Low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material, preparation method and application thereof

Abstract

The present application relates to the technical field of bionic composite materials, in particular to a low-temperature impact-resistant self-reinforced polypropylene bionic composite material, a preparation method and application thereof. The low-temperature impact-resistant self-reinforced polypropylene bionic composite material is prepared from n layers of polypropylene woven fabrics, n is greater than or equal to 4, and has a corrugated layered "horn" structure. The polypropylene woven fabric is woven from flat filaments, and the flat filaments have a skin layer, a core layer and a skin structure. The polypropylene bionic composite material of the present application uses polypropylene material for the whole structure, uses the core layer of the polypropylene flat filament as a reinforcing body, and uses the skin layer of the polypropylene flat filament as a matrix to bond each flat filament and each structural layer, so that the whole structure of the composite material can be recycled, the recycling difficulty is significantly reduced, the material recycling rate is effectively improved, and the good interface and interlayer bonding of the self-reinforced polypropylene composite material are realized, and the low-temperature impact resistance is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of biomimetic composite materials technology, and in particular to a low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material, its preparation method, and its application. Background Technology

[0002] Polypropylene (PP) is favored by various industries for its lightweight, high strength, chemical resistance, and good processing properties, and is widely used in packaging materials, automotive parts, building materials, sporting goods, textiles, home appliances, and industrial equipment. However, due to its typically regular molecular structure and weak molecular chain mobility, PP has poor resistance to cracking and impact, especially at low temperatures where it becomes brittle, significantly reducing its impact resistance and greatly limiting its use in cold environments. Furthermore, PP has a relatively low surface hardness compared to other materials, resulting in poor scratch resistance, making it difficult to meet the requirements of components that are prone to wear during use.

[0003] The naturally occurring structure of cow horns provides a valuable reference for improving the performance of composite materials. Cow horns possess a wavy, lamellar structure, with each lamellar composed of tightly packed keratin fibers. These layers and keratin fibers are tightly bonded together through chemical bonds or van der Waals forces, mineral deposition, and the surrounding intercellular matrix. This structure endows cow horns with high strength and toughness, and helps resist friction and wear. Based on the characteristics of the "cow horn" structure, a polypropylene laminated composite material with a wavy, lamellar structure was designed, consisting of multiple layers of bonded polypropylene sheets, to improve the low-temperature impact resistance and scratch resistance of the composite material.

[0004] With increasing global environmental awareness, governments worldwide have introduced policies to promote the recycling of plastic waste. As a widely used plastic material, polypropylene's recycling is particularly important. Self-reinforced composites, also known as monopolymer composites, were first proposed by Capati and Porter of the University of Leeds in 1975. Existing self-reinforced composites include polyethylene, polypropylene, polyethylene terephthalate, polyamide, and polylactic acid. Due to its low cost, polypropylene materials and their products are the main materials in the field of self-reinforced composite material research.

[0005] Self-reinforced polypropylene composite materials that have been successfully commercialized overseas include patented products from British Technology Group International Limited. (CN 1826213A) and patented products of the Dutch company Lankhorst Pure Composites. (CN101326047A). Polypropylene fibers are prepared by direct hot pressing, but the processing temperature range is extremely narrow, which can easily lead to excessive melting of the fibers and loss of their reinforcing effect. The fabric was prepared by hot pressing of co-extruded tape braided fabric with ABA structure. The two layers A are propylene copolymers with a melting point of 135℃. The fabric was prepared by hot pressing at 145℃. However, the bonding strength between the reinforcing fiber and the matrix of this material is poor. Under the action of rapid impact force, delamination occurs, which leads to wrinkles and softening of the material at the corners, and even internal damage.

[0006] China Petroleum & Chemical Corporation (Sinopec) has published two invention patents, CN105563976A and CN107972343A, concerning self-reinforced polypropylene composite materials. The former discloses an outer layer of low-melting-point random copolymer polypropylene, while the latter further specifies the molecular weight of the core and surface polypropylene layers. Both patents use a polymer with... The self-reinforced polypropylene composite material prepared from copolymer polypropylene with a melting point close to that of layer A exhibits similarity to... Similar issues.

