Biomass-based fiber modified composite material and preparation method thereof

Abstract

The invention discloses a biomass-based fiber modified composite material and a preparation method thereof, and belongs to the technical field of composite materials, the biomass-based fiber modified composite material comprises the following raw materials by weight: 100 parts of polyolefin resin and 20-50 parts of modified fiber, the modified fibers are obtained by treating wood fibers, wherein the wood fibers are pretreated by dopamine to obtain dopamine pretreated fibers, and then nano silicon dioxide is deposited on the surfaces of the dopamine pretreated fibers to obtain the modified fibers. The preparation method of the composite material comprises the following steps: mixing the raw materials to obtain a primary mixture, carrying out melt blending extrusion granulation on the primary mixture in a double-screw extruder, and finally carrying out injection molding on the obtained granules to obtain the biomass-based fiber modified composite material. Through the synergistic effect of dopamine treatment and silicon dioxide deposition, the interface bonding performance between the fiber and a polyolefin matrix can be remarkably enhanced, stress transfer is more efficient, and therefore the mechanical property of the composite material is improved optimally.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and particularly relates to a biomass-based fiber modified composite material and a preparation method thereof. Background Art

[0002] In recent years, polymer composite materials have been widely used in the fields of packaging, construction, automobiles, etc. due to their excellent properties. By adding fiber reinforcement phases to matrix materials such as polypropylene (PP) and polyethylene (PE), the mechanical properties, thermal stability, and dimensional stability of the composite materials can be significantly improved. Traditional reinforcing fibers are mainly divided into two categories: synthetic fibers and natural fibers. Among them, synthetic fibers, such as carbon fibers, mainly come from petroleum resources (the main precursors of carbon fibers are polyacrylonitrile (PAN) or pitch, both of which rely on petroleum: PAN-based carbon fibers: polyacrylonitrile (PAN) is polymerized from acrylonitrile, and acrylonitrile is a product of petroleum refining (prepared by the acrylonitrile ammoxidation method); pitch-based carbon fibers: the raw materials come from petroleum or coal tar pitch, which are petrochemical by-products). Although they have advantages such as high strength and high modulus, their production process has high energy consumption and high cost, and it is difficult to degrade naturally after being discarded, which not only exacerbates the problem of petrochemical resource depletion but also causes serious environmental problems such as "white pollution". In contrast, natural fibers (such as hemp fibers, bamboo fibers, coconut shell fibers, etc.) have shown great potential in the field of environmentally friendly composite materials due to their wide sources, renewable nature, and biodegradability. Natural fiber-reinforced polymer composite materials not only have environmental-friendly characteristics but also have advantages such as light weight, high strength, low processing energy consumption, and high cost-effectiveness, which conform to the current concept of sustainable development and have become a research hotspot in the field of green materials. Especially with the increasingly strict environmental protection regulations and the improvement of consumers' environmental protection awareness, the development of high-performance natural fiber-reinforced polymer composite materials has important economic value and ecological significance.

[0003] Although natural fibers have advantages such as environmental friendliness, renewability, and low cost, there are polarity differences between natural fibers and matrix materials PP / PE. The surface of plant fibers is rich in hydroxyl groups and is hydrophilic, while PP / PE is a non-polar hydrophobic material, resulting in weak interfacial bonding force between the two and affecting the mechanical properties. Moreover, fibers are prone to aggregation during melt processing and are unevenly dispersed, which will also reduce the reinforcement effect. Summary of the Invention

[0004] The purpose of the present invention is to provide a biomass-based fiber modified composite material and a preparation method thereof to solve the problem of poor mechanical properties of the biomass-based fiber modified composite material.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The first aspect of the present application provides a biomass-based fiber modified composite material, which comprises the following raw materials by weight: 100 parts of polyolefin resin and 20-50 parts of modified fiber, and the modified fiber is obtained by treating wood fiber: the wood fiber is pretreated with dopamine to obtain dopamine-pretreated fiber, and then nano-silica is deposited on the surface of the dopamine-pretreated fiber to obtain the modified fiber.

