A method for producing a needle-like plant fiber-reinforced polyamide composite

Abstract

The present application relates to the technical field of wood plastic composite, and discloses a preparation method of acicular plant fiber reinforced polyamide composite material.The method comprises the following steps: 1, selecting economic biomass material, and preliminarily separating the material through hydrothermal treatment; 2, further separating and processing the biomass material after the hydrothermal treatment into acicular plant fiber through rubbing and rolling type plant fiber pulverizer; 3, preparing a mixed material; 4, preparing acicular plant fiber reinforced polyamide composite material master batch; and 5, processing and forming.The different diameters and aspect ratios of plant fibers will affect the mechanical properties of wood plastic composite material.The present application discloses a simple preparation method of high-aspect-ratio plant fiber, and a method for preparing high-strength wood plastic composite material by using the high-aspect-ratio plant fiber to reinforce polyamide plastic.The composite material prepared by the present application has stable high-strength bending strength, bending modulus, tensile strength and tensile modulus, and has important application value in the technical field of wood plastic composite material.

Description

Technical Field

[0001] This invention relates to a polyamide-based composite material and its preparation method. Background Technology

[0002] Wood-plastic composites combine biomass fibers (such as wood chips, rice husks, and other agricultural and forestry waste) with thermoplastic plastics (such as PE, PP, PA, etc.), achieving high-value-added recycling of resources, which not only alleviates the pressure on timber supply but also reduces plastic pollution.

[0003] Existing wood-plastic composites mostly use general-purpose plastics with low strength (such as PE, PP, PVC, etc.) as the matrix, resulting in insufficient mechanical strength and weather resistance. Polyamide wood-plastic composites prepared at high temperatures using engineering plastic polyamide as the matrix exhibit high strength and toughness; however, current technologies generally use powdered or granular biomass fragments as the matrix. This results in a loss of a large aspect ratio, and the reinforcing effect of biomass fibers is limited. Furthermore, pure fibers are too flexible and easily entangle and clump together during composite material preparation, causing difficulties in feeding and uneven dispersion in the molten matrix. Therefore, preparing needle-like fibers that are both heat-resistant and have a large aspect ratio with good flowability is a technical problem that needs to be solved in this field. Summary of the Invention

[0004] This invention aims to address the problems of limited reinforcement, stress concentration, difficulty in effectively transferring and dispersing loads, and limitations on the optimization of specific directional properties of commonly used powdered plant fibers in polyamide wood-plastic composites. Therefore, it provides a needle-like plant fiber reinforced polyamide composite material and its preparation method.

[0005] A needle-like plant fiber reinforced polyamide composite material is prepared from hydrothermally treated needle-like plant fibers and polyamide plastic; the mass percentage of hydrothermally treated plant fibers in the plant fiber reinforced polyamide composite material is 1%-90%. The hydrothermally treated plant fibers are obtained from biomass materials such as wood or bamboo through specific treatment, and the length of the treated plant fibers is 2-4 mm, with an aspect ratio of 5-15.

[0006] A method for preparing a needle-like plant fiber reinforced polyamide composite material, comprising the following steps:

[0007] 1. Immerse block or sheet biomass raw materials in water at a solid-liquid ratio of 1:(5-10), and hydrolyze them for 60-100 minutes at a reaction temperature of 150℃-190℃. Then dry them to obtain pre-hydrolyzed biomass materials.

[0008] 2. The pre-hydrolyzed biomass material obtained in step 1 is crushed and processed by a kneading and rolling plant fiber crusher to screen out plant fibers with a length of 2-4 mm and an aspect ratio of 5-15. The fibers are then placed in a drying oven and dried at (103±2)℃ until the moisture content is less than 3%.

[0009] 3. The polyamide plastic and the plant fiber obtained in step 2 are placed in a high-speed mixer and mixed evenly to obtain a mixture; the mass percentage of plant fiber in the mixture is 1% to 90%;

[0010] IV. The mixture obtained in step 3 is melt-mixed and granulated to obtain needle-shaped plant fiber reinforced polyamide composite material masterbatch;

[0011] 5. The masterbatch obtained in step 4 is processed and shaped to obtain needle-shaped plant fiber reinforced polyamide composite material.