[0007] In summary, existing self-reinforced polypropylene composites suffer from technical problems such as poor bonding at the reinforcing fiber-matrix interface, poor bonding between polypropylene layers, and poor impact resistance. The main innovation of this invention lies in solving these technical problems by using novel skin materials and biomimetic methods. Summary of the Invention

[0008] To address the aforementioned issues, this invention provides a low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material, its preparation method, and its application. The entire structure of this biomimetic polypropylene composite material utilizes polypropylene materials, with a core layer of polypropylene flat filaments as reinforcement and a sheath layer of polypropylene flat filaments as the matrix to bond each flat filament and structural layer. This enables full-structure recycling of the composite material, significantly reducing its recycling difficulty, effectively improving the material reuse rate, and achieving excellent interface and interlayer bonding in the self-reinforced polypropylene composite material, as well as a significant improvement in low-temperature impact resistance.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This invention provides a low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material, which is prepared from n layers of polypropylene braided fabric, n≥4, and has a corrugated layered "horn"-like structure;

[0011] The polypropylene woven fabric is obtained by weaving flat filaments, which have a skin layer, a core layer, and a skin layer structure.

[0012] The core layer comprises a mixture of isotactic homopolymer polypropylene and block copolymer polypropylene, a nucleating agent, and a colorant, wherein the mass ratio of the isotactic homopolymer polypropylene to block copolymer polypropylene mixture, the nucleating agent, and the colorant is 90-99:1-5:0-5.

[0013] The isotactic homopolymer polypropylene and block copolymer polypropylene mixture is formed by mixing isotactic homopolymer polypropylene and block copolymer polypropylene in a mass ratio of 8-10:0-2.

[0014] The isotactic homopolymer polypropylene includes isotactic homopolymer polypropylene T30S and / or isotactic homopolymer polypropylene F401.

[0015] The block copolymer polypropylene includes propylene-ethylene block copolymer polypropylene CF330 and / or propylene-ethylene block copolymer polypropylene 700R;

[0016] The skin layer is composed of a mixture of random copolymer polypropylene and propylene-based elastomer, silicone oil lubricant and scratch-resistant agent, and colorant, wherein the mass ratio of the mixture of random copolymer polypropylene and propylene-based elastomer, silicone oil lubricant and scratch-resistant agent, and colorant is 94-99.9:0.1-1:0-5;

[0017] The random copolymer polypropylene and propylene-based elastomer mixture is formed by mixing propylene-ethylene-butene terpolymer and metallocene-catalyzed polypropylene elastomer at a mass ratio of 8-10:0-2.

[0018] The propylene-ethylene-butene terpolymer includes propylene-ethylene-butene terpolymer 1007;

[0019] The metallocene-catalyzed polypropylene elastomer includes metallocene-catalyzed polypropylene elastomers Vistamaxx 6000 or 6102.

[0020] The mass ratio of the core layer to the skin layer is 70-90:10-30, and the skin layers on both sides of the core layer are of equal mass.

[0021] Preferably, the thickness of the polypropylene woven fabric is 0.1–0.2 mm, and the basis weight is 210–270 g / m². 2 .

[0022] Preferably, the width of the flat wire is 1.5 to 2.5 mm, the thickness is 0.04 to 0.06 mm, and the tensile modulus is not less than 10 GPa.

[0023] Preferably, the nucleating agent comprises a β-nucleating agent and polypropylene particles, or calcium carbonate and polypropylene particles;

[0024] The β-nucleating agent includes calcium stearate, and the mass ratio of the β-nucleating agent to polypropylene particles is 5:95.