[0007] In some possible implementation manners, the modified fiber is prepared by the following steps:

[0008] Add the wood fiber into the dopamine buffer solution and soak it at room temperature for 16-24h, take it out, wash it with water and dry it to obtain the dopamine-pretreated fiber;

[0009] Mix ethanol, ammonia water with a mass fraction of 25% and water to obtain a mixed solution, immerse the dopamine-pretreated fiber into the mixed solution, slowly add tetraethoxysilane, stir at 50°C for 1-5h, then take it out and dry it at 80°C to obtain the modified fiber.

[0010] In some possible implementation manners, the concentration of dopamine in the dopamine buffer solution is 2-3g / L, the concentration of tris(hydroxymethyl)aminomethane is 1.2g / L, and the pH value is 8.5; the mass ratio of the dosages of ethanol, ammonia water, water and tetraethoxysilane is 6.4-6.5:0.6:1:1.4-1.8.

[0011] In some possible implementation manners, the wood fiber is at least one of plant fibers such as bamboo fiber, wood powder, palm fiber, etc.; the size of the wood fiber is 150-180μm.

[0012] In some possible implementation manners, by weight, the raw materials of the biomass-based fiber modified composite material further include 5-15 parts of a flame retardant, and the flame retardant is lignin-coated ammonium polyphosphate and is made by adding borate to crosslink and modify lignin.

[0013] In some possible implementation manners, the flame retardant is prepared by the following steps:

[0014] Under a nitrogen atmosphere, mix ethanol and ammonium polyphosphate, heat to 75-80°C, add alkali lignin, keep the temperature unchanged, continue to stir for 5-6h, then add borate, ultrasonically disperse at room temperature for 50-60min, and obtain the flame retardant after filtration and drying.

[0015] In some possible implementation manners, the dosage ratio of ethanol, ammonium polyphosphate, alkali lignin and borate is 600mL:25-30g:12-15g:2-6g.

[0016] In some possible implementation manners, the borate is one of amine borate, zinc borate, aluminum borate and magnesium borate.

[0017] In some possible implementation manners, the polyolefin resin is one of polypropylene resin and polyethylene resin.

[0018] The first aspect of the present application provides a method for preparing a biomass-based fiber modified composite material, including the following steps:

[0019] Mix the raw materials to obtain a preliminary mixture, then melt and co-extrude the preliminary mixture on a twin-screw extruder to granulate, and finally injection mold the obtained pellets to obtain the biomass-based fiber modified composite material.

[0020] Advantages of the present invention:

[0021] The present invention provides a biomass-based fiber modified composite material. In this biomass-based fiber modified composite material, modified fibers are added to solve the problem of poor mechanical properties of the biomass-based fiber modified composite material. The modified fiber is obtained by pretreating wood fiber with dopamine to obtain dopamine-pretreated fiber, and then depositing nano-silica on the surface of the dopamine-pretreated fiber to obtain the modified fiber. Through the synergistic effect of dopamine treatment and silica deposition, the interfacial bonding performance between the fiber and the polyolefin matrix can be significantly enhanced, making stress transfer more efficient, and thus showing the best performance in improving the mechanical properties of the composite material. Specific embodiments

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.

[0023] Obviously, the following description is only some examples or embodiments of the present application. For those of ordinary skill in the art, without creative efforts, the present application can also be applied to other similar scenarios. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacturing or production changes based on the technical content disclosed in the present application are only conventional technical means and should not be understood that the content disclosed in the present application is insufficient.

[0024] However, there may be cases where unnecessary details are omitted. For example, there are cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0025] Without special instructions, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0026] The following is a detailed description of a biomass-based fiber modified composite material and its preparation method according to an embodiment of the present application.

[0027] In the first aspect of the embodiment of the present application, a biomass-based fiber modified composite material includes the following raw materials by weight: 100 parts of polyolefin resin and 20 - 50 parts of modified fiber, and the modified fiber is obtained by treating wood fiber: the wood fiber is pretreated with dopamine to obtain dopamine-pretreated fiber, and then nano-silica is deposited on the surface of the dopamine-pretreated fiber to obtain the modified fiber.

