High-strength high-modulus fiber-reinforced thermoplastic composite material particle and preparation method thereof

Abstract

The invention discloses a high-strength high-modulus fiber-reinforced thermoplastic composite material particle and a preparation method, the particle comprises the following raw materials by weight: 40-70% of a resin matrix mixture and 30-60% of chopped fibers, and the preparation method comprises the following specific steps: step 1, preparing a resin matrix mixture; the preparation method comprises the following steps: adding matrix resin, an antioxidant, a lubricant, a compatilizer and the like into a high-speed mixer according to a certain proportion, and premixing to obtain a resin mixture; 2, feeding the resin mixture from a main feeding port of a double-screw extruder, and then adding a certain proportion of chopped fibers from a side feeding port; and step 3, granulating the compound melt discharged from the die head of the extruder to obtain composite material particles. According to the invention, the preparation of the high-modulus chopped fiber reinforced thermoplastic composite material can be realized, the process is simple, the cost is low, the particles can be subsequently prepared into injection molded parts in various shapes by using an injection molding machine, the problem of low processing efficiency of metal materials is effectively solved, and the method has a wide application prospect in the fields of automobiles and aerospace.

Description

Technical Field

[0001] The present invention relates to the field of composite materials, and particularly to a high-strength and high-modulus fiber-reinforced thermoplastic composite material particle and a preparation method thereof. Background Art

[0002] At present, fiber-reinforced composite materials have been widely used in the fields of sports equipment, automobiles, aerospace, rail transit, etc. due to their advantages such as light weight, high strength, corrosion resistance, and strong designability. In the preparation of composite material products, the injection molding process is widely used due to its advantages such as good formability, fast production speed, recyclability, and adaptability to the rapid molding of complex structural parts. However, the plastic particles currently used for injection molding are limited by the content and length of the chopped fibers. The chopped fiber-reinforced thermoplastic composite materials formed have lower tensile strength and tensile modulus compared to aluminum alloys. The currently disclosed tensile strength range of aluminum alloys is 350 - 450 MPa, and the tensile modulus range is 70 - 90 MPa. The tensile strength and tensile modulus profiles of the composite materials prepared from several common chopped fiber thermoplastic plastic particles at home and abroad are shown in Table 1 and Table 2, which are quite different from the properties of aluminum alloys, thus limiting the application range of the injection molding process.

[0003] Table 1

[0004] Table 2 Summary of the Invention

[0005] The present invention aims to overcome the deficiencies existing in the prior art. The purpose is to provide a high-strength and high-modulus fiber-reinforced thermoplastic composite material particle and a preparation method thereof. On the one hand, through formula improvement, the content of chopped fibers in the plastic particles is increased. On the other hand, through process improvement, the chopped fibers can maintain a better length during the granulation process, and finally the tensile strength and tensile modulus of the composite material made from such particles are greatly improved.

[0006] In the first aspect, the present invention provides a high-strength and high-modulus fiber-reinforced thermoplastic composite material particle, which includes, by weight percentage of raw materials: Chopped fibers, 30 - 60%; Matrix resin, 40 - 70%; Antioxidant 0 - 1%; Lubricant 0 - 1%; Compatibilizer 0 - 5%.

[0007] Further, the average length of the chopped fibers in the high-strength and high-modulus chopped fiber-reinforced thermoplastic composite material particle is 200 - 500 μm.

[0008] Further, the matrix resin is any one or a mixture of several of polyolefin, polyamide (semi-aromatic), polyester, high-temperature nylon, liquid crystal polymer, polyphenylene sulfide, and polyether ether ketone.

[0009] Further, the antioxidant is one or a mixture of several of 2,6-di-tert-butyl-p-cresol, 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tris(ethylene glycol) bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoyl]hexanediamine, tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, pentaerythritol diphosphite dioctadecyl ester, distearyl thiodipropionate; distearyl thiodipropionate, etc.

[0010] Further, the lubricant is one or a mixture of several of polyethylene wax, silicone oil, silicone rubber, erucamide, pentaerythritol stearate, aluminum distearate, calcium stearate, magnesium stearate, zinc stearate, silicone powder, sodium stearate, stearamide, stearic acid, paraffin wax, etc.