[0025] The mass ratio of calcium carbonate to polypropylene particles is 5:95;

[0026] The preparation method of the nucleating agent includes: adding the β-nucleating agent or calcium carbonate to polypropylene particles and co-extruding them in a screw extruder at a temperature of 200°C, followed by granulation;

[0027] The colorant comprises pigments and polypropylene particles, wherein the pigments include inorganic pigments and organic pigments;

[0028] The mass ratio of the pigment to the polypropylene particles is 5:95;

[0029] The method for preparing the colorant includes: co-extruding the pigment and polypropylene particles in a screw extruder at a temperature of 200°C, followed by granulation;

[0030] The silicone oil lubricant for scratch resistance comprises polydimethylsiloxane and polypropylene particles, wherein the mass ratio of polydimethylsiloxane to polypropylene particles is 5:95.

[0031] The preparation method of the silicone oil lubricant and scratch-resistant agent includes: co-extruding the polydimethylsiloxane and polypropylene particles in a screw extruder at a temperature of 200°C, followed by granulation;

[0032] The polypropylene particles are grade 1007.

[0033] This invention also provides a method for preparing the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material described in the above technical solution, comprising the following steps:

[0034] 1) According to the skin, core and skin structure of the flat yarn, the components are co-extruded, cooled to form a film, cut into filaments, stretched, heat-set and cooled to obtain flat yarns with a stretch ratio of not less than 10.

[0035] 2) The flat yarns obtained in step 1) are woven into a polypropylene woven fabric with a plain or twill weave structure by interlacing the warp and weft directions;

[0036] 3) Stack the n layers of polypropylene woven fabric obtained in step 2), press them through a composite process, and obtain a low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material.

[0037] Preferably, the co-extrusion temperature in step 1) is 230–250°C;

[0038] The cooling film formation process involves water cooling the extrudate at 25°C to form a three-layer co-extruded film with a thickness of 0.20–0.30 mm and a “skin-core-skin” structure.

[0039] The slicing refers to cutting the three-layer co-extruded film into slivers 2-5 mm wide;

[0040] The stretching conditions include: a temperature of 120–140°C, a traction rate of 4–6 m / min, a stretching rate of 40–70 m / min, and a stretching ratio of more than 10 times.

[0041] The heat setting temperature is 60–70°C;

[0042] The cooling temperature is 20–30°C.

[0043] Preferably, the conditions for the composite process in step 3) include: heating temperature of 130-140°C, speed of 2 m / min, and cooling temperature of 20-50°C.

[0044] The present invention also provides the application of the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material described above in improving the tensile strength of polypropylene composite materials.

[0045] The present invention also provides the application of the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material described above in improving the tensile modulus of polypropylene composite materials.

[0046] The present invention also provides the application of the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material described above in improving the impact strength of polypropylene composite materials.

[0047] The beneficial effects of this invention are:

[0048] This invention draws inspiration from the high-strength, high-toughness, and friction- and wear-resistant horn-shaped structure found in nature, designing and preparing a self-reinforced polypropylene composite material with a corrugated layered structure based on the bonding of multiple layers of polypropylene sheets. The skin layer of this self-reinforced polypropylene composite material uses a mixture of random copolymer polypropylene and propylene-based elastomer, which has a lower melting point than the 135-140℃ copolymer polypropylene used in existing skin materials. This significantly improves the interfacial bonding strength between the reinforcing fibers and the matrix, as well as the interlayer bonding of polypropylene, and solves the problem of wrinkling and softening at the edges of the structural parts during subsequent compression molding. Simultaneously, the improved bonding performance significantly enhances the impact toughness of the polypropylene composite material, especially its low-temperature impact resistance. Furthermore, the invention addresses the poor scratch resistance and easy wear of polypropylene materials by adding a small amount of scratch-resistant agent to the skin layer material. Since the entire structure of the polypropylene composite material of this invention is made of polypropylene, with polypropylene accounting for over 99.2% by mass, other additives serve functions such as coloring, improving crystallization, or scratch resistance, without affecting the reusability of the polypropylene material. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0050] Figure 1 It is a self-reinforced polypropylene composite material (10) with a corrugated layered structure, which is made by pressing polypropylene fabric (20);

[0051] Figure 2 It is a fabric (20) with a twill or plain weave structure woven from polypropylene flat yarns (30) in the warp and weft directions;

