 parts by mass of nano-silica, 1 part by mass of antioxidant 1010, and 2 parts by mass of zinc stearate were mixed and melt-extruded and granulated at 180°C to obtain an antibacterial polypropylene-based wood-plastic composite material for automotive use.

[0133] Comparative Example 2

[0134] Preparation of antibacterial polypropylene-based wood-plastic composite materials for automotive applications:

[0135] It is largely the same as Example 1, except that the modified plant fiber obtained in Comparative Preparation Example 2 was used.

[0136] Comparative Example 3

[0137] Preparation of antibacterial polypropylene-based wood-plastic composite materials for automotive applications:

[0138] It is largely the same as Example 1, except that the modified plant fiber obtained in Comparative Preparation Example 3 was used.

[0139] Test section:

[0140] Antibacterial activity test: The products obtained from the above preparation examples and comparative examples were pressed into plates with a size of 50 mm using a plate vulcanizer at 200°C and 1 MPa pressure. The prepared sample, 50mm in diameter and 8mm thick, was subjected to an antibacterial test according to GB / T 31402-2023, "Determination of antibacterial activity of surfaces of plastics and other non-porous materials". The tested bacteria was Escherichia coli ATCC 8739.

[0141] Long-lasting antibacterial activity test: The products obtained from the above preparation examples and comparative examples were pressed into plates with a size of 50 mm using a plate vulcanizer at 200°C and 1 MPa pressure. The prepared samples, 50mm in diameter and 8mm thick, were placed in a UV aging chamber for 1000 hours. The treatment conditions were: UV-A 340nm, light intensity: 0.7W / m², black panel temperature: 60℃, and relative humidity: (50±5)%RH. After treatment, antibacterial performance was tested according to GB / T 31402-2023, "Determination of antibacterial activity of plastics and other non-porous materials". The tested bacteria was Escherichia coli ATCC 8739.

[0142] Tensile strength test: The products obtained from the above preparation examples and comparative examples were pressed into sheets at 200℃ and 1MPa pressure using a flat vulcanizing apparatus. Type II specimens were prepared according to GB 1040-79 "Plastics Tensile Testing Method". The specimens were stretched at 100mm / min on a universal testing machine, and the tensile yield strength was recorded.

[0143] Table 1

[0144]

[0145] According to Table 1, the wood-plastic composite materials obtained in each embodiment have higher long-term antibacterial rates and tensile yield strengths compared to the comparative examples, indicating that the automotive antibacterial polypropylene-based wood-plastic composite material provided by this patent has good long-term antibacterial properties and mechanical strength. The reason for this may be that in Comparative Example 1, zinc pyrithione was directly added to the polypropylene matrix. Since zinc pyrithione is a polar molecule, it has poor compatibility with the polypropylene matrix. During processing and use, it migrates or precipitates to the surface, resulting in loss of the antibacterial agent after long-term use, leading to a significant decrease in the long-term antibacterial rate. Simultaneously, the blended antibacterial agent powder is difficult to disperse evenly, forming agglomerates within the matrix, resulting in a slight decrease in tensile yield strength. In Comparative Example 2, only polyacrylic acid was grafted onto modified plant fibers. Although the carboxyl groups in polyacrylic acid can bind well with plant fibers, they themselves do not readily combine with polyacrylic acid. The incompatibility of the alkenyl matrix may form an incompatible interface between the plant fiber and polypropylene, leading to a decrease in mechanical properties. Although the carboxyl groups in polyacrylic acid can fix the antibacterial agent, due to defects in the overall interface, the antibacterial agent will fall off as the interface breaks down during aging, resulting in a decrease in antibacterial performance. In Comparative Example 3, PP-g-MAH modified plant fiber is used. Although it has a certain degree of compatibility, the maleic anhydride group cannot form a coordination structure with the pyridine antibacterial agent. During long-term use and aging, the antibacterial agent is prone to desorb from the fiber surface and migrate to the surface, resulting in a decrease in long-term antibacterial performance.