[0011] Further, the compatibilizer is one or a mixture of several of maleic anhydride grafted PP, maleic anhydride grafted PE, maleic anhydride grafted PA6, maleic anhydride grafted POE, maleic anhydride grafted AS, maleic anhydride grafted PPO, glycidyl methacrylate grafted ethylene-propylene copolymer, glycidyl methacrylate grafted POE, glycidyl methacrylate grafted ethylene copolymer, glycidyl methacrylate grafted ethylene-acrylate copolymer, etc.

[0012] Further, the chopped fibers are any one or several of carbon fibers, glass fibers, stainless steel fibers, and basalt fibers.

[0013] In a second aspect, the present invention also provides a preparation method of the high-strength and high-modulus fiber-reinforced thermoplastic composite particles based on the above, comprising the following steps: Step 1, adding the matrix resin, antioxidant, lubricant, and compatibilizer into a high-speed mixer according to the weight percentage of the raw materials for premixing to form a resin mixture; Step 2, feeding the premixed resin mixture into the main feeding port of a twin-screw extruder, and feeding the chopped fibers into the side feeding port of the twin-screw extruder according to the weight parts of the raw materials; Step 3, extruding and pelletizing.

[0014] Further, the screw combination of the twin-screw extruder in the second step is two co-rotating and meshing screws, and the ratio of the length to the diameter of the screw, i.e., the ratio of the screw length to the screw diameter, is 30:1 - 50:1.

[0015] Further, the screw includes a first mixing zone and a second mixing zone. The first mixing zone includes two conveying sections and one shearing section; the second mixing zone includes one conveying section and one shearing section.

[0016] Further, the length of the short-cut fibers fed in the second step is 3 - 8 mm.

[0017] Further, the screw rotation speed of the twin-screw extruder is 200 - 500 rpm.

[0018] Beneficial effects of the present invention: In the present invention, the content of short-cut fibers is increased, and at the same time, the component ratio of the resin mixture is optimized, so that the short-cut fibers can be evenly dispersed in the resin mixture; at the same time, the twin-screw structure is optimized, so that during the extrusion process of the short-cut fibers, the shearing degree is controlled as much as possible to make the lengths of the short-cut fibers uniform. The finally obtained fiber-reinforced thermoplastic plastic particles have a smooth surface and a dense interior, and the tensile strength and tensile modulus of the subsequently prepared thermoplastic composite parts can be significantly improved simultaneously. Description of the Drawings

[0019] Attached Figure 1 is a partial schematic diagram of the screw combination of the twin-screw extruder of the present invention; Attached Figure 2 is a schematic diagram of the screw structure of the conveying section; Attached Figure 3 is a front view of the shearing disc structure; Attached Figure 4 is a left view of the shearing disc structure; Attached Figure 5 is a photograph of the appearance of the high-modulus fiber-reinforced thermoplastic composite particles obtained in Example 1; Attached Figure 6 is a photograph of the appearance of the high-modulus fiber-reinforced thermoplastic composite particles obtained in Example 2; Attached Figure 7 is a photograph of the appearance of the fiber-reinforced thermoplastic composite particles obtained in Comparative Example 1; Attached Figure 8 is a photograph of the appearance of the fiber-reinforced thermoplastic composite before pelletizing obtained in Comparative Example 2; Attached Figure 9 is an electron micrograph of the fiber length distribution in the high-modulus fiber-reinforced thermoplastic composite particles obtained in Example 1; Attached Figure 10 is an electron micrograph of the fiber length distribution in the high-modulus fiber-reinforced thermoplastic composite particles obtained in Example 2; AttachedFigure 11 The fiber length distribution diagram of the fiber-reinforced thermoplastic composite particles obtained in Comparative Example 1; Wherein: 1 - main feed port, 2 - side feed port, 3 - first mixing zone, 4 - second mixing zone, 5 - first conveying section, 6 - shear disc. Detailed implementation manners

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0022] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "connected", "installed", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in combination with specific situations.

[0023] A high-strength and high-modulus fiber-reinforced thermoplastic composite particle, by weight percentage of raw materials, includes: Short-cut fibers, 30 - 60%; Matrix resin, 40 - 70%; Antioxidant, 0 - 1%; Lubricant, 0 - 1%; Compatibilizer, 0 - 5%.

[0024] The average length of the short-cut fibers in the high-strength and high-modulus fiber-reinforced thermoplastic composite particles is 100 - 500 μm.

