Fiber-reinforced high-strength polypropylene composite material and preparation method thereof

Abstract

The invention belongs to the technical field of polypropylene composite materials, and relates to a fiber-reinforced high-strength polypropylene composite material and a preparation method thereof. The composite material prepared through the synergistic enhancement effect of the ramie fibers and the alginate fibers and the improvement of the compatilizer and the coupling agent on an interface shows excellent mechanical properties, has relatively high tensile strength, bending strength and impact strength, can meet the strict requirements of various application scenes on the material strength, and is suitable for industrial production. Wherein the combination of the ramie fiber and the alginate fiber not only enhances the overall strength of the material, but also improves the toughness and fatigue resistance of the material, so that the material can still maintain good performance under the condition of bearing complex stress.

Description

Technical Field

[0001] The invention belongs to the technical field of polypropylene composite materials and relates to a fiber-reinforced high-strength polypropylene composite material and a preparation method thereof. Background Art

[0002] With the rapid development of modern industry and the continuous improvement of people's living standards, the performance requirements for polymer materials are getting higher and higher. This is not only reflected in the need for excellent mechanical properties, but also in the requirement that these materials can effectively reduce the emission of volatile organic compounds (VOC) during actual use, thereby reducing the adverse effects on the environment and human health. Polymer materials are widely used in many fields such as construction, automobiles, packaging, and medical treatment. Their performance is directly related to the quality and safety of the products, as well as their friendliness to the ecological environment. Therefore, developing new materials that meet high-performance requirements and reduce environmental pollution has become a common goal pursued by scientific researchers and enterprises.

[0003] Polypropylene (PP), as a common general-purpose plastic, occupies an important position in many industries due to its low density, corrosion resistance, easy processing and other characteristics. However, despite the many advantages of PP material, it also faces some challenges, especially when facing the needs of the high-end market. For example, the mechanical strength of polypropylene is relatively low and the rigidity is insufficient. These shortcomings limit its application in some fields with more stringent requirements, such as aerospace, precision instrument manufacturing, etc. In addition, PP materials are prone to produce high VOC emissions during production and use, which not only pollutes the environment, but also may pose a threat to human health. In view of this, how to improve the performance of polypropylene and reduce its VOC emissions through modification or innovative technologies has become one of the current research focuses.

[0004] Natural fiber materials have the characteristics of wide sources, renewable, biodegradable and high strength. By combining them with PP, it is expected to prepare a composite material with both high strength and low emission characteristics. However, the current technology of combining fiber with PP to prepare composite materials still has some challenges, such as poor interface compatibility between fiber and matrix, and the comprehensive performance of composite materials needs to be further improved.

[0005] A Chinese patent application document (CN108164820A) discloses a plant fiber / PP composite material. The main research and development goal of the composite material is to improve the mechanical properties, but the emission characteristics of the material, especially the emission of volatile organic compounds (VOCs), are not fully considered during the design and preparation process.

[0006] A Chinese patent application document (CN108164820A) discloses an antibacterial ramie fiber reinforced polypropylene composite material, which improves the antibacterial properties of the composite material by introducing antibacterial components, but does not fully consider the emission characteristics of the material, especially the emission of volatile organic compounds (VOCs). Summary of the invention

[0007] The purpose of the present invention is to address the above problems existing in the prior art and to propose a fiber-reinforced high-strength polypropylene composite material with excellent mechanical properties, low VOC emission and environmental protection.

[0008] The purpose of the present invention can be achieved through the following technical scheme: a fiber-reinforced high-strength polypropylene composite material, the composite material comprises the following raw materials in parts by weight: 60-70 parts of polypropylene, 15-20 parts of ramie fiber, 5-10 parts of seaweed fiber, 1-5 parts of a compatibilizer, 1-5 parts of a coupling agent, and 1-5 parts of an antioxidant.

[0009] In the above-mentioned fiber-reinforced high-strength polypropylene composite material, the ramie fiber is impregnated with amino silicone oil having a concentration of 3-10 wt % for 1-5 hours.