[0052] Figure 3 The fabric (20) is in the form of twill weave (21) and plain weave (22), respectively;

[0053] Figure 4 Flat filaments (30) are formed by stretching a polypropylene co-extruded film composed of a "skin-core-skin" structure;

[0054] Figure 5 Here is a photograph of the self-reinforced polypropylene composite material (30) used for performance testing;

[0055] Figure 6 The image shows the physical morphology of the 8-layer composite material after tensile and impact performance tests. Detailed Implementation

[0056] This invention provides a low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material, prepared from n layers of polypropylene braided fabric, where n≥4, and possessing a corrugated layered "horn"-like structure, such as... Figure 1 As shown; the polypropylene woven fabric is obtained by weaving flat yarns, and the woven fabric and its structure are shown in the figures. Figure 2 , Figure 3 The flat filament has a sheath, a core, and a sheath structure, such as... Figure 4As shown; the core layer comprises a mixture of isotactic homopolymer polypropylene and block copolymer polypropylene, a nucleating agent, and a colorant, wherein the mass ratio of the isotactic homopolymer polypropylene to block copolymer polypropylene, the nucleating agent, and the colorant is 90-99:1-5:0-5; the isotactic homopolymer polypropylene to block copolymer polypropylene mixture is formed by mixing isotactic homopolymer polypropylene and block copolymer polypropylene in a mass ratio of 8-10:0-2; the isotactic homopolymer polypropylene includes isotactic homopolymer polypropylene T30S and / or isotactic homopolymer polypropylene F401; the block copolymer polypropylene includes block copolymer polypropylene CF330 and / or block copolymer polypropylene 700R; the skin layer comprises... The product comprises a mixture of random copolymer polypropylene and propylene-based elastomer, silicone oil lubricant and scratch-resistant agent, and colorant. The mass ratio of the random copolymer polypropylene and propylene-based elastomer mixture, silicone oil lubricant and scratch-resistant agent, and colorant is 94–99.9:0.1–1:0–5. The random copolymer polypropylene and propylene-based elastomer mixture is formed by mixing propylene-ethylene-butene terpolymer and metallocene-catalyzed polypropylene elastomer at a mass ratio of 8–10:0–2. The propylene-ethylene-butene terpolymer includes propylene-ethylene-butene terpolymer 1007. The metallocene-catalyzed polypropylene elastomer includes metallocene-catalyzed polypropylene elastomer Vistamaxx 6000 or 6102. The mass ratio of the core layer to the skin layer is 70–90:10–30, and the skin layers on both sides of the core layer are of equal mass.

[0057] In this invention, the isotactic homopolymer polypropylene has a melting point of 160–180°C and an isotactic index of not less than 95%. In this invention, the propylene-ethylene-butene terpolymer has a melting point not higher than 135°C. The polypropylene types described above in this invention are derived from commercially available grades from companies such as Sinopec, Hanwha Group, ExxonMobil, and Dow Chemical.

[0058] In this invention, the thickness of the polypropylene woven fabric is preferably 0.1–0.2 mm, and the basis weight is preferably 210–270 g / m³. 2In this invention, the width of the flat filament is preferably 1.5–2.5 mm, the thickness is preferably 0.04–0.06 mm, and the tensile modulus is preferably not less than 10 GPa. In this invention, the components of the nucleating agent preferably include a β-nucleating agent and polypropylene particles, or calcium carbonate and polypropylene particles; the β-nucleating agent preferably includes calcium stearate, and the mass ratio of the β-nucleating agent to polypropylene particles is preferably 5:95; the mass ratio of calcium carbonate to polypropylene particles is preferably 5:95; the preparation method of the nucleating agent preferably includes: adding the β-nucleating agent or calcium carbonate to polypropylene particles and co-extruding them in a screw extruder at a temperature of 200°C, followed by granulation, wherein the particles are irregular particles with a size between 4-6 mm in any direction, spherical, ellipsoidal, or cylindrical in shape. In this invention, the components of the colorant preferably include pigments and polypropylene particles, and the pigments include inorganic pigments and organic pigments.