[0028] In some specific embodiments, the modified fiber is prepared by the following steps:

[0029] The wood fiber is added to dopamine buffer solution for pretreatment: the wood fiber is added to dopamine buffer solution and soaked at room temperature for 16 - 24 h, taken out, washed with water and dried to obtain dopamine-pretreated fiber;

[0030] The dopamine-pretreated fiber is modified with TEOS (tetraethoxysilane), and nano-silica is deposited on the surface of the dopamine-pretreated fiber by sol-gel method to improve roughness and hydrophobicity:

[0031] Ethanol, ammonia water with a mass fraction of 25%, and water are mixed to obtain a mixed solution. The dopamine-pretreated fiber is immersed in the mixed solution, and tetraethoxysilane is slowly added. At a temperature of 50 °C, after stirring for 1 - 5 h, it is taken out and dried at 80 °C to obtain the modified fiber; the mass ratio of the amounts of ethanol, ammonia water, water, and tetraethoxysilane is 6.4 - 6.5:0.6:1:1.4 - 1.8.

[0032] In some specific embodiments, the concentration of dopamine in the dopamine buffer solution is 2 - 3 g / L, the concentration of tris(hydroxymethyl)aminomethane (Tris) is 1.2 g / L, and the pH value is 8.5.

[0033] In some specific embodiments, the wood fiber is at least one of plant fibers such as bamboo fiber, wood powder, palm fiber, etc.; the size of the wood fiber is 150-180μm.

[0034] In some specific embodiments, by weight, the raw materials of the biomass-based fiber modified composite material further include 5-15 parts of a flame retardant, and the flame retardant is lignin-coated ammonium polyphosphate, which is prepared by adding borate to crosslink and modify lignin, consuming the polar groups in the lignin-coated ammonium polyphosphate, thereby inhibiting lignin agglomeration and improving the dispersibility between the flame retardant and the polyolefin resin.

[0035] In some specific embodiments, the flame retardant is prepared by the following steps:

[0036] In a nitrogen atmosphere, ethanol and ammonium polyphosphate are mixed, heated to 75-80°C, alkali lignin is added, the temperature is kept constant, and stirring is continued for 5-6h, then borate is added, and ultrasonic dispersion is carried out at room temperature for 50-60min, followed by suction filtration and drying to obtain the flame retardant.

[0037] In some specific embodiments, the dosage ratio of ethanol, ammonium polyphosphate, alkali lignin and borate is 600mL: 25-30g: 12-15g: 2-6g.

[0038] In some specific embodiments, the borate is one of ammonium borate, zinc borate, aluminum borate and magnesium borate.

[0039] In some specific embodiments, the polyolefin resin is one of polypropylene resin and polyethylene resin.

[0040] The second aspect of the embodiments of the present application provides a preparation method of a biomass-based fiber modified composite material, including the following steps:

[0041] The raw materials are mixed to obtain a preliminary mixture, and then the preliminary mixture is melt-blended and extruded into pellets by a twin-screw extruder, and finally the obtained pellets are injection-molded to obtain the biomass-based fiber modified composite material.

[0042] The melt-blending and extrusion is set conventionally. For example, the temperature of the twin-screw extruder from the feeding port to the die head is set to 160, 175, 185, 195, 205, 200°C, and the screw speed is 100-150r / min; the temperature of the injection molding machine is set to 210°C in zone 1, 210°C in zone 2, 205°C in zone 3, and 205°C in zone 4.

[0043] The following is specifically described in conjunction with the embodiments.

[0044] Example 1

[0045] This embodiment provides a biomass-based fiber modified composite material, which includes the following raw materials by weight: 100 parts of polypropylene resin (copolypropylene: YPJ–1215C) and 20 parts of modified fibers, and the modified fibers are obtained by treating wood fibers; the modified fibers are prepared through the following steps:

[0046] Add the wood fibers to a dopamine buffer solution and soak them at room temperature for 24 h. After taking them out, wash them with water and dry them to obtain dopamine-pretreated fibers; the concentration of dopamine in the dopamine buffer solution is 2 g / L, the concentration of Tris is 1.2 g / L, and the pH value is 8.5.