[0012] The beneficial effects of this invention are:

[0013] 1. In hydrothermal treated biomass raw materials, hemicellulose and some lignin in the cell walls are degraded and removed. These components are mainly located in the middle lamella and between cellulose filaments. Their removal weakens the inter-fiber forces, providing favorable conditions for fiber separation. This invention first pulverizes the hydrothermally treated block or sheet-like plant fibers through a kneading process, easily obtaining needle-like fibers with a high aspect ratio and excellent flowability. During the granulation step, the fibers are further separated into finer fibers with an even higher aspect ratio through the high shear force of the equipment. These fibers play a crucial reinforcing role in the matrix.

[0014] 2. During the processing and molding, the plant fibers undergo a third separation under the shear force of the twin-screw extruder, resulting in more uniform and stable dimensions. This helps improve the quality stability of the composite material, ensuring product consistency and reliability. With appropriate die flow channel design, the plant fibers align in the same direction, and their length direction tends to be parallel to the extrusion direction. This orientation further enhances the composite material's properties in specific directions, enabling it to meet the special performance requirements of different application scenarios.

[0015] 3. Needle-shaped plant fibers with a high aspect ratio can form a continuous three-dimensional network structure in the polyamide matrix, which significantly improves the bending strength, bending modulus, tensile strength and tensile modulus of wood-plastic composites. This enables the material to effectively resist deformation and failure when subjected to external forces, meeting the requirements of various engineering applications for material strength and stiffness.

[0016] 4. The slender shape of needle-like plant fibers allows them to optimize stress transfer efficiency within the matrix. The interweaving and orientation of the fibers can evenly distribute external loads, preventing stress concentration and thus enhancing the overall performance of the material.

[0017] 5. The bridging effect of fibers can inhibit crack propagation and improve the toughness and impact resistance of materials. When subjected to impact, needle-like plant fibers can prevent further crack propagation, giving composite materials better impact resistance and improving the reliability and safety of the material. Detailed Implementation

[0018] Specific Implementation Method 1: This implementation method discloses a needle-like plant fiber reinforced polyamide composite material, which is prepared from pre-hydrolyzed needle-like plant fibers and polyamide plastic; the mass percentage of the treated plant fibers in the plant fiber reinforced polyamide composite material is 1%-90%. The pre-hydrolyzed plant fibers are obtained from biomass materials (such as wood or bamboo) through specific treatment, and the length of the treated plant fibers is 2-4 mm, with an aspect ratio of 5-15.

[0019] The beneficial effects of this embodiment are:

[0020] 1. In hydrothermal treated biomass raw materials, hemicellulose and some lignin in the cell walls are degraded and removed. These components are mainly located in the middle lamella and between cellulose filaments. Their removal weakens the inter-fiber forces, providing favorable conditions for fiber separation. This invention first pulverizes the hydrothermally treated block or sheet-like plant fibers through a kneading process, easily obtaining needle-like fibers with a high aspect ratio and excellent flowability. During the granulation step, the fibers are further separated into finer fibers with an even higher aspect ratio through the high shear force of the equipment. These fibers play a crucial reinforcing role in the matrix.

[0021] 2. During the processing and molding, the plant fibers undergo a third separation under the shear force of the twin-screw extruder, resulting in more uniform and stable dimensions. This helps improve the quality stability of the composite material, ensuring product consistency and reliability. With appropriate die flow channel design, the plant fibers align in the same direction, and their length direction tends to be parallel to the extrusion direction. This orientation further enhances the composite material's properties in specific directions, enabling it to meet the special performance requirements of different application scenarios.

[0022] 3. Needle-shaped plant fibers with a high aspect ratio can form a continuous three-dimensional network structure in the polyamide matrix, which significantly improves the bending strength, bending modulus, tensile strength and tensile modulus of wood-plastic composites. This enables the material to effectively resist deformation and failure when subjected to external forces, meeting the requirements of various engineering applications for material strength and stiffness.

[0023] 4. The slender shape of needle-like plant fibers allows them to optimize stress transfer efficiency within the matrix. The interweaving and orientation of the fibers can evenly distribute external loads, preventing stress concentration and thus enhancing the overall performance of the material.

[0024] 5. The bridging effect of fibers can inhibit crack propagation and improve the toughness and impact resistance of materials. When subjected to impact, needle-like plant fibers can prevent further crack propagation, giving composite materials better impact resistance and improving the reliability and safety of the material.

[0025] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the pre-hydrolyzed plant fiber is prepared according to the following steps: The plant fiber is immersed in water at a solid-liquid ratio of 1:(5-10), and the hydrolysis reaction is carried out for 60-100 minutes at a reaction temperature of 150℃-190℃. Then, it is dried to obtain the pre-hydrolyzed plant fiber. Everything else is the same as in Specific Implementation Method One.

