A straw fiber modified wood plastic composite material

Abstract

The present invention relates to the technical field of polymer composite materials, and specifically discloses a straw fiber modified wood plastic composite material. In the present invention, the straw fiber modified wood plastic composite material includes the following raw materials in parts by mass: 100 parts of polypropylene resin, 25-35 parts of flame retardant modified straw fiber, 3-5 parts of maleic anhydride grafted polypropylene, 12-20 parts of synergist, 1-3 parts of antibacterial agent, 1-1.5 parts of stabilizer and 1-3 parts of lubricant, wherein the flame retardant modified straw fiber is prepared from straw fiber powder, basalt fiber and organic flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and the straw fiber renewable resources are recycled in the present invention, which improves its added value and has significant ecological and environmental benefits. Through chemical grafting, each raw material has good dispersibility and compatibility, and the obtained composite material exhibits excellent mechanical properties and flame retardant properties.

Description

Technical Field

[0001] The invention relates to the technical field of polymer composite materials, in particular to a straw fiber modified wood-plastic composite material. Background Art

[0002] Wood plastic composite materials are a new type of composite materials that have been booming in recent years and are widely used in the construction industry, furniture manufacturing, decoration industry, etc. Wood plastic composite materials are mainly made of biomass fibers such as wood powder, rice husks, straw fibers, and polymer plastics such as polyethylene, polypropylene, polyvinyl chloride, and related additives. They have good processing performance, adjustability, and a long service life. They can utilize waste polymer plastics and make full use of waste fiber resources. At the same time, they can be recycled and processed. They are a new type of green and environmentally friendly material with a wide market.

[0003] Chinese patent CN103435882B discloses a thermoplastic wood-plastic composite material and a production method thereof, which includes the following mass percentages: 20-70% plant fiber; 20-70% plastic; 5-25% biomass power plant ash or biomass oil plant ash; 1-10% additives, which realizes the resource utilization of waste. The obtained wood-plastic composite material has good mechanical properties and weather resistance, but the activation effect on plant fiber is not obvious, and the modification effect is not significant. At the same time, uneven dispersion is prone to occur between raw materials, and the interface stress transfer is poor, resulting in poor mechanical properties of the material. Chinese patent application CN105602157A discloses a wood plastic floor, including the following raw materials in parts by weight: 80-100 parts of PVC, 60-100 parts of wood material, 20-40 parts of light calcium carbonate, 1-2 parts of foaming agent, 4.5-5.5 parts of stabilizer, 2.5-3.5 parts of lubricant, 5-8 parts of chlorinated polyethylene, 0.5-2 parts of plasticizer, 0.5-1.5 parts of expander, and 1-1.5 parts of antioxidant; the wood material is rice bran powder and wood powder, and the wood plastic floor is not easy to deform and has low production cost. However, the use of rice bran powder and wood powder as reinforcing materials has a much lower reinforcing effect on the material than fibrous wood materials, and the mechanical properties of the material are poor, and there is a lot of room for improvement. However, the raw materials used in wood plastic composite materials are all combustible or flammable materials, which makes it easy to burn and has poor flame retardant properties. At the same time, PVC wood plastic boards will produce a lot of environmental pollution when burned. Therefore, how to improve the mechanical properties of wood-plastic composites and have good flame retardant properties has become an urgent problem to be solved in the development of wood-plastic composites. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a straw fiber modified wood-plastic composite material, which solves the problems of general mechanical properties and poor flame retardant properties of the wood-plastic composite material.