[0059] The preferred mass ratio of the pigment to polypropylene particles is 5:95. The preferred method for preparing the colorant includes: co-extruding the pigment and polypropylene particles in a screw extruder at 200°C, followed by granulation, wherein the particles are irregularly shaped particles with a size between 4-6 mm in any direction, forming spherical, ellipsoidal, or cylindrical shapes. This invention does not specifically limit the types of organic and inorganic pigments. In this invention, the components of the silicone oil lubricant and scratch-resistant agent preferably include polydimethylsiloxane and polypropylene particles, with a preferred mass ratio of 5:95. The preferred method for preparing the silicone oil lubricant and scratch-resistant agent includes: co-extruding the polydimethylsiloxane and polypropylene particles in a screw extruder at 200°C, followed by granulation, wherein the particles are irregularly shaped particles with a size between 4-6 mm in any direction, forming spherical, ellipsoidal, or cylindrical shapes. In this invention, the grade of the polypropylene particles is preferably 1007.

[0060] This invention also provides a method for preparing the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material described in the above technical solution, comprising the following steps:

[0061] 1) According to the skin, core and skin structure of the flat yarn, the components are co-extruded, cooled to form a film, cut into filaments, stretched, heat set and cooled to obtain flat yarns with a stretch ratio of not less than 10.

[0062] 2) The flat yarns obtained in step 1) are woven into a polypropylene woven fabric with a plain or twill weave structure by interlacing the warp and weft directions;

[0063] 3) Stack the n layers of polypropylene woven fabric obtained in step 2), press them through a composite process, and obtain a low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material.

[0064] This invention, based on the described flat filament structure (sheath, core, and sheath), obtains flat filaments by co-extrusion, stretching, and cooling of the components, with a stretching ratio of not less than 10. In this invention, the co-extrusion temperature is preferably 230–250°C. In this invention, the cooling film formation involves water cooling the extrudate at 25°C to form a three-layer co-extruded film with a thickness of 0.20–0.30 mm. In this invention, the filament cutting involves cutting the co-extruded film into filaments 2–5 mm wide. In this invention, the stretching temperature is 120–140°C, the traction rate is 4–6 m / min, the stretching rate is 40–70 m / min, and the stretching ratio is greater than 10. In this invention, the heat setting temperature is 60–70°C. In this invention, the cooling temperature is preferably 20–30°C.

[0065] This invention weaves the obtained flat yarns into a polypropylene woven fabric with a plain or twill weave structure using a warp and weft interlacing method. This invention does not impose any particular limitation on the warp and weft weaving method; conventional warp and weft weaving methods can be used.

[0066] This invention involves stacking n layers of polypropylene woven fabric and pressing them through a composite process to obtain a low-temperature impact-resistant, self-reinforcing polypropylene biomimetic composite material. In this invention, the preferred conditions for the composite process include: a heating temperature of 130–140°C, a speed of 2 m / min, and a cooling temperature of 20–50°C. In this invention, the polypropylene woven fabric is preferably pressed in a composite machine.

[0067] The present invention also provides the application of the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material described above in improving the tensile strength of polypropylene composite materials.

[0068] The present invention also provides the application of the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material described above in improving the tensile modulus of polypropylene composite materials.

[0069] The present invention also provides the application of the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material described above in improving the impact strength of polypropylene composite materials.

[0070] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0071] Example 1

[0072] A low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material (10):

[0073] The flat filament (30) is formed by stretching a film 10 times by three-layer co-extrusion of 90 parts by weight of high melting point polypropylene core layer (31) and 10 parts by weight of low melting point polypropylene skin layer (32) in a skin-core-skin ratio of 5:90:5. The core layer (31) is composed of 95 parts by weight of isotactic homopolymer polypropylene T30S and 5 parts by weight of calcium carbonate nucleating agent masterbatch. The skin layer (32) is composed of 99 parts by weight of propylene-ethylene-butene terpolymer 1007 and metallocene catalyzed polypropylene elastomer Vistamaxx 6000 in a mass ratio of 8:2 and 1 part by weight of polydimethylsiloxane silicone oil lubricant and scratch resistant agent.

