A fiber-reinforced high-strength polypropylene composite material and a method for producing the same

Abstract

The present application 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 reinforcing effect of ramie fibers and seaweed fibers and the improvement of the interface by a compatibilizer and a coupling agent exhibits excellent mechanical properties, has high tensile strength, bending strength and impact strength, and can meet the strict requirements of various application scenarios on material strength. The combination of the ramie fibers and the seaweed fibers 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 complex stress conditions.

Description

Technical Field

[0001] This invention belongs to the field of polypropylene composite material technology, and relates to a fiber-reinforced high-strength polypropylene composite material and its preparation method. Background Technology

[0002] With the rapid development of modern industry and the continuous improvement of people's living standards, the performance requirements for polymer materials are becoming increasingly stringent. This is not only reflected in the need for excellent mechanical properties, but also in the requirement that these materials effectively reduce the emission of volatile organic compounds (VOCs) during practical use, thereby minimizing adverse impacts on the environment and human health. Polymer materials are widely used in construction, automobiles, packaging, medical devices, and many other fields. Their performance directly affects product quality and safety, as well as their environmental friendliness. Therefore, developing new materials that meet high-performance requirements while reducing environmental pollution has become a common goal pursued by researchers and enterprises.

[0003] Polypropylene (PP), a common general-purpose plastic, occupies an important position in many industries due to its low density, corrosion resistance, and ease of processing. However, despite its many advantages, PP also faces some challenges, especially when meeting the demands of high-end markets. For example, polypropylene has relatively low mechanical strength and insufficient rigidity, which limits its application in some more demanding fields, such as aerospace and precision instrument manufacturing. Furthermore, PP materials tend to emit high levels of VOCs during production and use, which not only pollutes the environment but may also pose a threat to human health. Therefore, improving the performance of polypropylene and reducing its VOC emissions through modification or innovative technologies has become a key focus of current research.

[0004] Natural fiber materials are widely available, renewable, biodegradable, and possess high strength. Combining them with polypropylene (PP) holds promise for creating composite materials that combine high strength with low emissions. However, current technologies for preparing composite materials by combining fibers with PP still face some challenges, such as poor interfacial compatibility between the fibers and the matrix, and the need for further improvement in the overall performance of the composite materials.

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

[0006] 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 this invention is to address the aforementioned problems in the prior art by proposing a fiber-reinforced high-strength polypropylene composite material with excellent mechanical properties, low VOC emissions, and environmental friendliness.

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

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

[0010] Amino silicone oil is a type of silicone oil containing active amino groups. When it comes into contact with ramie fibers, the amino groups in the amino silicone oil react with the hydroxyl groups on the fiber surface to form stable chemical bonds. This formation of chemical bonds not only further removes impurities and waxes from the fiber surface that are difficult to remove through physical cleaning, but also forms a thin layer of amino silicone oil on the fiber surface. Due to its good hydrophilicity and certain cross-linking ability, amino silicone oil can construct a functional layer on the ramie fiber surface 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 force between the fiber and matrix materials such as resins, thereby greatly improving the surface activity of the fiber. Ramie fibers treated with amino silicone oil, due to their significantly improved surface activity, can form stronger interfacial bonding forces with matrix materials such as resins. This plays an important role in improving the mechanical properties, thermal stability, and durability of composite materials.

[0011] The amount of ramie fiber used in this invention has a significant impact on the mixing uniformity and mechanical properties of the material. Excessive ramie fiber content can easily lead to fiber agglomeration and uneven distribution, increasing processing difficulty, reducing interfacial compatibility, and consequently decreasing the tensile strength, flexural strength, and impact strength of the composite material. Conversely, insufficient ramie fiber content cannot provide adequate reinforcement, resulting in insufficient interfacial bonding and limited improvement in the mechanical properties of the composite material. Therefore, rationally controlling the amount of ramie fiber and optimizing mixing uniformity and interfacial bonding are key to preparing high-performance composite materials in this invention.

[0012] In the aforementioned fiber-reinforced high-strength polypropylene composite material, the seaweed fiber is oxidized with an oxidizing agent.