[0005] In order to achieve the above object, the present invention discloses a straw fiber modified wood plastic composite material, comprising the following raw materials in parts by weight: 100 parts of polypropylene resin, 25-35 parts of flame retardant modified straw fiber, 3-5 parts of maleic anhydride grafted polypropylene, 12-20 parts of synergist, 1-3 parts of antibacterial agent, 1-1.5 parts of stabilizer and 1-3 parts of lubricant;

[0006] The straw fiber modified wood-plastic composite material is prepared by the following steps:

[0007] The polypropylene resin, flame retardant modified straw fiber, maleic anhydride grafted polypropylene, synergist, antibacterial agent, stabilizer and lubricant are mixed uniformly according to the mass parts, placed in a twin-screw extruder, melt blended, extruded, granulated, placed in a flat vulcanizer for hot pressing, and cooled to obtain a straw fiber modified wood-plastic composite material;

[0008] The temperature of melt blending in the twin-screw extruder is 140-170°C, and the screw speed of the extruder is 15-18r / min;

[0009] The temperature of the hot pressing molding is 170-180° C., the time of the hot pressing molding is 8-10 min, and during the hot pressing molding process, the molding pressure is 8 MPa, and the molding time is 15 min.

[0010] Preferably, the flame retardant modified straw fiber is prepared by the following steps:

[0011] S1. Add basalt fiber, 75% ethanol and γ-methacryloxypropyltrimethoxysilane into reaction bottle A, stir and mix, heat to 75-85° C., keep warm for 3-5 hours, filter, wash with deionized water and acetone, and dry to obtain olefin-modified basalt fiber;

[0012] S2, adding straw fiber powder and deionized water into reaction bottle B, stirring and mixing in a nitrogen atmosphere, then adding olefin-modified basalt fiber, glycidyl methacrylate and initiator, heating to 60-70°C, keeping warm for 2-3h, filtering, washing with anhydrous ethanol, and drying to obtain epoxy-modified basalt fiber-straw fiber;

[0013] S3. Add toluene, epoxy-modified basalt fiber-straw fiber, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into reaction bottle C, mix, heat to 100-110°C, keep warm for 6-9h, filter, wash with anhydrous ethanol, and dry to obtain flame-retardant modified straw fiber.

[0014] Preferably, the addition ratio of basalt fiber, 75% ethanol and γ-methacryloxypropyltrimethoxysilane in S1 is 10 g: 120-180 mL: 2-3 g.

[0015] Preferably, the addition ratio of the straw fiber powder, deionized water, olefin-modified basalt fiber, glycidyl methacrylate and initiator in S2 is 10 g: 150-200 mL: 3-5 g: 1-1.5 g: 0.1-0.3 g.

[0016] Furthermore, the straw fiber powder in S2 is prepared from straw fiber under alkali boiling conditions, and the specific steps are as follows: wash and cut the straw fiber, crush it and pass it through a 50-mesh sieve, weigh the straw fiber powder and put it in a beaker, add 10% sodium hydroxide solution at a mass ratio of 1:12, stir and boil it in a 95°C water bath for 2h, wash it with deionized water until it is neutral, and dry it to obtain the straw fiber powder.

[0017] Preferably, the initiator in S2 includes one of benzoyl peroxide, potassium persulfate and ammonium persulfate.

[0018] Preferably, the addition ratio of toluene, epoxy-modified basalt fiber-straw fiber, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in S3 is 100-120 mL: 10 g: 1-3 g.

[0019] Preferably, the synergist is maleic anhydride grafted EPDM rubber.

[0020] Preferably, the antibacterial agent is a benzonitrile compound.

[0021] Preferably, the stabilizer is a calcium-zinc composite stabilizer.

[0022] Preferably, the lubricant is polyethylene wax.

[0023] Beneficial effects of the present invention:

[0024] (1) In the present invention, γ-methacryloxypropyltrimethoxysilane is used to modify basalt fiber, and alkenyl groups are introduced on the surface of basalt fiber to obtain alkenyl-modified basalt fiber. Alkenyl-modified basalt fiber and straw fiber powder and glycidyl methacrylate are grafted and modified under the action of an initiator, and epoxy-modified basalt fiber-straw fiber is obtained after copolymerization, and epoxy groups are introduced. Then, epoxy groups and flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide undergo a ring-opening reaction to obtain flame-retardant modified straw fiber. Flame-retardant modified straw fiber, synergist maleic anhydride grafted EPDM rubber, compatibilizer maleic anhydride grafted polypropylene, antibacterial agent, stabilizer, and lubricant are uniformly mixed to obtain a straw fiber-modified wood-plastic composite board having excellent mechanical properties and flame retardant properties.