[0074] The calcium carbonate nucleating agent masterbatch consists of calcium carbonate and polypropylene particles in a mass ratio of 5:95. The calcium carbonate and polypropylene particles are co-extruded in a screw at 200°C and then granulated. The particles are irregular spherical, ellipsoidal, or cylindrical particles with a size between 4-6 mm in any direction. The polypropylene particles are grade 1007.

[0075] The components of the polydimethylsiloxane silicone oil lubricant and scratch-resistant agent are polydimethylsiloxane and polypropylene particles in a mass ratio of 5:95. The polydimethylsiloxane and polypropylene particles are co-extruded in a screw at 200°C and then granulated. The particles are irregular granules with a size between 4-6 mm in any direction, in the shape of spheres, ellipsoids or cylinders. The polypropylene particles are grade 1007.

[0076] Preparation method of flat filaments: A three-layer co-extruded film with a "skin-core-skin" structure was prepared using core layer (31) and skin layer (32) materials. The co-extrusion temperature was 240℃, and the film was water-cooled at 25℃ to a thickness of 0.20mm. The co-extruded film was cut into filaments with a width of 4mm, stretched at a stretching temperature of 130℃, a traction rate of 5.4m / min, and a stretching rate of 55m / min, and then heat-set at 70℃. Flat filaments (30) were obtained by cooling at 25℃. The stretching ratio was 10 times, the width of the flat filaments was 1.5~2.5mm with an average of 2.0mm, and the thickness was 0.04~0.06mm with an average of 0.05mm.

[0077] Examples 2-4 were prepared by using different stretching ratios and "skin-core-skin" ratios based on Example 1. Example 5 was prepared by using calcium stearate nucleating agent masterbatch based on Example 1. Example 6 was prepared by using carbon black colorant based on Example 1. Examples 7-10 were prepared by using different high-melting-point polypropylene core layer (31) and low-melting-point polypropylene skin layer (32) materials to prepare flat yarns (30). The specific formulations are shown in Table 1.

[0078] The calcium stearate nucleating agent masterbatch consists of calcium stearate and polypropylene particles in a mass ratio of 5:95. The calcium stearate and polypropylene particles are co-extruded in a screw extruder at 200°C and then granulated. The particles are irregular spherical, ellipsoidal, or cylindrical particles with a size between 4-6 mm in any direction. The grade of the polypropylene particles is 1007.

[0079] The carbon black colorant consists of carbon black and polypropylene particles in a mass ratio of 5:95. The carbon black and polypropylene particles are co-extruded in a screw extruder at 200°C and then granulated. The particles are irregular granules with a size between 4-6 mm in any direction, in the shape of spheres, ellipsoids, or cylinders. The grade of the polypropylene particles is 1007.

[0080] Table 1 Material formulation of low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material

[0081]

[0082]

[0083] Example 11

[0084] Fabrics (20) with twill weave (21) or plain weave (22) are formed by weaving the flat yarns (30) obtained according to Examples 1-10 above through warp and weft directions, such as Figure 3 As shown. Multiple layers of polypropylene woven fabric (20) are stacked sequentially and molded using a composite process to create a biomimetic composite material (10) with a "horn-like" structure, as shown. Figure 1 As shown.

[0085] The fabric (20) woven from flat yarns obtained in Example 1 was stacked in the same warp and weft directions in four layers, and then pressed into a biomimetic composite material (10) through a composite machine process of preheating, heating, and cooling. Figure 5 As shown. The settings for the laminating machine are: heating temperature 135℃, roller speed 2.0m / min, and cooling temperature 20℃.

[0086] Example 12

[0087] The biomimetic composite material (10) was prepared by thermally bonding eight layers of fabric (20) according to the method of Example 11.

[0088] Example 13

[0089] The biomimetic composite material (10) was prepared by thermally bonding 10 layers of fabric (20) according to the method of Example 11.