[0013] In the aforementioned fiber-reinforced high-strength polypropylene composite material, the oxidant is a 2-5 wt% hydrogen peroxide solution. After cleaning and drying the seaweed fibers, oxidation treatment with hydrogen peroxide solution generates more active groups on the fiber surface, thereby enhancing the interfacial bonding between the fiber and the matrix material. Hydrogen peroxide, as a strong oxidant, can generate a large number of active groups such as hydroxyl (-OH), carboxyl (-COOH), and ester (-COO-) groups on the seaweed fiber surface through reactions such as hydroxylation, carboxylation, and esterification. The increase in 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 this invention has a significant impact on the mechanical properties and volatile organic compound (VOC) emission characteristics of the material. Excessive seaweed fiber content can easily lead to fiber agglomeration and uneven distribution, increasing processing difficulty, reducing interfacial compatibility, and consequently decreasing the tensile strength, flexural strength, and impact strength of the composite material. Conversely, insufficient seaweed fiber content cannot provide enough surface-active groups to adsorb and reduce VOCs in the matrix, which is detrimental to improving the low VOC emission performance of the composite material.

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

[0016] In the aforementioned 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 and seaweed fibers to form ester bonds (-COO-). Simultaneously, the anhydride groups can also react with polar groups (such as carbonyl groups and secondary amines) in the PP matrix to form chemical bonds. This formation of chemical bonds not only enhances the interfacial compatibility between the fiber and the matrix but also reduces voids and defects between them, improving the overall uniformity and density of the composite material. The use of tung oil anhydride not only improves the mechanical properties of the composite material but also enhances its processing performance. Due to the enhanced interfacial compatibility, the fiber distribution in the matrix is ​​more uniform, reducing agglomeration and separation during processing. This makes the composite material easier to control during molding, improving production efficiency and product quality.

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

[0018] S1. Prepare the above-mentioned raw materials;

[0019] S2. Mix ramie fiber and seaweed fiber, then add a coupling agent and mix at high temperature;

[0020] S3. Then, polypropylene, compatibilizer and antioxidant are added in sequence and the mixture is then subjected to intensive mixing to obtain a semi-finished product.

[0021] S4. The semi-finished product is crushed and then extruded and granulated using a twin-screw extruder.

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

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

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

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

[0026] 1. The composite material prepared by the present invention through the synergistic reinforcement of ramie fiber and seaweed fiber, as well as the improvement of the interface by compatibilizer and coupling agent, exhibits excellent mechanical properties. It has high tensile strength, flexural strength and impact strength, which 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 maintain good performance under complex stress conditions.

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

[0028] 3. The polypropylene composite material of this invention not only possesses the advantages of high strength and low VOC emissions, but also exhibits good heat resistance, weather resistance, and processability. These enhanced comprehensive properties enable its wide application in multiple fields, including automotive interiors, electronics, and building materials. In the automotive interior sector, this composite material can be used to manufacture dashboards, door panels, and seats, providing a lightweight and environmentally friendly solution. In the electronics sector, its excellent processability and low emission characteristics make it ideal for manufacturing housings and internal components. In the building materials sector, this composite material can be used to produce flooring, wall panels, and decorative materials, improving the environmental friendliness and durability of buildings.

[0029] 4. The ramie fiber and seaweed fiber used in this invention are both natural and renewable resources, widely available and inexpensive. Using 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 reduces dependence on petroleum-based raw materials, lowers production costs, and improves the economics of the materials. Furthermore, the utilization of renewable resources helps alleviate environmental pressure and promotes the development of a green economy. Detailed Implementation

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

[0031] Example 1:

[0032] S1. Prepare the following raw materials in parts by weight: 65 parts polypropylene, 20 parts ramie fiber, 8 parts seaweed fiber, 5 parts compatibilizer, 2 parts coupling agent, and 3 parts 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 fibers, immerse them in a 5wt% amino silicone oil solution for 2 hours, then rinse them with water until neutral, and then dry them.

[0035] S3. After washing and drying the seaweed fiber, oxidize it with 3wt% hydrogen peroxide solution for 1 hour, rinse it with clean water and dry it.

[0036] S4. Add the pretreated ramie fiber and seaweed fiber to a high-speed mixer, then add silane coupling agent, and mix at high speed at 80°C for 30 minutes.

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

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

[0039] Example 2:

[0040] S1. Prepare the following raw materials in parts by weight: 60 parts polypropylene, 15 parts ramie fiber, 5 parts seaweed fiber, 1 part compatibilizer, 1 part coupling agent, and 1 part 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 fibers, immerse them in a 5wt% amino silicone oil solution for 2 hours, then rinse them with water until neutral, and then dry them.