[0025] (2) The basalt fiber in the present invention is a new type of inorganic environmentally friendly green high-performance fiber material with multiple excellent properties such as high strength, corrosion resistance, and high temperature resistance. The basalt fiber cooperates with the straw fiber to have good flexural and compressive strength, good mechanical properties and chemical corrosion resistance, and solves the problem of straw recycling at the same time, which is green and environmentally friendly. The dispersibility between the two is improved by graft copolymerization. The two can be evenly dispersed in the polypropylene matrix with excellent compatibility. The hydroxyl groups introduced by epoxy ring opening and the hydroxyl groups on the straw fiber can be esterified with a part of the polar anhydride groups of maleic anhydride grafted EPDM rubber and maleic anhydride grafted polypropylene, and a part of them form hydrogen bonds, which effectively improves the compatibility with the matrix, plays a good volume expansion effect, has a good interface adhesion, reconstructs the molecular structure of the composite material, improves the brittleness and strength of the composite material, and makes the composite material have good toughness and mechanical strength, so as to broaden the application range of the composite material. The flexible EPDM rubber itself has good compatibility with the polypropylene plastic matrix. The added maleic anhydride grafted EPDM rubber will introduce a flexible interface layer at the interface between the straw fiber and the polypropylene plastic matrix. This flexible interface layer enhances the interfacial bonding between the straw fiber and the polypropylene matrix, so that the external force can be effectively transmitted in the plastic matrix through the straw fiber, thereby achieving the purpose of enhancement.

[0026] (3) The flame-retardant modified straw fibers in the present invention are uniformly dispersed in the polypropylene matrix to form a uniform cross-linked network, which effectively improves the flame retardant properties of the matrix. The phosphorus element contained in the introduced flame retardant can promote the matrix to generate substances such as phosphoric acid during combustion, promote the formation of a carbon layer on the surface of the matrix, and capture free radicals in the combustion reaction to terminate the combustion chain reaction. The introduced silane can promote the material to form a continuous and dense carbon layer during pyrolysis, which can effectively isolate oxygen and heat, and inhibit the diffusion of gas products, thereby improving the thermal stability of the matrix material and further improving the flame retardant properties of the matrix. The resulting composite material has excellent flame retardant properties.

[0027] (4) The alkalization treatment of the straw fiber in the present invention is beneficial to the modification of the plant fiber and can dissolve the small molecules of impurities in the straw fiber, so that some low-molecular impurities such as pectin, lignin and hemicellulose in the straw fiber are dissolved and removed, making the surface of the plant fiber rough and enhancing the bonding ability between the straw fiber and the plastic matrix interface; it can open the hydrogen bonds on the surface of the straw fiber, making the fiber surface loose and forming many cavities. These cavities enhance the "locking force" between the polymer matrix and the straw fiber filler, and recycle the straw fiber renewable resources to improve its added value, which has significant ecological and environmental benefits. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The raw materials can be obtained from public commercial channels unless otherwise specified.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] Example 1

[0031] A straw fiber modified wood-plastic composite material comprises the following raw materials in parts by weight: 100 parts of polypropylene resin, 25 parts of flame retardant modified straw fiber, 3 parts of maleic anhydride grafted polypropylene, 12 parts of synergist, 1 part of antibacterial agent, 1 part of stabilizer and 1 part of lubricant polyethylene wax;

[0032] The straw fiber modified wood plastic composite material is prepared by the following steps:

[0033] The polypropylene resin, flame retardant modified straw fiber, maleic anhydride grafted polypropylene, synergist, antibacterial agent, stabilizer and lubricant are uniformly mixed according to the mass parts, placed in a twin-screw extruder, melt blended, the melt blending temperature is 140°C, the screw speed of the extruder is 18r / min, extruded, granulated, and then placed on a flat vulcanizer for hot pressing molding, the hot pressing molding temperature is 170°C, the hot pressing molding time is 10min, the hot pressing molding process, the molding pressure is 8MPa, the molding time is 15min, and cooled to obtain a straw fiber modified wood-plastic composite material.