[0010] Amino silicone oil is a silicone oil containing active amino groups. When it comes into contact with ramie fiber, the amino groups in the amino silicone oil can react with the hydroxyl groups on the fiber surface to form a stable chemical bond. The formation of this chemical bond can not only further remove impurities and waxes on the fiber surface that are difficult to remove by physical cleaning, but also form a thin layer of amino silicone oil on the fiber surface. Since amino silicone oil has good hydrophilicity and a certain cross-linking ability, it can build a functional layer on the surface of ramie fiber that is both hydrophilic and has a certain degree of cross-linking. This functional layer not only enhances the polarity of the fiber surface and improves its compatibility with water or other polar substances, but more importantly, it increases the interfacial interaction between the fiber and the matrix material such as resin, thereby greatly improving the surface activity of the fiber. Ramie fiber treated with amino silicone oil can form a stronger interfacial bonding force with the matrix material such as resin due to its significantly improved surface activity, which plays an important role in improving the mechanical properties, thermal stability and durability of composite materials.

[0011] The amount of ramie fiber used in the present invention has a significant effect on the mixing uniformity and mechanical properties of the material. If the amount of ramie fiber used is too much, it is easy to cause fiber agglomeration and uneven distribution, increase processing difficulty, reduce interface compatibility, and thus reduce the tensile strength, bending strength and impact strength of the composite material. On the contrary, if the amount of ramie fiber used is too little, it cannot provide sufficient reinforcement, the interface bonding force is insufficient, and the mechanical properties of the composite material are limited. Therefore, it is the key to prepare high-performance composite materials in the present invention to reasonably control the amount of ramie fiber used and optimize the mixing uniformity and interface bonding force.

[0012] In the above-mentioned fiber-reinforced high-strength polypropylene composite material, the seaweed fiber is oxidized by an oxidant.

[0013] In the above-mentioned fiber-reinforced high-strength polypropylene composite material, the oxidant is a hydrogen peroxide solution with a concentration of 2-5wt%. After the seaweed fiber is cleaned and dried, it is oxidized with a hydrogen peroxide solution, which can generate more active groups on the fiber surface, thereby enhancing the interfacial bonding between the fiber and the matrix material. As a strong oxidant, hydrogen peroxide can generate a large number of active groups such as hydroxyl (-OH), carboxyl (-COOH) and ester (-COO-) on the surface of the seaweed fiber through reactions such as hydroxylation, carboxylation and esterification. The increase of these active groups not only improves the polarity of the fiber surface, but also significantly enhances the compatibility and interfacial bonding between the fiber and the matrix material through chemical bonding, hydrogen bonding and van der Waals forces.

[0014] The amount of seaweed fiber used in the present invention has a significant impact on the mechanical properties and volatile organic compound (VOC) emission characteristics of the material. If the amount of seaweed fiber used is too much, it is easy to cause fiber agglomeration and uneven distribution, increase processing difficulty, reduce interface compatibility, and thus reduce the tensile strength, bending strength and impact strength of the composite material. On the contrary, if the amount of seaweed fiber used is too little, it cannot provide enough surface active groups to adsorb and reduce VOC in the matrix, which is not conducive to improving the low VOC emission performance of the composite material.

[0015] In the above-mentioned fiber-reinforced high-strength polypropylene composite material, the coupling agent includes at least one of a silane coupling agent and a titanate coupling agent.

[0016] In the above-mentioned fiber-reinforced high-strength polypropylene composite material, the compatibilizer is tung oil anhydride. The anhydride groups in tung oil anhydride can react with the hydroxyl groups (-OH) on the surface of ramie fiber and seaweed fiber to generate ester bonds (-COO-). At the same time, the anhydride groups can also react with the polar groups (such as carbonyl, secondary amine, etc.) in the PP matrix to form chemical bonds. The formation of this chemical bond not only enhances the interfacial compatibility between the fiber and the matrix, but also reduces the gaps and defects between the fiber and the matrix, and improves the overall uniformity and compactness of the composite material. The use of oleic anhydride not only improves the mechanical properties of the composite material, but also improves its processing properties. Due to the enhancement of interfacial compatibility, the distribution of the fibers in the matrix is ​​more uniform, reducing the agglomeration and separation phenomena during processing, making the composite material easier to control during the molding process, and improving production efficiency and product quality.