[0026] Specific Implementation Method 3: This implementation method provides a method for preparing a needle-like plant fiber reinforced polyamide composite material, characterized by the following steps:

[0027] 1. Immerse block or sheet biomass material in water at a solid-liquid ratio of 1:(5-10), and hydrolyze it for 60-100 minutes at a reaction temperature of 150℃-190℃. Then dry it to obtain pre-hydrolyzed biomass material.

[0028] 2. The pre-hydrolyzed biomass material obtained in step 1 is crushed and processed by a kneading and rolling plant fiber crusher to screen out plant fibers with a length of 2-4 mm and an aspect ratio of 5-15. The fibers are then placed in a drying oven and dried at (103±2)℃ until the moisture content is less than 3%.

[0029] 3. The polyamide plastic and the plant fiber obtained in step 2 are placed in a high-speed mixer and mixed evenly to obtain a mixture; the mass percentage of plant fiber in the mixture is 1% to 90%;

[0030] IV. The mixture obtained in step 3 is melt-mixed and granulated to obtain needle-shaped plant fiber reinforced polyamide composite material masterbatch;

[0031] 5. The masterbatch obtained in step 4 is processed and shaped to obtain needle-shaped plant fiber reinforced polyamide composite material.

[0032] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Three in that the plant fiber mentioned in step one is wood shavings or bamboo strips. Everything else is the same as in Specific Implementation Method Three.

[0033] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Three or Four in that the polyamide plastic mentioned in step three is polyamide 6, polyamide 11, polyamide 12, or polyamide 66n. Everything else is the same as in Specific Implementation Method Three or Four.

[0034] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods Three to Five in that, in step three, the polyamide plastic and pre-hydrolyzed plant fibers are placed in a high-speed mixer and mixed for 7 to 10 minutes at a speed of 500 rpm to 1500 rpm. Everything else is the same as in Specific Implementation Methods Three to Five.

[0035] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods Three to Six in that, in step five, the plant fiber reinforced polyamide composite material masterbatch is processed and shaped at a processing temperature of 220℃~290℃. Everything else is the same as in Specific Implementation Methods Three to Six.

Claims

1. A method for preparing a needle-like plant fiber reinforced polyamide composite material, characterized in that... It is done in the following steps:

1. Immerse block or sheet biomass material in water at a solid-liquid ratio of 1:(5~10), and hydrolyze it for 60min~100min at a reaction temperature of 150℃~190℃. Then dry it to obtain pre-hydrolyzed biomass material.

2. The pre-hydrolyzed biomass material obtained in step one is pulverized using a kneading and rolling plant fiber pulverizer to screen out plant fibers with a length of 2-4 mm and an aspect ratio of 5-15. The fibers are then placed in a drying oven and dried at (103 ± 2) ℃ until the moisture content is below 3%.

3. Place the polyamide plastic and the plant fiber obtained in step 2 into a high-speed mixer and mix them evenly to obtain a mixture; the mass percentage of plant fiber in the mixture is 1% to 90%. IV. The mixture obtained in step 3 is melt-mixed and granulated to obtain needle-shaped plant fiber reinforced polyamide composite material masterbatch; 5. The masterbatch obtained in step 4 is processed and shaped to obtain needle-shaped plant fiber reinforced polyamide composite material.

2. The method for preparing a needle-like plant fiber reinforced polyamide composite material according to claim 1, characterized in that... The biomass material mentioned in step one is wood or bamboo.

3. The method for preparing a needle-like plant fiber reinforced polyamide composite material according to claim 1, characterized in that... The polyamide plastic mentioned in step three is polyamide 6, polyamide 11, polyamide 12 or polyamide 66.

4. The method for preparing a needle-like plant fiber reinforced polyamide composite material according to claim 1, characterized in that... In step three, the polyamide plastic and plant fiber are placed in a high-speed mixer and mixed for 7 to 10 minutes at a speed of 500 rpm to 1500 rpm.

5. The method for preparing a needle-like plant fiber reinforced polyamide composite material according to claim 1, characterized in that, Alternatively, step four can be omitted, and the process can proceed directly to step five for molding. The molding process described in step five is injection molding, extrusion molding, or compression molding.

6. The method for preparing a needle-like plant fiber reinforced polyamide composite material according to claim 1, characterized in that... In step five, the forming process is carried out at a processing temperature of 220℃~290℃.