[0034] The flame retardant modified straw fiber is prepared by the following steps:

[0035] S1. Add 10 g of basalt fiber, 120 mL of 75% ethanol, and 2 g of γ-methacryloxypropyltrimethoxysilane into reaction bottle A, stir and mix, heat to 75° C., keep warm for 5 h, filter, wash with deionized water and acetone, and dry to obtain olefin-modified basalt fiber;

[0036] S2, add 10g of straw fiber powder and 150mL of deionized water into reaction bottle B, stir and mix in a nitrogen atmosphere, then add 3g of olefin-modified basalt fiber, 1g of glycidyl methacrylate and 0.1g of initiator benzoyl peroxide, heat to 60°C, keep warm for 3h, filter, wash with anhydrous ethanol, and dry to obtain epoxy-modified basalt fiber-straw fiber;

[0037] S3. Add 100 mL of toluene, 10 g of epoxy-modified basalt fiber-straw fiber, and 1 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into reaction bottle C, mix, heat to 100 ° C, keep warm for 9 hours, filter, wash with anhydrous ethanol, and dry to obtain flame-retardant modified straw fiber.

[0038] Example 2

[0039] A straw fiber modified wood-plastic composite material, comprising the following raw materials in parts by weight: 100 parts of polypropylene resin, 28 parts of flame retardant modified straw fiber, 3.5 parts of maleic anhydride grafted polypropylene, 15 parts of synergist, 1.8 parts of antibacterial agent, 1.2 parts of stabilizer and 1.8 parts of lubricant polyethylene wax;

[0040] The straw fiber modified wood plastic composite material is prepared by the following steps:

[0041] The polypropylene resin, flame retardant modified straw fiber, maleic anhydride grafted polypropylene, synergist, antibacterial agent, stabilizer and lubricant are mixed uniformly according to the mass parts, placed in a twin-screw extruder, melt blended, the melt blending temperature is 150° C., the screw speed of the extruder is 16 r / min, extruded, granulated, and then placed on a flat vulcanizer for hot pressing molding, the hot pressing molding temperature is 175° C., the hot pressing molding time is 9 minutes, the molding pressure is 8 MPa, the molding time is 15 minutes, and cooled to obtain a straw fiber modified wood-plastic composite material.

[0042] The flame retardant modified straw fiber is prepared by the following steps:

[0043] S1. Add 10 g of basalt fiber, 140 mL of 75% ethanol, and 2.4 g of γ-methacryloxypropyltrimethoxysilane into reaction bottle A, stir and mix, heat to 80° C., keep warm for 4 h, filter, wash with deionized water and acetone, and dry to obtain olefin-modified basalt fiber;

[0044] S2, add 10g of straw fiber powder and 165mL of deionized water into reaction bottle B, stir and mix in a nitrogen atmosphere, then add 3.6g of olefin-modified basalt fiber, 1.2g of glycidyl methacrylate and 0.15g of initiator benzoyl peroxide, heat to 65°C, keep warm for 2.5h, filter, wash with anhydrous ethanol, and dry to obtain epoxy-modified basalt fiber-straw fiber;

[0045] S3. Add 105 mL of toluene, 10 g of epoxy-modified basalt fiber-straw fiber, and 1.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into reaction bottle C, mix, heat to 105°C, keep warm for 7 hours, filter, wash with anhydrous ethanol, and dry to obtain flame-retardant modified straw fiber.