[0017] The present invention also provides a method for preparing the above fiber-reinforced high-strength polypropylene composite material, the method comprising the following steps:

[0018] S1, prepare the above raw materials;

[0019] S2, mixing the ramie fiber and the seaweed fiber, and then adding a coupling agent to mix at high temperature;

[0020] S3, then add polypropylene, compatibilizer and antioxidant in sequence and perform banburying treatment to obtain a semi-finished product;

[0021] S4, the semi-finished product is crushed and then extruded into granules by a twin-screw extruder.

[0022] In the above method for preparing a fiber-reinforced high-strength polypropylene composite material, the high-temperature mixing temperature in step S2 is 70-90° C. and the mixing time is 20-35 min.

[0023] In the above method for preparing a fiber-reinforced high-strength polypropylene composite material, the banburying treatment temperature in step S3 is 160-180° C. and the time is 15-25 min.

[0024] In the above-mentioned method for preparing a fiber-reinforced high-strength polypropylene composite material, the speed of the twin-screw extruder is 150-250r / min, the temperature of zone one is 168-172°C, the temperature of zone two is 175-185°C, the temperature of zone three is 188-192°C, the temperature of zone four is 195-205°C, the temperature of zone five is 208-212°C, and the temperature of zone six is ​​195-205°C.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The composite material prepared by the synergistic reinforcement effect of ramie fiber and seaweed fiber and the improvement of the interface by compatibilizer and coupling agent exhibits excellent mechanical properties, has high tensile strength, flexural strength and impact strength, and can meet the strict requirements of material strength in various application scenarios. The combination of ramie fiber and seaweed fiber not only enhances the overall strength of the material, but also improves its toughness and fatigue resistance, so that it can still maintain good performance under complex stress conditions.

[0027] 2. The present invention utilizes the low volatile organic compound (VOC) characteristics of ramie fiber and seaweed fiber, and further effectively reduces the VOC emission of the composite material during processing and use by optimizing the preparation process. This not only reduces pollution to the environment, but also reduces potential harm to human health, demonstrating good environmental performance.

[0028] 3. The polypropylene composite material of the present invention not only has the advantages of high strength and low VOC emission, but also exhibits good heat resistance, weather resistance and processing performance. The improvement of these comprehensive properties enables it to be widely used in multiple fields, including automotive interiors, electronic appliances and building materials. In the field of automotive interiors, the composite material can be used to make components such as dashboards, door panels and seats, providing lightweight and environmentally friendly solutions; in the field of electronic appliances, its good processing performance and low emission characteristics make it an ideal choice for manufacturing shells and internal components; in the field of building materials, the composite material can be used to produce floors, wall panels and decorative materials, improving the environmental protection and durability of buildings.

[0029] 4. The ramie fiber and seaweed fiber used in the present invention are both natural renewable resources, widely available and inexpensive. The use of these two fibers to reinforce polypropylene (PP) to prepare composite materials not only meets the requirements of sustainable development, but also has broad market prospects. The use of natural fibers not only reduces dependence on petroleum-based raw materials, but also reduces production costs and improves the economic efficiency of materials. In addition, the use of renewable resources helps to reduce environmental pressure and promote the development of a green economy. DETAILED DESCRIPTION

[0030] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0031] Embodiment 1:

[0032] S1. Prepare the following raw materials by weight: 65 parts of polypropylene, 20 parts of ramie fiber, 8 parts of seaweed fiber, 5 parts of compatibilizer, 2 parts of coupling agent, and 3 parts of antioxidant;

[0033] The compatibilizer is tung oil anhydride, the coupling agent is silane coupling agent KH-550, and the antioxidant is antioxidant 1010;

[0034] S2, after washing and drying the ramie fiber, immersing it in a 5wt% amino silicone oil solution for 2h, then rinsing it with clean water until it is neutral, and then drying it;

[0035] S3, after washing and drying the seaweed fiber, oxidizing it with a 3wt% hydrogen peroxide solution for 1h, rinsing it with clean water and drying it;

[0036] S4, adding the pretreated ramie fiber and seaweed fiber into a high-speed mixer, adding a silane coupling agent, and mixing at high speed at 80° C. for 30 min;

[0037] S5. Add the mixed fiber, polypropylene, compatibilizer and antioxidant into a mixer and mix for 20 minutes at a mixing temperature of 175°C.