[0090] Example 14

[0091] The 12-layer fabric (20) was thermally bonded to prepare the biomimetic composite material (10) according to the method of Example 11.

[0092] Comparative Example 1

[0093] The flat yarn (30) is made by stretching a film formed by three co-extrusions of 90 parts by weight of high melting point polypropylene core layer (31) and 10 parts by weight of low melting point polypropylene skin layer (32) in a skin-core-skin ratio of 5:90:5. The core layer (31) is isotactic homopolymer polypropylene T30S and the skin layer (32) is propylene-ethylene-butene terpolymer 1007.

[0094] The preparation methods for flat yarns and fabrics are the same as in Example 1.

[0095] Eight layers of fabric (20) are stacked in the same warp and weft direction and pressed into a biomimetic composite material (10) through a composite machine preheating, heating and cooling process. The composite machine is set with heating temperature of 135℃, roller speed of 2.0m / min and cooling temperature of 20℃.

[0096] The tensile strength / modulus, room temperature / low temperature unnotched impact resistance, and interlaminar peel force of the composite material (10) were tested according to ISO 527-2 "Plastics - Tensile properties test method", ISO 179-1 "Plastics - Determination of impact strength of simply supported beams", and GB 8808-88 "Peel test method for flexible composite plastic materials". The test results of the physical and mechanical properties of the biomimetic composite materials prepared in Examples 11-14 and Comparative Example 1 are shown in Table 2.

[0097] Images of specimens from Example 12 after tensile, simply supported beam impact, and drop hammer impact tests are shown below. Figure 6 .

[0098] Table 2. Performance test results of biomimetic composite materials

[0099]

[0100] The test results of Examples 11-14 show that the present invention prepares a fully structural polypropylene composite material with good mechanical properties. Compared with the comparative example, the tensile strength, modulus, impact strength, and interlaminar peel force of Examples 11-14 are significantly improved. This is mainly because the skin layer of the composite material in Examples 11-14 uses a mixture of low-melting-point (100-130℃) random copolymer polypropylene and propylene-based elastomer, which has a lower melting point than the 130-140℃ random copolymer polypropylene used in the skin layer of the comparative example. This significantly improves the interfacial bonding strength between the reinforcing fiber and the matrix, as well as the interlaminar bonding of the polypropylene layers, and solves the problem of wrinkling and softening at the corners of the structural parts during subsequent compression molding. At the same time, due to the improved bonding performance, the impact toughness of the polypropylene composite material is significantly improved, especially its low-temperature impact resistance. In addition, in the composite material prepared by the present invention using isotactic polypropylene core material, random copolymer polypropylene and metallocene polypropylene skin material, nucleating agent / coloring agent polypropylene masterbatch, and a small amount of anti-scratch agent, the proportion of polypropylene is more than 99.2%, which can effectively realize the recycling and reuse of the entire structural material.

[0101] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material, characterized in that, It is prepared from n layers of polypropylene woven fabric, n≥4, and has a corrugated layered "horn-like" structure; The polypropylene woven fabric is obtained by weaving flat filaments, which have a skin layer, a core layer, and a skin layer structure. The core layer comprises a mixture of isotactic homopolymer polypropylene and block copolymer polypropylene, a nucleating agent, and a colorant, wherein the mass ratio of the isotactic homopolymer polypropylene to block copolymer polypropylene mixture, the nucleating agent, and the colorant is 90-99:1-5:0-5. The isotactic homopolymer polypropylene and block copolymer polypropylene mixture is formed by mixing isotactic homopolymer polypropylene and block copolymer polypropylene in a mass ratio of 8-10:0-2; The isotactic homopolymer polypropylene includes isotactic homopolymer polypropylene T30S and / or isotactic homopolymer polypropylene F401. The block copolymer polypropylene includes propylene-ethylene block copolymer polypropylene CF330 and / or propylene-ethylene block copolymer polypropylene 700R; The skin layer is composed of a mixture of random copolymer polypropylene and propylene-based elastomer, silicone oil lubricant and scratch-resistant agent, and colorant, wherein the mass ratio of the mixture of random copolymer polypropylene and propylene-based elastomer, silicone oil lubricant and scratch-resistant agent, and colorant is 94-99.9:0.1-1:0-5; The random copolymer polypropylene and propylene-based elastomer mixture is formed by mixing propylene-ethylene-butene terpolymer and metallocene-catalyzed polypropylene elastomer at a mass ratio of 8-10:0-2. The propylene-ethylene-butene terpolymer includes propylene-ethylene-butene terpolymer 1007; The metallocene-catalyzed polypropylene elastomer includes metallocene-catalyzed polypropylene elastomers Vistamaxx 6000 or 6102. The mass ratio of the core layer to the skin layer is 70-90:10-30, and the skin layers on both sides of the core layer are of equal mass.