[0046] Example 3

[0047] A straw fiber modified wood-plastic composite material, comprising the following raw materials in parts by weight: 100 parts of polypropylene resin, 32 parts of flame retardant modified straw fiber, 4.5 parts of maleic anhydride grafted polypropylene, 18 parts of synergist, 2.5 parts of antibacterial agent, 1.4 parts of stabilizer and 2.5 parts of lubricant polyethylene wax;

[0048] The straw fiber modified wood plastic composite material is prepared by the following steps:

[0049] The polypropylene resin, flame retardant modified straw fiber, maleic anhydride grafted polypropylene, synergist, antibacterial agent, stabilizer and lubricant are uniformly mixed according to the mass parts, placed in a twin-screw extruder, melt blended, the melt blending temperature is 160° C., the screw speed of the extruder is 17 r / min, extruded, granulated, and then placed on a flat vulcanizer for hot pressing molding, the hot pressing molding temperature is 175° C., the hot pressing molding time is 9 minutes, the molding pressure is 8 MPa, the molding time is 15 minutes, and cooled to obtain a straw fiber modified wood-plastic composite material.

[0050] The flame retardant modified straw fiber is prepared by the following steps:

[0051] S1. Add 10 g of basalt fiber, 160 mL of 75% ethanol, and 2.8 g of γ-methacryloxypropyltrimethoxysilane into reaction bottle A, stir and mix, heat to 80° C., keep warm for 4 h, filter, wash with deionized water and acetone, and dry to obtain olefin-modified basalt fiber;

[0052] S2, add 10g of straw fiber powder and 180mL of deionized water into reaction bottle B, stir and mix in a nitrogen atmosphere, then add 4.5g of olefin-modified basalt fiber, 1.4g of glycidyl methacrylate and 0.25g of initiator benzoyl peroxide, heat to 65°C, keep warm for 2.5h, filter, wash with anhydrous ethanol, and dry to obtain epoxy-modified basalt fiber-straw fiber;

[0053] S3. Add 115 mL of toluene, 10 g of epoxy-modified basalt fiber-straw fiber, and 2.4 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into reaction bottle C, mix, heat to 105°C, keep warm for 8 hours, filter, wash with anhydrous ethanol, and dry to obtain flame-retardant modified straw fiber.

[0054] Example 4

[0055] A straw fiber modified wood plastic composite material, comprising the following raw materials in parts by weight: 100 parts of polypropylene resin, 35 parts of flame retardant modified straw fiber, 5 parts of maleic anhydride grafted polypropylene, 20 parts of synergist, 3 parts of antibacterial agent, 1.5 parts of stabilizer and 3 parts of lubricant polyethylene wax;

[0056] The straw fiber modified wood plastic composite material is prepared by the following steps:

[0057] The polypropylene resin, flame retardant modified straw fiber, maleic anhydride grafted polypropylene, synergist, antibacterial agent, stabilizer and lubricant are mixed uniformly according to the mass parts, placed in a twin-screw extruder, melt blended, the melt blending temperature is 170°C, the screw speed of the extruder is 15r / min, extruded, granulated, and then placed on a flat vulcanizer for hot pressing molding, the hot pressing molding temperature is 180°C, the hot pressing molding time is 8min, the hot pressing molding process, the molding pressure is 8MPa, the molding time is 15min, and cooled to obtain a straw fiber modified wood-plastic composite material.

[0058] The flame retardant modified straw fiber is prepared by the following steps:

[0059] S1. Add 10 g of basalt fiber, 180 mL of 75% ethanol, and 3 g of γ-methacryloxypropyltrimethoxysilane into reaction bottle A, stir and mix, heat to 85° C., keep warm for 3 h, filter, wash with deionized water and acetone, and dry to obtain olefin-modified basalt fiber;

[0060] S2, add 10g of straw fiber powder and 200mL of deionized water into reaction bottle B, stir and mix in a nitrogen atmosphere, then add 5g of olefin-modified basalt fiber, 1.5g of glycidyl methacrylate and 0.3g of initiator benzoyl peroxide, heat to 70°C, keep warm for 2h, filter, wash with anhydrous ethanol, and dry to obtain epoxy-modified basalt fiber-straw fiber;

[0061] S3. Add 120 mL of toluene, 10 g of epoxy-modified basalt fiber-straw fiber, and 3 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into reaction bottle C, mix, heat to 110°C, keep warm for 6 hours, filter, wash with anhydrous ethanol, and dry to obtain flame-retardant modified straw fiber.