[0038] S6, and then crushed in a crusher, and then put into a twin-screw extruder for extrusion granulation, wherein the temperatures of zones 1-6 of the extruder are 170°C, 180°C, 190°C, 200°C, 210°C, and 200°C respectively, and the screw speed is 200r / min.

[0039] Embodiment 2:

[0040] S1. Prepare the following raw materials by weight: 60 parts of polypropylene, 15 parts of ramie fiber, 5 parts of seaweed fiber, 1 part of compatibilizer, 1 part of coupling agent, and 1 part of antioxidant;

[0041] The compatibilizer is tung oil anhydride, the coupling agent is silane coupling agent KH-550, and the antioxidant is antioxidant 1010;

[0042] S2, after washing and drying the ramie fiber, immersing it in a 5wt% amino silicone oil solution for 2h, then rinsing it with clean water until it is neutral, and then drying it;

[0043] S3, after washing and drying the seaweed fiber, oxidizing it with a 3wt% hydrogen peroxide solution for 1h, rinsing it with clean water and drying it;

[0044] S4, adding the pretreated ramie fiber and seaweed fiber into a high-speed mixer, adding a silane coupling agent, and mixing at high speed at 80° C. for 30 min;

[0045] S5. Add the mixed fiber, polypropylene, compatibilizer and antioxidant into a mixer and mix for 20 minutes at a mixing temperature of 175°C.

[0046] S6, and then crushed in a crusher, and then put into a twin-screw extruder for extrusion granulation, wherein the temperatures of zones 1-6 of the extruder are 170°C, 180°C, 190°C, 200°C, 210°C, and 200°C respectively, and the screw speed is 200r / min.

[0047] Embodiment 3:

[0048] S1. Prepare the following raw materials by weight: 70 parts of polypropylene, 20 parts of ramie fiber, 10 parts of seaweed fiber, 5 parts of compatibilizer, 5 parts of coupling agent, and 5 parts of antioxidant;

[0049] The compatibilizer is tung oil anhydride, the coupling agent is silane coupling agent KH-550, and the antioxidant is antioxidant 1010;

[0050] S2, after washing and drying the ramie fiber, immersing it in a 5wt% amino silicone oil solution for 2h, then rinsing it with clean water until it is neutral, and then drying it;

[0051] S3, after washing and drying the seaweed fiber, oxidizing it with a 3wt% hydrogen peroxide solution for 1h, rinsing it with clean water and drying it;

[0052] S4, adding the pretreated ramie fiber and seaweed fiber into a high-speed mixer, adding a silane coupling agent, and mixing at high speed at 80° C. for 30 min;

[0053] S5. Add the mixed fiber, polypropylene, compatibilizer and antioxidant into a mixer and mix for 20 minutes at a mixing temperature of 175°C.

[0054] S6, and then crushed in a crusher, and then put into a twin-screw extruder for extrusion granulation, wherein the temperatures of zones 1-6 of the extruder are 170°C, 180°C, 190°C, 200°C, 210°C, and 200°C respectively, and the screw speed is 200r / min.

[0055] Embodiment 4:

[0056] The only difference from Example 1 is that the ramie fiber is not impregnated with amino silicone oil.

[0057] Embodiment 5:

[0058] The only difference from Example 1 is that the seaweed fibers are not oxidized by the hydrogen peroxide solution.

[0059] Embodiment 6:

[0060] The only difference from Example 1 is that in step S4, the pretreated ramie fiber, the pretreated seaweed fiber and the remaining raw materials are directly mixed and kneaded, and finally extrusion granulation is performed.

[0061] Embodiment 7:

[0062] The only difference from Example 1 is that the mixed fibers, polypropylene, compatibilizer and antioxidant are directly put into a twin-screw extruder for extrusion granulation without the banburying treatment in step S5.

[0063] Embodiment 8:

[0064] The only difference from Example 1 is that the ramie fibers that have not been impregnated with amino silicone oil, the seaweed fibers that have not been oxidized with hydrogen peroxide solution, and the remaining raw materials are directly extruded and granulated.