[0047] Mix ethanol, 25% by mass ammonia water and water to obtain a mixed solution. Immerse the dopamine-pretreated fibers in the mixed solution, slowly add tetraethoxysilane, and stir at 50 °C for 1 h, then take them out and dry them at 80 °C to obtain modified fibers; the mass ratio of the amounts of ethanol, ammonia water, water and tetraethoxysilane used is 6.4:0.6:1:1.4; the wood fibers are bamboo fibers, and the size of the wood fibers is 150 - 180 μm.

[0048] Mix the raw materials to obtain a preliminary mixture, then melt-blend and extrude the preliminary mixture on a twin-screw extruder to granulate, and finally injection-mold the obtained pellets to obtain the biomass-based fiber modified composite material; the temperature of the twin-screw extruder from the feeding port to the die head is set to 160, 175, 185, 195, 205, 200 °C, and the screw speed is 150 r / min; the temperature of the injection molding machine is set to 210 °C in zone 1, 210 °C in zone 2, 205 °C in zone 3, and 205 °C in zone 4.

[0049] Example 2

[0050] This embodiment provides a biomass-based fiber modified composite material, which includes the following raw materials by weight: 100 parts of polypropylene resin and 30 parts of modified fibers, and the modified fibers are obtained by treating wood fibers; the modified fibers are prepared through the following steps:

[0051] Add the wood fibers to a dopamine buffer solution and soak them at room temperature for 24 h. After taking them out, wash them with water and dry them to obtain dopamine-pretreated fibers; the concentration of dopamine in the dopamine buffer solution is 2 g / L, the concentration of Tris is 1.2 g / L, and the pH value is 8.5.

[0052] Mix ethanol, 25% by mass ammonia water and water to obtain a mixed solution. Immerse the dopamine-pretreated fibers in the mixed solution, slowly add tetraethoxysilane, and stir at 50 °C for 1 h, then take them out and dry them at 80 °C to obtain modified fibers; the mass ratio of the amounts of ethanol, ammonia water, water and tetraethoxysilane used is 6.4:0.6:1:1.4; the wood fibers are bamboo fibers, and the size of the wood fibers is 150 - 180 μm.

[0053] The raw materials are mixed to obtain a preliminary mixture, and then the preliminary mixture is melt-blended and extruded into pellets by a twin-screw extruder. Finally, the obtained pellets are injection-molded to obtain a biomass-based fiber-modified composite material. The temperature of the twin-screw extruder from the feeding port to the die head is set at 160, 175, 185, 195, 205, 200 °C, and the screw speed is 150 r / min. The temperature of the injection molding machine is set at 210 °C in zone 1, 210 °C in zone 2, 205 °C in zone 3, and 205 °C in zone 4.

[0054] Example 3

[0055] This example provides a biomass-based fiber-modified composite material, which includes the following raw materials by weight: 100 parts of polypropylene resin and 40 parts of modified fiber, and the modified fiber is obtained by treating wood fiber; the modified fiber is prepared by the following steps:

[0056] The wood fiber is added to a dopamine buffer solution and soaked at room temperature for 24 h. After taking it out, it is washed with water and dried to obtain dopamine-pretreated fiber. The concentration of dopamine in the dopamine buffer solution is 2 g / L, the concentration of Tris is 1.2 g / L, and the pH value is 8.5.

[0057] Ethanol, 25% ammonia water by mass fraction, and water are mixed to obtain a mixed solution. The dopamine-pretreated fiber is taken and immersed in the mixed solution, and tetraethoxysilane is slowly added. Under the condition of a temperature of 50 °C, after stirring for 1 h, it is taken out and dried at 80 °C to obtain the modified fiber. The mass ratio of the amounts of ethanol, ammonia water, water, and tetraethoxysilane used is 6.4:0.6:1:1.4; the wood fiber is bamboo fiber, and the size of the wood fiber is 150 - 180 μm.