[0062] Comparative Example 1

[0063] A straw fiber modified wood plastic composite material, comprising the following raw materials in parts by weight: 100 parts of polypropylene resin, 32 parts of epoxy modified basalt fiber-straw fiber, 4.5 parts of maleic anhydride grafted polypropylene, 18 parts of synergist, 2.5 parts of antibacterial agent, 1.4 parts of stabilizer and 2.5 parts of lubricant polyethylene wax;

[0064] The straw fiber modified wood plastic composite material is prepared by the following steps:

[0065] The polypropylene resin, epoxy modified basalt fiber-straw fiber, maleic anhydride grafted polypropylene, synergist, antibacterial agent, stabilizer and lubricant are mixed uniformly according to the mass parts, placed in a twin-screw extruder, melt blended, the melt blending temperature is 160° C., the screw speed of the extruder is 17 r / min, extruded, granulated, and then placed on a flat vulcanizer for hot pressing molding, the hot pressing molding temperature is 175° C., the hot pressing molding time is 9 minutes, and during the hot pressing molding process, the molding pressure is 8 MPa, the molding time is 15 minutes, and cooled to obtain a straw fiber modified wood-plastic composite material.

[0066] The epoxy-modified basalt fiber-straw fiber is prepared by the following steps:

[0067] S1. Add 10 g of basalt fiber, 160 mL of 75% ethanol, and 2.8 g of γ-methacryloxypropyltrimethoxysilane into reaction bottle A, stir and mix, heat to 80° C., keep warm for 4 h, filter, wash with deionized water and acetone, and dry to obtain olefin-modified basalt fiber;

[0068] S2. Add 10 g of straw fiber powder and 180 mL of deionized water into reaction bottle B, stir and mix in a nitrogen atmosphere, then add 4.5 g of olefin-modified basalt fiber, 1.4 g of glycidyl methacrylate and 0.25 g of initiator benzoyl peroxide, heat to 65 ° C, keep warm for 2.5 h, filter, wash with anhydrous ethanol, and dry to obtain epoxy-modified basalt fiber-straw fiber.

[0069] Comparative Example 2

[0070] A straw fiber modified wood-plastic composite material, comprising the following raw materials in parts by weight: 100 parts of polypropylene resin, 18 parts of straw fiber powder, 8 parts of basalt fiber, 6 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 4.5 parts of maleic anhydride grafted polypropylene, 18 parts of a synergist, 2.5 parts of an antibacterial agent, 1.4 parts of a stabilizer, and 2.5 parts of a lubricant polyethylene wax;

[0071] The straw fiber modified wood plastic composite material is prepared by the following steps:

[0072] The polypropylene resin, straw fiber powder, basalt fiber, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, maleic anhydride grafted polypropylene, synergist, antibacterial agent, stabilizer and lubricant are mixed uniformly according to the mass parts, placed in a twin-screw extruder, melt blended, the melt blending temperature is 160° C., the screw speed of the extruder is 17 r / min, extruded, granulated, and then placed on a flat vulcanizer for hot pressing molding, the hot pressing molding temperature is 175° C., the hot pressing molding time is 9 minutes, the hot pressing molding process, the molding pressure is 8 MPa, the molding time is 15 minutes, and cooled to obtain a straw fiber modified wood-plastic composite material.

[0073] Comparative Example 3

[0074] A straw fiber modified wood plastic composite material comprises the following raw materials in parts by weight: 122.5 parts of polypropylene resin, 32 parts of flame retardant modified straw fiber, 2.5 parts of antibacterial agent, 1.4 parts of stabilizer and 2.5 parts of lubricant polyethylene wax;

[0075] The straw fiber modified wood plastic composite material is prepared by the following steps:

[0076] The polypropylene resin, flame retardant modified straw fiber, antibacterial agent, stabilizer and lubricant are mixed uniformly according to the mass parts, placed in a twin-screw extruder, melt blended, the melt blending temperature is 160° C., the screw speed of the extruder is 17 r / min, extruded, granulated, and then placed on a flat vulcanizer for hot pressing molding, the hot pressing molding temperature is 175° C., the hot pressing molding time is 9 min, during the hot pressing molding process, the molding pressure is 8 MPa, the molding time is 15 min, and cooled to obtain a straw fiber modified wood-plastic composite material.