[0146] As shown in Examples 1, 2, and 3, the type and loading method of hindered amine light stabilizers have a certain impact on the long-term antibacterial and mechanical properties of wood-plastic composites. In Example 2, light stabilizer 2020 was not loaded onto the plant fibers. The light stabilizer was added during blending, and most of it was dispersed in the polypropylene matrix. A small portion may migrate to the plant fiber interface to exert its effect, resulting in a decrease in the fixation and anti-migration ability of the antibacterial agent. During processing, the antibacterial agent may migrate, leading to a decrease in antibacterial and long-term antibacterial properties. In Example 3, the plant fibers were loaded with a low molecular weight NH-containing hindered amine light stabilizer. Its short molecular weight cannot form a molecular barrier to prevent the migration of antibacterial agent molecules, resulting in a decrease in long-term antibacterial properties. Therefore, using plant fibers loaded with a high molecular weight NH-containing hindered amine light stabilizer can give wood-plastic composites good long-term antibacterial and mechanical properties.

[0147] As shown in Examples 1 and 4, the type of antibacterial agent has a certain impact on the long-term antibacterial performance of wood-plastic composites. In Example 4, the antibacterial agent bispyridinethione was used, and its initial antibacterial effect was lower than that of zinc pyridinethione. Due to the lack of metal ions in the molecule, it cannot form coordination with the carboxyl groups in PP-g-PAA, resulting in a weaker bond between the antibacterial agent and the modified plant fiber. Furthermore, bispyridinethione has lower thermal stability than zinc pyridinethione, making it prone to decomposition and migration during melt extrusion. Therefore, both the antibacterial performance and the long-term antibacterial performance decreased. Thus, when a pyridine-based antibacterial agent containing metal ions is selected, the antibacterial performance of the wood-plastic composite is the best.

[0148] As shown in Examples 1 and 5, the surface treatment of the filler has a certain impact on the long-term antibacterial properties and mechanical properties of wood-plastic composites. In Example 5, the calcium carbonate was not modified with silane, resulting in weak interfacial bonding with polypropylene, a slight decrease in strength, and a tendency for microcracks to form during aging, leading to easy migration of the antibacterial agent. Therefore, when using silane-modified calcium carbonate, the wood-plastic composite exhibits the best long-term antibacterial properties and mechanical properties.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A bacteriostatic polypropylene-based wood plastic composite for vehicle, characterized in that, The raw materials include 90 parts by mass of polypropylene matrix, 20-40 parts by mass of modified plant fiber, 5-20 parts by mass of inorganic filler, 1-3 parts by mass of lubricant, and 0.1-2 parts by mass of antioxidant. The modified plant fiber comprises plant fiber grafted with graft polymer and loaded with pyridine antibacterial agent, the graft polymer comprises polyunsaturated carboxylic acid segment and polypropylene segment, and the pyridine antibacterial agent comprises at least one of zinc pyrithione and copper pyrithione. The preparation method of the modified plant fiber comprises the following steps: S1: dispersing grafting polypropylene and decalin in anhydrous ethanol, swelling the grafting polypropylene under the action of decalin to obtain decalin-treated grafting polypropylene; S2: dispersing the decalin-treated grafting polypropylene, unsaturated carboxylic acid monomer and initiator in water to graft copolymerize to obtain graft polymer; S3: mixing the graft polymer and plant fiber to condense carboxyl on the graft polymer with hydroxyl on the plant fiber to obtain plant fiber grafted with graft polymer; S4: mixing pyridine antibacterial agent with the plant fiber grafted with graft polymer to load the pyridine antibacterial agent on the plant fiber grafted with graft polymer to obtain antibacterial functional plant fiber grafted with graft polymer; S5: mixing the antibacterial functional plant fiber grafted with graft polymer with high molecular weight N-H bond-containing hindered amine light stabilizer to load the high molecular weight N-H bond-containing hindered amine light stabilizer on the modified plant fiber to obtain antibacterial and ultraviolet-resistant multifunctional plant fiber grafted with graft polymer as the modified plant fiber; wherein the weight average molecular weight of the hindered amine light stabilizer is 2000-10000 Da.