[0025] The matrix resin is any one or a mixture of several of polyolefin, polyamide (semi-aromatic), polyester, high-temperature nylon, liquid crystal polymer, polyphenylene sulfide, and polyether ether ketone.

[0026] The antioxidant is one or a mixture of several of 2,6-di-tert-butyl-p-cresol, 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, ditrimethyleneglycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], n-octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine, tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, pentaerythritol diphosphite dioctadecyl ester, distearyl thiodipropionate; distearyl thiodipropionate, etc.

[0027] The lubricant is one or a mixture of several of polyethylene wax, silicone oil, silicone rubber, erucamide, pentaerythritol stearate, aluminum distearate, calcium stearate, magnesium stearate, zinc stearate, silicone powder, sodium stearate, stearamide, stearic acid, paraffin wax, etc.

[0028] The compatibilizer is one or a mixture of several of maleic anhydride grafted PP, maleic anhydride grafted PE, maleic anhydride grafted PA6, maleic anhydride grafted POE, maleic anhydride grafted AS, maleic anhydride grafted PPO, glycidyl methacrylate grafted ethylene-propylene copolymer, glycidyl methacrylate grafted POE, glycidyl methacrylate grafted ethylene copolymer, glycidyl methacrylate grafted ethylene-acrylate copolymer, etc.

[0029] The chopped fiber is any one or several of carbon fiber, glass fiber, stainless steel fiber, and basalt fiber.

[0030] Based on the above preparation method of high-strength and high-modulus fiber-reinforced thermoplastic composite particles, it includes the following steps: Step 1: Add the matrix resin, antioxidant, lubricant, and compatibilizer into a high-speed mixer according to the weight percentage of raw materials for premixing to form a resin mixture. Step 2: Feed the premixed resin mixture into the main feeding port of a twin-screw extruder, and feed the chopped fiber into the side feeding port of the twin-screw extruder according to the weight parts of the raw materials. Step 3: After the resin and the chopped fiber are fully mixed, extrude and pelletize to obtain high-strength and high-modulus fiber-reinforced thermoplastic composite particles.

[0031] Further, the twin-screw combination in the twin-screw extruder includes two co-rotating intermeshing screws. Refer to the appendix Figure 1 , which shows a schematic diagram of the partial structure of the twin-screw combination (showing one screw), the twin-screws include a main feeding port 1, a side feeding port 2, a first mixing zone 3, and a second mixing zone 4. The first mixing zone 3 includes a first conveying section 5, a second conveying section, and a shearing section along the conveying direction; the second mixing zone 4 includes a conveying section and a shearing section along the conveying direction.

[0032] As shown in the appendix Figure 2 , the screw length L of the first conveying section 5 in the first mixing zone 3 is 45 - 50 mm, and the screw lead D is 45 - 50 mm; the screw length L of the second conveying section in the first mixing zone is 30 - 35 mm; the screw lead D is 30 - 35 mm.

[0033] The shearing section of the first mixing zone includes a first shearing disk 6 and a second shearing disk with equal lengths in the output direction; as shown in the appendix Figure 3 - 4 , the included angle α of the first shearing disk 6 is 45°, and the length is 48 mm; the included angle α of the second shearing disk is 60°, and the length is 48 mm; The conveying section of the second mixing zone has a screw length of 30 - 35 mm and a screw lead of 30 - 35 mm; the shearing section of the second mixing zone includes a first shearing disk, a second shearing disk, a third shearing disk, and a fourth shearing disk; the included angle α of the first shearing disk is 45°, and the length is 48 mm, the included angle α of the second shearing disk is 60°, and the length is 32 mm; the included angle α of the third shearing disk is 60°, and the length is 48 mm, the included angle α of the fourth shearing disk is 45°, and the length is 48 mm.

[0034] The length-diameter ratio of the screw is 30:1 - 50:1.

[0035] The screw rotation speed of the twin-screw extruder is 100 - 500 rpm.