[0058] The raw materials are mixed to obtain a preliminary mixture, and then the preliminary mixture is melt-blended and extruded into pellets by a twin-screw extruder. Finally, the obtained pellets are injection-molded to obtain a biomass-based fiber-modified composite material. The temperature of the twin-screw extruder from the feeding port to the die head is set at 160, 175, 185, 195, 205, 200 °C, and the screw speed is 150 r / min. The temperature of the injection molding machine is set at 210 °C in zone 1, 210 °C in zone 2, 205 °C in zone 3, and 205 °C in zone 4.

[0059] Example 4

[0060] This example provides a biomass-based fiber-modified composite material, which includes the following raw materials by weight: 100 parts of polypropylene resin and 50 parts of modified fiber, and the modified fiber is obtained by treating wood fiber; the modified fiber is prepared by the following steps:

[0061] The wood fibers were added to a dopamine buffer solution and soaked at room temperature for 16 h. After taking them out, they were washed with water and dried to obtain dopamine-pretreated fibers. The concentration of dopamine in the dopamine buffer solution was 2 g / L, the concentration of Tris was 1.2 g / L, and the pH value was 8.5.

[0062] Ethanol, 25% by mass ammonia water, and water were mixed to obtain a mixed solution. The dopamine-pretreated fibers were taken and immersed in the mixed solution, and tetraethoxysilane was slowly added. Under the condition of a temperature of 50 °C, after stirring for 2 h, they were taken out and dried at 80 °C to obtain modified fibers. The mass ratio of the amounts of ethanol, ammonia water, water, and tetraethoxysilane used was 6.5:0.6:1:1.8. The wood fibers were bamboo fibers, and the size of the wood fibers was 150 - 180 μm.

[0063] The raw materials were mixed to obtain a preliminary mixture, and then the preliminary mixture was melt-blended and extruded into pellets by a twin-screw extruder. Finally, the obtained pellets were injection-molded to obtain a biomass-based fiber modified composite material. The temperature of the twin-screw extruder from the feeding port to the die head was set to 160, 175, 185, 195, 205, 200 °C, and the screw speed was 150 r / min. The temperature of the injection molding machine was set to 210 °C in zone 1, 210 °C in zone 2, 205 °C in zone 3, and 205 °C in zone 4.

[0064] Comparative Example 1

[0065] Compared with Example 1, this comparative example was different in the modified fibers: directly depositing silica, that is, not performing dopamine treatment on plant fibers. Ethanol, 25% by mass ammonia water, and water were mixed to obtain a mixed solution. The wood fibers were taken and immersed in the mixed solution, and tetraethoxysilane was slowly added. Under the condition of a temperature of 50 °C, after stirring for 1 h, they were taken out and dried at 80 °C to obtain modified fibers. The mass ratio of the amounts of ethanol, ammonia water, water, and tetraethoxysilane used was 6.4:0.6:1:1.4. The wood fibers were bamboo fibers, and the size of the wood fibers was 150 - 180 μm. The wood fibers were bamboo fibers, and the size of the wood fibers was 150 - 180 μm.

[0066] The remaining raw materials and the preparation process were the same as those in Example 1.

[0067] Comparative Example 2

[0068] Compared with Example 1, this comparative example was different in the modified fibers: using dopamine to treat plant fibers and not performing silica deposition. The wood fibers were added to a dopamine buffer solution and soaked at room temperature for 24 h. After taking them out, they were washed with water and dried to obtain dopamine-pretreated fibers. The concentration of dopamine in the dopamine buffer solution was 2 g / L, the concentration of Tris was 1.2 g / L, and the pH value was 8.5. The wood fibers were bamboo fibers, and the size of the wood fibers was 150 - 180 μm.

[0069] The remaining raw materials and the preparation process are the same as those in Example 1.

[0070] The properties of the composite materials prepared in Examples 1 - 4 and Comparative Examples 1 - 2 were tested. The tensile strength was carried out in accordance with GB / T 1040 at a temperature of 25 °C, a humidity of 50%, and a tensile speed of 50 mm / min. The results are shown in Table 1 below:

[0071] Table 1

[0072]

[0073]

[0074] According to the test results, for the composite material added with the modified fiber of the present invention, poly-dopamine layer can be formed on the surface of the plant fiber by dopamine treatment, and this layer has good adhesion and reactivity. The subsequently deposited silica can further enhance the rigidity and stability of the fiber surface, and the prepared composite material has a relatively high tensile strength. Through the comparison between Example 1 and Comparative Examples 1 - 2, it can be seen that through the synergistic effect of dopamine treatment and silica deposition, the interfacial bonding performance between the fiber and the polyolefin matrix can be significantly enhanced, making the stress transfer more efficient, thus showing the best performance in improving the mechanical properties of the composite material.