[0077] The preparation process of the flame retardant modified straw fiber is the same as that in Example 3.

[0078] The polypropylene used in the embodiments of the present invention and the comparative examples was purchased from PetroChina Daqing Petrochemical Company, model T30S; maleic anhydride grafted polypropylene was purchased from Shanghai Rizhisheng New Technology Development Co., Ltd., model CMG9801; the straw fiber is wheat straw fiber (WSF), purchased from Shaanxi Jinhe Agricultural Technology Co., Ltd., and is industrial grade; basalt fiber was purchased from Zhejiang Shijin Basalt Fiber Co., Ltd., with a length of 6 mm and a diameter of 13 μm; maleic anhydride grafted ethylene propylene diene monomer rubber (EPDM-MA) was purchased from Ningbo Nengzhiguang New Materials Technology Co., Ltd., with a brand name of GPM512; the antibacterial agent is a commercially available antibacterial agent of model RHA-MT1; the stabilizer was purchased from Shenzhen Sende Plastic Additive Co., Ltd., and is a CZX768 calcium zinc stabilizer; the lubricant polyethylene wax was purchased from Dongguan Shanyi Plastic Co., Ltd., with a brand name of Thailand SCG and a product number of LP0020P; other unspecified reagents are all commercially available.

[0079] The straw fiber modified wood plastic composite materials in Examples 1-4 and Comparative Examples 1-3 were tested for relevant properties, as follows:

[0080] (1) Mechanical properties test: Referring to GB / T1447-2005 "Test method for tensile properties of fiber reinforced plastics", the tensile strength test of the samples was carried out using a HZ-1009A universal tensile testing machine, the test speed was 10 mm / min, and 3 samples were measured in each group and the average value was taken; referring to GB / T1449-2005 "Test method for bending properties of fiber reinforced plastics", the bending properties of the samples were tested using an XWW microcomputer-controlled electronic universal testing machine, the test speed was 2 mm / min, the span was 64 mm, and 3 samples were measured in each group and the average value was taken; the test results are shown in Table 1:

[0081] Table 1

[0082]

[0083] According to the test results in Table 1, it can be seen that the straw fiber modified wood plastic composite materials corresponding to Examples 1-4 have excellent mechanical properties. The tensile strength of the sample corresponding to Example 3 is 39.3MPa, and the bending strength of the sample corresponding to Example 4 is 48.5MPa. In Comparative Example 1, epoxy-modified basalt fiber-straw fiber was directly added, and no organic flame retardant was added for flame retardant modification, and the mechanical properties were improved. In Comparative Example 2, straw fiber powder, basalt fiber, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were directly added, and the dispersibility and compatibility of the raw materials were greatly reduced, and the mechanical properties were reduced. The tensile strength of the corresponding sample was 31.2MPa and the bending strength was 34.1MPa. In Comparative Example 3, maleic anhydride grafted polypropylene and synergist were not added, and the mechanical properties were greatly reduced. The tensile strength of the corresponding sample was 30.5MPa and the bending strength was 31.3MPa.

[0084] (2) Flame retardant performance test: The samples were tested for limiting oxygen index according to the test method of GB / T2406.1-2008 "Determination of combustion behavior of plastics by oxygen index method". Three samples were measured in each group and the average value was taken. The test results are shown in Table 2:

[0085] Table 2

[0086]

[0087] According to the test results in Table 2, it can be seen that the straw fiber modified wood plastic composite materials corresponding to Examples 1-4 have excellent flame retardant properties, and the corresponding limiting oxygen index is greater than 27%. The limiting oxygen index of the sample corresponding to Example 4 is 30.7%. In Comparative Example 1, epoxy modified basalt fiber-straw fiber was directly added, and no organic flame retardant was added for flame retardant modification, and the flame retardant performance was greatly reduced, and the limiting oxygen index of the corresponding sample was 24.2%. In Comparative Example 2, straw fiber powder, basalt fiber, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were directly added, and the dispersibility and compatibility of the raw materials were greatly reduced, which had a certain effect on the flame retardant performance, and the limiting oxygen index of the corresponding sample was 27.6%. In Comparative Example 3, maleic anhydride grafted polypropylene and synergist were not added, which had little effect on the flame retardant performance, and the limiting oxygen index of the corresponding sample was 30.3%.