[0036] The length of the chopped fibers fed in the second step is 3 - 8 mm. Example 1

[0037] A high-strength and high-modulus fiber-reinforced thermoplastic composite particle, by weight percentage of raw materials, includes: Chopped fibers, specifically chopped carbon fibers, with a weight percentage of 42%; Matrix resin, specifically MXD6, with a weight percentage of 57%; Antioxidant, specifically antioxidant 1098 (N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine), 0.3%; Lubricant, specifically calcium stearate, 0.5%; Compatibilizer, specifically glycidyl methacrylate grafted ethylene-propylene copolymer, 0.2%.

[0038] The average length of the chopped carbon fibers in the high modulus fiber reinforced thermoplastic composite particles is 229 μm.

[0039] The preparation method of the high modulus fiber reinforced thermoplastic composite particles in this example includes: Step 1: Add the matrix resin, antioxidant, lubricant, and compatibilizer according to the raw material weight percentage into a high-speed mixer for premixing to form a resin mixture; Step 2: Feed the premixed resin mixture into the main feeding port of a twin-screw extruder, and feed 3-8 mm chopped carbon fibers from the side feeding port of the twin-screw extruder according to the raw material weight parts; the screw speed is 500 rpm; Step 3: After the resin and the chopped fibers are fully mixed, extrude and pelletize to obtain high-strength and high-modulus fiber reinforced thermoplastic composite particles.

[0040] In this example, continuous preparation of the particles can be achieved, and the appearance of the particles is smooth and the cross-section is dense. See the attached Figure 5 . Example 2

[0041] A kind of high-strength and high-modulus fiber reinforced thermoplastic composite particles, according to the raw material weight percentage, includes: Chopped fibers, specifically chopped carbon fibers, 50%; Matrix resin, specifically MXD6, 48% Antioxidant, specifically antioxidant 1098 (N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine), 0.2%; Lubricant, specifically calcium stearate, 0.8%; Compatibilizer, specifically glycidyl methacrylate grafted ethylene-propylene copolymer, 1%.

[0042] The average length of the chopped carbon fibers in the high modulus fiber reinforced thermoplastic composite particles is 333 μm.

[0043] The preparation method of the high modulus fiber reinforced thermoplastic composite particles in this example includes: Step 1: Add the matrix resin, antioxidant, lubricant, and compatibilizer according to the raw material weight percentage into a high-speed mixer for premixing to form a resin mixture; Step 2: Feed the premixed resin mixture into the main feeding port of a twin-screw extruder, and feed chopped fibers from the side feeding port of the twin-screw extruder according to the raw material weight parts; the screw speed is 400 rpm; Step 3: After the resin and the chopped fibers are fully mixed, they are extruded and pelletized to obtain high-strength and high-modulus fiber-reinforced thermoplastic composite particles.

[0044] In this example, continuous preparation of the particles can be achieved, and the appearance of the particles is smooth and the cross-section is dense. See the particle photo in Figure 6 .

[0045] Comparative Example 1 As a comparative example of Example 1, the difference is that the screw speed is 600 rpm.

[0046] In this example, continuous preparation of the particles can basically be achieved, and the appearance of the particles is smooth and the cross-section is dense. See the particle photo in Figure 7 .

[0047] Comparative Example 2 As a comparative example of Example 2, the difference is that the screw speed is 180 rpm.

[0048] During the preparation process of this example, stable strip pulling cannot be achieved (strip breakage occurs), and blockage occurs at the discharge holes of the extruder die head, making continuous preparation impossible; in addition, the appearance of the fiber-reinforced thermoplastic composite strips obtained shows a burr state. See the specific appearance photo in Figure 7 . When the strips in this state are pelletized and then used for injection molding of composite parts, bridging and other situations will occur during feeding, which is not conducive to subsequent injection molding of composite parts.

[0049] Performance comparison: (1) Mechanical property test: The particles obtained in Examples 1-2 and Comparative Examples 1-2 are injection molded, and test specimens are prepared according to the ISO527-1A standard and tested for tensile strength and tensile modulus. The results are shown in Table 3: Table 3 Test item Example 1 Example 2 Comparative example 1 Comparative example 2 Tensile strength (MPa) 225 280 180 290 Tensile modulus (GPa) 49.5 51 48 50 (2) Test of the length of chopped fibers in the particles: The particles obtained in Examples 1-2 and Comparative Example 1 are respectively placed in a muffle furnace for heating and combustion to remove the resin part, leaving the chopped carbon fibers. Observation is carried out under an optical microscope. See the photo in Appendix Figure 9 - 11 . In Example 1, the length distribution of the chopped carbon fibers is relatively uniform, and the average fiber length is 229 μm. In Example 2, the average length of the chopped carbon fibers is 241 μm; while in Comparative Example 1, the length distribution of the carbon fibers is polarized, and there is a large part of extremely short carbon fibers, with an average fiber length of 160 μm.