[0075] Example 5

[0076] This example provides a biomass-based fiber modified composite material, which includes the following raw materials by weight: 100 parts of polypropylene resin, 20 parts of modified fiber, and 5 parts of flame retardant. The modified fiber is the same as that in Example 1. The flame retardant is prepared through the following steps:

[0077] Under a nitrogen atmosphere, ethanol and ammonium polyphosphate were mixed and heated to 80 °C, then alkali lignin was added. Keeping the temperature unchanged, stirring was continued for 5 h, and then ammonium borate was added. Ultrasonic dispersion was carried out for 60 min at room temperature, and then filtration and drying were carried out to obtain the flame retardant. The dosage ratio of ethanol, ammonium polyphosphate, alkali lignin, and ammonium borate is 600 mL: 25 g: 12 g: 4 g.

[0078] The raw materials were mixed to obtain a preliminary mixture, and then the preliminary mixture was melt-blended and extruded into pellets by a twin-screw extruder. Finally, the obtained pellets were injection-molded to obtain the biomass-based fiber modified composite material. The temperature of the twin-screw extruder from the feeding port to the die head was set to 160, 175, 185, 195, 205, 200 °C, and the screw speed was 150 r / min. The temperature of the injection molding machine was set to 210 °C in zone 1, 210 °C in zone 2, 205 °C in zone 3, and 205 °C in zone 4.

[0079] Example 6

[0080] This embodiment provides a biomass-based fiber modified composite material, which includes the following raw materials by weight: 100 parts of polypropylene resin, 20 parts of modified fiber, and 10 parts of flame retardant. The modified fiber is the same as that in Example 1. The flame retardant is prepared through the following steps:

[0081] Under a nitrogen atmosphere, ethanol and ammonium polyphosphate are mixed and heated to 80 °C. Alkali lignin is added, and the temperature is kept constant while stirring continues for 5 h. Then, ammonium borate is added, and ultrasonic dispersion is carried out at room temperature for 60 min. After filtration and drying, the flame retardant is obtained; the dosage ratio of ethanol, ammonium polyphosphate, alkali lignin, and ammonium borate is 600 mL: 25 g: 12 g: 4 g.

[0082] The raw materials are mixed to obtain a preliminary mixture, and then the preliminary mixture is melt-blended and extruded into pellets by a twin-screw extruder. Finally, the obtained pellets are injection-molded to obtain the biomass-based fiber modified composite material; the temperature of the twin-screw extruder from the feeding port to the die head is set to 160, 175, 185, 195, 205, 200 °C, and the screw speed is 150 r / min; the temperature of the injection molding machine is set to 210 °C in zone 1, 210 °C in zone 2, 205 °C in zone 3, and 205 °C in zone 4.

[0083] Example 7

[0084] This embodiment provides a biomass-based fiber modified composite material, which includes the following raw materials by weight: 100 parts of polypropylene resin, 20 parts of modified fiber, and 15 parts of flame retardant. The modified fiber is the same as that in Example 1. The flame retardant is prepared through the following steps:

[0085] Under a nitrogen atmosphere, ethanol and ammonium polyphosphate are mixed and heated to 80 °C. Alkali lignin is added, and the temperature is kept constant while stirring continues for 5 h. Then, ammonium borate is added, and ultrasonic dispersion is carried out at room temperature for 60 min. After filtration and drying, the flame retardant is obtained; the dosage ratio of ethanol, ammonium polyphosphate, alkali lignin, and ammonium borate is 600 mL: 25 g: 12 g: 4 g.