2. The low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material according to claim 1, characterized in that, The polypropylene woven fabric has a thickness of 0.1–0.2 mm and a basis weight of 210–270 g / m³. 2 .

3. The low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material according to claim 1, characterized in that, The flat wire has a width of 1.5–2.5 mm, a thickness of 0.04–0.06 mm, and a tensile modulus of not less than 10 GPa.

4. The low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material according to claim 1, characterized in that, The nucleating agent comprises a β-nucleating agent and polypropylene particles, or calcium carbonate and polypropylene particles. The β-nucleating agent includes calcium stearate, and the mass ratio of the β-nucleating agent to polypropylene particles is 5:

95. The mass ratio of calcium carbonate to polypropylene particles is 5:95; The preparation method of the nucleating agent includes: co-extruding the β-nucleating agent or calcium carbonate with polypropylene particles in a screw extruder at a temperature of 200°C, followed by granulation; The colorant comprises pigments and polypropylene particles, wherein the pigments include inorganic pigments and organic pigments; The mass ratio of the pigment to the polypropylene particles is 5:95; The method for preparing the colorant includes: co-extruding the pigment and polypropylene particles in a screw extruder at a temperature of 200°C, followed by granulation; The components of the silicone oil lubricant and scratch-resistant agent include polydimethylsiloxane and polypropylene particles, wherein the mass ratio of polydimethylsiloxane to polypropylene particles is 5:

95. The preparation method of the silicone oil lubricant and scratch-resistant agent includes: co-extruding the polydimethylsiloxane and polypropylene particles in a screw extruder at a temperature of 200°C, followed by granulation.

5. A method for preparing the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material according to any one of claims 1 to 4, characterized in that, Includes the following steps: 1) According to the skin, core and skin structure of the flat yarn, the components are co-extruded, cooled to form a film, cut into filaments, stretched, heat-set and cooled to obtain flat yarns with a stretch ratio of not less than 10. 2) The flat yarns obtained in step 1) are woven into a polypropylene woven fabric with a plain or twill weave structure by interlacing the warp and weft directions; 3) Stack n layers of the polypropylene woven fabric obtained in step 2), press them through a composite process, and obtain a low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material. The co-extrusion temperature in step 1) is 230–250°C; the cooling and film formation involves water cooling the extrudate at 25°C to form a 0.20–0.30 mm thick three-layer co-extruded film with a "skin-core-skin" structure; the shaving involves cutting the three-layer co-extruded film into 2–5 mm wide filaments; the stretching conditions include: temperature 120–140°C, traction rate 4–6 m / min, stretching rate 40–70 m / min, and stretch ratio of 10 times or more; the heat setting temperature is 60–70°C; and the cooling temperature is 20–30°C. The conditions for the composite process in step 3) include: heating temperature of 130-140℃, speed of 2m / min, and cooling temperature of 20-50℃.

6. The application of the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material according to any one of claims 1 to 4 in improving the tensile strength of polypropylene composite materials.

7. The application of the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material according to any one of claims 1 to 4 in improving the tensile modulus of polypropylene composite materials.

8. The application of the low-temperature impact-resistant self-reinforced polypropylene biomimetic composite material according to any one of claims 1 to 4 in improving the impact strength of polypropylene composite materials.

Images