[0050] Obviously, the above embodiments are merely examples given for clearly explaining the present invention, rather than limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or alterations can be made based on the above description. It is not necessary and impossible to exhaust all implementation manners here, and the obvious changes and alterations derived therefrom still fall within the protection scope of the present invention.

Claims

1. A high-strength and high-modulus fiber-reinforced thermoplastic composite material particle, characterized in that: Calculated by weight percentage of raw materials, including: chopped fibers, 30-60%; Base resin, 40-70%; Antioxidants, 0-1%; Lubricant, 0-1%; Compatibilizer, 0-5%; The average length of the short-cut fibers in the particles is 200-500 μm.

2. The high-strength and high-modulus fiber-reinforced thermoplastic composite material particles according to claim 1, characterized in that: The matrix resin is any one of polyolefin, polyamide (semi-aromatic), polyester, high-temperature nylon, liquid crystal polymer, polyphenylene sulfide, and polyetheretherketone, or a mixture of several of them.

3. The high-strength and high-modulus fiber-reinforced thermoplastic composite material particles according to claim 1, characterized in that: The antioxidant is one or a mixture of 2,6-di-tert-butyl-p-cresol, 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate], tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, tris[2,4-di-tert-butylphenyl] phosphite, bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, dioctadecyl pentaerythritol diphosphite, distearyl thiodipropionate, and dioctadecyl thiodipropionate.

4. The high-strength and high-modulus fiber-reinforced thermoplastic composite material particles according to claim 1, characterized in that: The lubricant is one or a mixture of polyethylene wax, silicone oil, silicone rubber, erucamide, pentaerythritol stearate, aluminum distearate, calcium stearate, magnesium stearate, zinc stearate, silicone powder, sodium stearate, stearamide, stearic acid, paraffin, etc.

5. The high-strength and high-modulus fiber-reinforced thermoplastic composite material particles according to claim 1, characterized in that: The compatibilizer is one or a mixture of maleic anhydride grafted PP, maleic anhydride grafted PE, maleic anhydride grafted PA6, maleic anhydride grafted POE, maleic anhydride grafted AS, maleic anhydride grafted PPO, methacrylic acid glycidyl ether grafted ethylene propylene copolymer, methacrylic acid glycidyl ether grafted POE, methacrylic acid glycidyl ether grafted ethylene copolymer, methacrylic acid glycidyl ether grafted ethylene acrylate copolymer, etc.

6. The high-strength and high-modulus fiber-reinforced thermoplastic composite material particles according to claim 1, characterized in that: The chopped fibers are any one or more of carbon fibers, glass fibers, stainless steel fibers, and basalt fibers.

7. A method for preparing high-strength and high-modulus fiber-reinforced thermoplastic composite particles, based on the composite particles according to any one of claims 1 to 7, characterized in that: include: Step 1: adding the base resin, antioxidant, lubricant and compatibilizer into a high-speed mixer according to the weight percentage of the raw materials for premixing to form a resin mixture; Step 2: feeding the premixed resin mixture from the main feeding port of the twin-screw extruder, and feeding the chopped fibers from the side feeding port of the twin-screw extruder according to the weight of the raw materials; Step 3: Extrusion and pelletizing.

8. The method for preparing high-strength and high-modulus fiber-reinforced thermoplastic composite particles according to claim 7, characterized in that: The aspect ratio of the screw in the twin-screw extruder is 30:1-50:1; the screw speed of the twin-screw extruder is 200-500rpm.

9. The method for preparing high-strength and high-modulus fiber-reinforced thermoplastic composite particles according to claim 7, characterized in that: The screw in the extruder includes a first mixing zone and a second mixing zone. The first mixing zone includes two conveying sections and a shearing section; the second mixing zone includes a conveying section and a shearing section.

10. The method for preparing high-strength and high-modulus fiber-reinforced thermoplastic composite material particles according to claim 7, characterized in that: The length of the chopped fibers fed in step 2 is 3-8 mm.

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