[0086] The raw materials are mixed to obtain a preliminary mixture, and then the preliminary mixture is melt-blended and extruded into pellets by a twin-screw extruder. Finally, the obtained pellets are injection-molded to obtain the biomass-based fiber modified composite material; the temperature of the twin-screw extruder from the feeding port to the die head is set to 160, 175, 185, 195, 205, 200 °C, and the screw speed is 150 r / min; the temperature of the injection molding machine is set to 210 °C in zone 1, 210 °C in zone 2, 205 °C in zone 3, and 205 °C in zone 4.

[0087] Example 8

[0088] This embodiment provides a biomass-based fiber modified composite material, which includes the following raw materials by weight: 100 parts of polypropylene resin, 20 parts of modified fiber, and 10 parts of flame retardant. The modified fiber is the same as that in Example 1. The flame retardant is prepared through the following steps:

[0089] Under a nitrogen atmosphere, ethanol and ammonium polyphosphate are mixed and heated to 80°C. Alkali lignin is added, and the temperature is kept constant while stirring continues for 5 hours. Then, aluminum borate is added, and ultrasonic dispersion is carried out at room temperature for 60 minutes. After filtration and drying, the flame retardant is obtained. The dosage ratio of ethanol, ammonium polyphosphate, alkali lignin, and aluminum borate is 600 mL: 25 g: 12 g: 4 g.

[0090] The raw materials are mixed to obtain a preliminary mixture, and then the preliminary mixture is melt-blended and extruded into pellets by a twin-screw extruder. Finally, the obtained pellets are injection-molded to obtain the biomass-based fiber modified composite material. The temperature of the twin-screw extruder from the feeding port to the die head is set at 160, 175, 185, 195, 205, 200°C, and the screw speed is 150 r / min. The temperature of the injection molding machine is set at 210°C in zone 1, 210°C in zone 2, 205°C in zone 3, and 205°C in zone 4.

[0091] Comparative Example 3

[0092] Compared with Example 5, the difference in this comparative example is that the modified fiber is replaced with the fiber in Comparative Example 2, and the remaining raw materials and preparation process are the same as those in Example 5.

[0093] Comparative Example 4

[0094] Compared with Example 5, the difference in this comparative example is that the modified fiber is replaced with the fiber in Comparative Example 3, and the remaining raw materials and preparation process are the same as those in Example 5.

[0095] Comparative Example 5

[0096] Compared with Example 5, the difference in this comparative example is that the flame retardant is different, and the remaining raw materials and preparation process are the same as those in Example 5. The flame retardant in this comparative example is prepared through the following steps:

[0097] Under a nitrogen atmosphere, ethanol and ammonium polyphosphate are mixed and heated to 80°C. Alkali lignin is added, and the temperature is kept constant while stirring continues for 5 hours. After filtration and drying, the flame retardant is obtained. The dosage ratio of ethanol, ammonium polyphosphate, and alkali lignin is 600 mL: 25 g: 12 g.

[0098] Perform performance tests on Example 1, Examples 5 - 8, and Comparative Examples 3 - 5.

[0099] The flame retardant grade is tested according to UL 94, and the thickness of the test specimen is 1.6 mm.

[0100] UV accelerated aging: UV accelerated aging equipment: The wavelength of ultraviolet light is 40 nm, the energy is set at 1.55 W, the blackboard temperature is 50 °C, and accelerated aging is carried out. The tensile strength after 28 days of aging test is measured. The results are shown in Table 2 as follows:

[0101] Table 2

[0102] Project Flame retardant grade Tensile strength / MPa (before aging) Tensile strength / MPa (after aging) Example 1 NR 32.1 28.2 Example 5 V-0 31.5 30.1 Example 6 V-0 32.0 30.6 Example 7 V-0 31.8 20.2 Example 8 V-0 31.6 30.0 Comparative Example 3 V-1 28.6 26.4 Comparative Example 4 V-1 29.2 27.2 Comparative Example 5 V-1 30.4 28.6