[0088] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that all equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A straw fiber modified wood-plastic composite material, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of polypropylene resin, 25-35 parts of flame retardant modified straw fiber, 3-5 parts of maleic anhydride grafted polypropylene, 12-20 parts of synergist, 1-3 parts of antibacterial agent, 1-1.5 parts of stabilizer and 1-3 parts of lubricant; The straw fiber modified wood-plastic composite material is prepared by the following steps: The polypropylene resin, flame retardant modified straw fiber, maleic anhydride grafted polypropylene, synergist, antibacterial agent, stabilizer and lubricant are mixed uniformly according to the mass parts, placed in a twin-screw extruder, melt blended, extruded, granulated, placed in a flat vulcanizer for hot pressing, and cooled to obtain a straw fiber modified wood-plastic composite material; The temperature of melt blending in the twin-screw extruder is 140-170°C, and the screw speed of the extruder is 15-18r / min; The temperature of the hot pressing molding is 170-180°C, the time of the hot pressing molding is 8-10 minutes, the molding pressure is 8MPa, and the molding time is 15 minutes during the hot pressing molding process; The flame retardant modified straw fiber is prepared by the following steps: S1. Add basalt fiber, 75% ethanol and γ-methacryloxypropyltrimethoxysilane into reaction bottle A, stir and mix, heat to 75-85° C., keep warm for 3-5 hours, filter, wash with deionized water and acetone, and dry to obtain olefin-modified basalt fiber; S2, adding straw fiber powder and deionized water into reaction bottle B, stirring and mixing in a nitrogen atmosphere, then adding olefin-modified basalt fiber, glycidyl methacrylate and initiator, heating to 60-70°C, keeping warm for 2-3h, filtering, washing with anhydrous ethanol, and drying to obtain epoxy-modified basalt fiber-straw fiber; S3, adding toluene, epoxy-modified basalt fiber-straw fiber, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into reaction bottle C, mixing, heating to 100-110° C., keeping warm for 6-9 hours, filtering, washing with anhydrous ethanol, and drying to obtain flame-retardant modified straw fiber; The synergist is maleic anhydride grafted EPDM rubber.

2. The straw fiber modified wood plastic composite material according to claim 1, characterized in that: The addition ratio of basalt fiber, 75% ethanol, and γ-methacryloxypropyltrimethoxysilane in S1 is 10 g: 120-180 mL: 2-3 g.

3. The straw fiber modified wood plastic composite material according to claim 1, characterized in that: The addition ratio of the straw fiber powder, deionized water, olefin-modified basalt fiber, glycidyl methacrylate and initiator in the S2 is 10 g: 150-200 mL: 3-5 g: 1-1.5 g: 0.1-0.3 g.

4. The straw fiber modified wood plastic composite material according to claim 1, characterized in that: The initiator in S2 includes one of benzoyl peroxide, potassium persulfate and ammonium persulfate.

5. The straw fiber modified wood plastic composite material according to claim 1, characterized in that: The addition ratio of toluene, epoxy-modified basalt fiber-straw fiber, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in the S3 is 100-120 mL: 10 g: 1-3 g.

6. The straw fiber modified wood plastic composite material according to claim 1, characterized in that: The antibacterial agent is a benzonitrile compound.

7. The straw fiber modified wood plastic composite material according to claim 1, characterized in that: The stabilizer is a calcium-zinc composite stabilizer.

8. The straw fiber modified wood plastic composite material according to claim 1, characterized in that: The lubricant is polyethylene wax.

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