[0043] S3. After washing and drying the seaweed fiber, oxidize it with 3wt% hydrogen peroxide solution for 1 hour, rinse it with clean water and dry it.

[0044] S4. Add the pretreated ramie fiber and seaweed fiber to a high-speed mixer, then add silane coupling agent, and mix at high speed at 80°C for 30 minutes.

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

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

[0047] Example 3:

[0048] S1. Prepare the following raw materials in parts by weight: 70 parts polypropylene, 20 parts ramie fiber, 10 parts seaweed fiber, 5 parts compatibilizer, 5 parts coupling agent, and 5 parts 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 fibers, immerse them in a 5wt% amino silicone oil solution for 2 hours, then rinse them with water until neutral, and then dry them.

[0051] S3. After washing and drying the seaweed fiber, oxidize it with 3wt% hydrogen peroxide solution for 1 hour, rinse it with clean water and dry it.

[0052] S4. Add the pretreated ramie fiber and seaweed fiber to a high-speed mixer, then add silane coupling agent, and mix at high speed at 80°C for 30 minutes.

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

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

[0055] Example 4:

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

[0057] Example 5:

[0058] The only difference from Example 1 is that the seaweed fiber was not oxidized with hydrogen peroxide solution.

[0059] Example 6:

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

[0061] Example 7:

[0062] The only difference from Example 1 is that the mixing process in step S5 was skipped, and the mixed fibers, polypropylene, compatibilizer, and antioxidant were directly fed into a twin-screw extruder for extrusion granulation.

[0063] Example 8:

[0064] The 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 was added to the raw materials.

[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 was 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 no ramie fiber and seaweed fiber were 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 according to the embodiments of the present invention is significantly superior to pure PP material and composite material reinforced with only a single fiber in terms of mechanical properties and VOC emission. This indicates that the synergistic reinforcing effect of ramie fiber and seaweed fiber, as well as the synergistic effect of various additives, effectively improves the overall performance of the composite material.

[0078] The embodiments described herein cover any points not exhaustively within the scope of the technical claims of this invention, as well as new technical solutions formed by equivalent substitutions of one or more technical features in the embodiments. These are all within the scope of the claims of this invention. Furthermore, in all listed or unlisted embodiments of this invention, each parameter in the same embodiment merely represents an instance (i.e., a feasible solution) of its technical solution, and there is no strict coordination or limitation relationship between the parameters. The parameters can be substituted for each other without violating axioms and the claims of this invention, unless otherwise stated.

[0079] The technical means disclosed in this invention are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above descriptions are specific embodiments of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

[0080] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding 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 polypropylene, 15-20 parts ramie fiber, 5-10 parts seaweed fiber, 1-5 parts compatibilizer, 1-5 parts coupling agent, and 1-5 parts antioxidant. Ramie fibers are impregnated with amino silicone oil at a concentration of 3-10 wt% for 1-5 hours; Seaweed fiber is oxidized with an oxidizing agent; The oxidant is a 2-5 wt% hydrogen peroxide solution; The compatibilizer is tung oil anhydride; The preparation method of the composite material includes the following steps: S1. Prepare raw materials; S2. Mix the pretreated ramie fiber and seaweed fiber, and then add a coupling agent for high-temperature mixing; S3. Then, polypropylene, compatibilizer and antioxidant are added in sequence and the mixture is then subjected to intensive mixing to obtain a semi-finished product. S4. The semi-finished product is crushed and then extruded and granulated using a twin-screw extruder.

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

3. The fiber-reinforced high-strength polypropylene composite material according to claim 1, characterized in that, Step S2 involves high-temperature mixing at 70-90℃ for 20-35 minutes.

4. The fiber-reinforced high-strength polypropylene composite material according to claim 1, characterized in that, The mixing temperature in step S3 is 160-180℃, and the time is 15-25 minutes.

5. The fiber-reinforced high-strength polypropylene composite material according to claim 1, characterized in that, The twin-screw extruder operates at a speed of 150-250 r / min, with zone 1 temperatures of 168-172℃, zone 2 temperatures of 175-185℃, zone 3 temperatures of 188-192℃, zone 4 temperatures of 195-205℃, zone 5 temperatures of 208-212℃, and zone 6 temperatures of 195-205℃.

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