[0103] As can be seen from Table 2, there is a good synergistic effect between the self-made flame retardant and the modified fiber of the present invention. Among them: (1) In terms of flame retardant synergy, the nitrogen-silicon composite layer (nitrogen source, silicon source) constructed on the surface of the modified fiber and the phosphorus-nitrogen-boron multi-elements provided by the flame retardant (ammonium polyphosphate as the phosphorus source, lignin / borate as the carbon / boron source) form a complementary flame retardant mechanism, and the flame retardant efficiency is significantly improved through the dual effects of gas phase-condensed phase; (2) In terms of mechanical properties, the interface strengthening phase formed by surface modification of the fiber and the rigid structure of lignin in the flame retardant jointly contribute to the improvement of the mechanical strength of the material; (3) In terms of weather resistance, the dopamine loaded on the modified fiber and the phenolic hydroxyl groups contained in lignin in the flame retardant synergistically play a UV shielding role, effectively delaying the photo-oxidation aging process of the material. Under this system, the stability of the material under long-term exposure to the ultraviolet light environment is significantly enhanced, effectively extending the service life of the material, and providing a strong guarantee for the wide application of the composite material in outdoor applications and other fields.

[0104] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0105] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A biomass-based fiber-modified composite material, characterized in that: The invention comprises the following raw materials by weight: 100 parts of polyolefin resin and 20-50 parts of modified fiber, wherein the modified fiber is obtained by treating wood fiber: the wood fiber is pretreated with dopamine to obtain dopamine pretreated fiber, and then nano-silicon dioxide is deposited on the surface of the dopamine pretreated fiber to obtain the modified fiber.

2. A biomass-based fiber-modified composite material according to claim 1, characterized in that: The modified fiber is prepared by the following steps: The wood fiber is added into a dopamine buffer solution and soaked for 16-24 hours at room temperature, and then taken out, washed with water, and dried to obtain dopamine pretreated fiber; Ethanol, 25% ammonia water and water were mixed to obtain a mixed solution, dopamine pretreated fiber was immersed in the mixed solution, tetraethoxysilane was slowly added, stirred at 50°C for 1-5h, taken out and dried at 80°C to obtain modified fiber.

3. A biomass-based fiber-modified composite material according to claim 2, characterized in that: The concentration of dopamine in the dopamine buffer is 2-3 g / L, the concentration of tris(hydroxymethyl)aminomethane is 1.2 g / L, and the pH value is 8.5; the mass ratio of ethanol, ammonia water, water and tetraethoxysilane is 6.4-6.5:0.6:1:1.4-1.

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4. The biomass-based fiber-modified composite material according to claim 1, characterized in that: The wood fiber is at least one of bamboo fiber, wood powder and palm fiber; the size of the wood fiber is 150-180 μm.

5. The biomass-based fiber-modified composite material according to claim 1, characterized in that: The raw material of the biomass-based fiber-modified composite material also includes 5-15 parts of a flame retardant by weight. The flame retardant is lignin-coated ammonium polyphosphate, and is prepared by adding borate to cross-link and modify the lignin.

6. The biomass-based fiber-modified composite material according to claim 5, characterized in that: The flame retardant is prepared by the following steps: In a nitrogen atmosphere, ethanol and ammonium polyphosphate are mixed, heated to 75-80°C, alkali lignin is added, the temperature is kept constant, stirring is continued for 5-6 hours, and then borate is added, ultrasonically dispersed at room temperature for 50-60 minutes, and a flame retardant is obtained after suction filtration and drying.

7. The biomass-based fiber-modified composite material according to claim 6, characterized in that: The dosage ratio of ethanol, ammonium polyphosphate, alkali lignin and borate is 600mL: 25-30g: 12-15g: 2-6g.

8. The biomass-based fiber-modified composite material according to claim 6, characterized in that: The borate is one of amine borate, zinc borate, aluminum borate and magnesium borate.

9. The biomass-based fiber-modified composite material according to claim 1, characterized in that: The polyolefin resin is one of a polypropylene resin and a polyethylene resin.

10. A method for preparing a biomass-based fiber-modified composite material according to any one of claims 1 to 9, characterized in that: The steps include: The raw materials are mixed to obtain a primary mixture, and then the primary mixture is melt-blended and extruded into granules in a twin-screw extruder, and finally the obtained granules are injection-molded to obtain a biomass-based fiber-modified composite material.

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