2. The wood-plastic composite material according to claim 1, wherein the wood-plastic composite material is used for a car. The inorganic filler comprises silane-modified calcium carbonate and nano silicon dioxide, the silane-modified calcium carbonate comprises calcium carbonate surface-treated with silane coupling agent containing alkoxy and unsaturated organic group, and the mass ratio of the silane-modified calcium carbonate to nano silicon dioxide is (4-10):

1. 3.The bacteriostatic polypropylene-based wood-plastic composite material for vehicles according to claim 1, characterized in that, The modified plant fiber satisfies at least one of the following conditions: 1) the plant fiber comprises at least one of bamboo fiber, coconut shell fiber, rice hull fiber and hemp fiber; 2) the weight average molecular weight of the grafting polypropylene is 10000-50000 Da.

4. The wood-plastic composite material according to claim 3, wherein the wood-plastic composite material is used for a car. The preparation method of the modified plant fiber comprises the following steps: S1: mixing 20 parts by mass of grafting polypropylene, 10-60 parts by mass of decalin and 200-400 parts by mass of anhydrous ethanol, heating to 70-80℃, and treating for 30-90 minutes under inert atmosphere to obtain decalin-treated grafting polypropylene; S2: dispersing 10 parts by mass of decalin-treated grafting polypropylene, 0.1-0.5 parts by mass of BPO and 2-4 parts by mass of acrylic acid in 20-40 parts by mass of water, and reacting for 3-4 hours at 60-90℃ under inert atmosphere to obtain PP-g-PAA graft polymer; S3: dispersing 10 parts by mass of the PP-g-PAA graft polymer, 15-30 parts by mass of the plant fiber, and 1-3 parts by mass of acetic acid and 0.1-1 part by mass of 4A molecular sieve in 50-120 parts by mass of dimethyl sulfoxide, and reacting at 60-90°C for 1-3 hours to obtain the plant fiber grafted with the graft polymer; S4: dispersing 15 parts by mass of the plant fiber grafted with the graft polymer and 1-5 parts by mass of zinc pyrithione in 20-60 parts by mass of anhydrous ethanol, and treating at 30-60°C for 2-3 hours to obtain the plant fiber grafted with the graft polymer and having antibacterial function; S5: dispersing 15 parts by mass of the plant fiber grafted with the graft polymer and having antibacterial function and 1-5 parts by mass of a high-molecular-weight hindered amine light stabilizer containing N-H bond in 50-150 parts by mass of anhydrous ethanol, and treating at 30-60°C for 3-6 hours to obtain the plant fiber grafted with the graft polymer and having antibacterial and ultraviolet-resistant functions, as the modified plant fiber.

5. The wood-plastic composite material according to claim 1, wherein the wood-plastic composite material is used for a car. The raw materials satisfy at least one of the following conditions: 1) the weight average molecular weight of the polypropylene matrix is 100000-300000 Da; 2) the lubricant comprises at least one of zinc stearate, magnesium stearate, and calcium stearate; 3) the antioxidant comprises at least one of antioxidant 1010, antioxidant 1076, and antioxidant 168.

6. A method for preparing a bacteriostatic polypropylene-based wood plastic composite for vehicle, characterized in that, The raw materials for the antibacterial polypropylene-based wood-plastic composite material for vehicles according to any one of claims 1-5 are provided. The raw materials are mixed and melt-extruded to obtain the antibacterial polypropylene-based wood-plastic composite material for vehicles. The antibacterial polypropylene-based wood-plastic composite material for vehicles according to any one of claims 1-5 or prepared by the method according to claim 6 is provided.

7. A plastic article for automotive use, characterized by ​

Images