[0065] Comparative Example 1:

[0066] The only difference from Example 1 is that no ramie fiber is added to the raw material.

[0067] Comparative Example 2:

[0068] The only difference from Example 1 is that the amount of ramie fiber added is 40 parts.

[0069] Comparative Example 3:

[0070] The only difference from Example 1 is that no seaweed fiber is added to the raw materials.

[0071] Comparative Example 4:

[0072] The only difference from Example 1 is that the amount of seaweed fiber added is 25 parts.

[0073] Comparative Example 5:

[0074] The only difference from Example 1 is that ramie fiber and seaweed fiber are not added to the raw materials.

[0075] Table 1: Performance test results of polypropylene composite materials prepared in Examples 1-8 and Comparative Examples 1-5

[0076]

[0077] In summary, the composite material prepared in the embodiment of the present invention is significantly superior to the pure PP material and the composite material reinforced with only a single fiber in terms of mechanical properties and VOC emission. This shows that the synergistic reinforcement effect of ramie fiber and seaweed fiber and the synergistic effect of each additive effectively improve the comprehensive performance of the composite material.

[0078] The parts of the embodiments herein that are not exhaustive of the midpoint values ​​of the technical scope claimed for protection by the present invention and the new technical solutions formed by equivalent replacement of single or multiple technical features in the technical solutions of the embodiments are also within the scope claimed for protection by the present invention; at the same time, in all the listed or unlisted embodiments of the scheme of the present invention, each parameter in the same embodiment merely represents an example of its technical solution (i.e., a feasible solution), and there is no strict coordination and limitation relationship between the parameters, wherein the parameters can be replaced with each other without violating the axioms and the claims of the present invention, unless otherwise stated.

[0079] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical schemes composed of any combination of the above technical features. The above is a specific implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

[0080] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A fiber-reinforced high-strength polypropylene composite material, characterized in that: The composite material comprises the following raw materials in parts by weight: 60-70 parts of polypropylene, 15-20 parts of ramie fiber, 5-10 parts of seaweed fiber, 1-5 parts of compatibilizer, 1-5 parts of coupling agent and 1-5 parts of antioxidant.

2. The fiber-reinforced high-strength polypropylene composite material according to claim 1, characterized in that: The ramie fiber is impregnated with 3-10wt% amino silicone oil for 1-5 hours.

3. The fiber-reinforced high-strength polypropylene composite material according to claim 1, characterized in that: The seaweed fiber is oxidized by an oxidant.

4. The fiber-reinforced high-strength polypropylene composite material according to claim 3, characterized in that: The oxidant is a hydrogen peroxide solution with a concentration of 2-5 wt%.

5. The fiber-reinforced high-strength polypropylene composite material according to claim 1, characterized in that: The coupling agent includes at least one of a silane coupling agent and a titanate coupling agent.

6. The fiber-reinforced high-strength polypropylene composite material according to claim 1, characterized in that: The compatibilizer is tung oil anhydride.

7. A method for preparing a fiber-reinforced high-strength polypropylene composite material according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: S1. Prepare the raw materials according to claim 1; S2, mixing the ramie fiber and the seaweed fiber, and then adding a coupling agent to mix at high temperature; S3, then add polypropylene, compatibilizer and antioxidant in sequence and perform banburying treatment to obtain a semi-finished product; S4, the semi-finished product is crushed and then extruded into granules by a twin-screw extruder.

8. The method for preparing a fiber-reinforced high-strength polypropylene composite material according to claim 7, characterized in that: The high temperature mixing temperature of step S2 is 70-90° C. and the mixing time is 20-35 min.

9. The method for preparing a fiber-reinforced high-strength polypropylene composite material according to claim 7, characterized in that: The mixing temperature in step S3 is 160-180° C. and the mixing time is 15-25 min.

10. The method for preparing a fiber-reinforced high-strength polypropylene composite material according to claim 7, characterized in that: The speed of the twin-screw extruder is 150-250r / min, the temperature of zone 1 is 168-172℃, the temperature of zone 2 is 175-185℃, the temperature of zone 3 is 188-192℃, the temperature of zone 4 is 195-205℃, the temperature of zone 5 is 208-212℃, and the temperature of zone 6 is 195-205℃.

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