A short-cut glass fiber reinforced polypropylene composite material and a method for preparing the same

Abstract

The application provides a short-cut glass fiber reinforced polypropylene composite material and a preparation method thereof, and comprises the following raw materials in parts by weight: 29-52 parts of polypropylene, 30-50 parts of short-cut glass fiber, 7-10 parts of microcapsule inorganic filler, 1-4 parts of lubricant, and 1-3 parts of compatibilizer; the microcapsule inorganic filler which is compatible with the polypropylene composite material system is prepared by coating the inorganic filler which is surface modified by stearic acid with a copolymer of styrene, butadiene and unsaturated silane as a capsule wall through a dispersion polymerization method; the inorganic filler is selected from one or a combination of two or more of calcium carbonate, barium sulfate, montmorillonite, kaolin, mica, magnesium hydroxide, aluminum hydroxide and wollastonite; the microcapsule inorganic filler can not only improve the uniformity of the distribution of the inorganic filler in the polypropylene composite material system and improve the strength, but also has a toughening effect on the copolymer capsule wall, so that the brittle adverse effect caused by the inorganic filler is eliminated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polypropylene composite materials, and particularly relates to a short glass fiber reinforced polypropylene composite material and a preparation method thereof. BACKGROUND

[0002] Glass fiber reinforced polypropylene has the advantages of high strength, good heat resistance, good wear resistance, low price and the like. The excellent comprehensive performance makes it comparable to engineering plastics, and thus it is widely applied in the fields of electrical appliances, electronics, automobiles, petroleum chemical industry and the like.

[0003] Short fiber reinforced polypropylene is paid more and more attention due to its easier processing, lower cost and more excellent mechanical properties than long glass fiber reinforced polypropylene. Melt extrusion and injection molding are common methods. Patent CN111320811B discloses a short glass fiber reinforced polypropylene composite material and a preparation method. The composite material mainly comprises a polypropylene base resin, an ultrahigh melt index polypropylene resin, short glass fibers, an antioxidant and a compatibilizer. Patent CN112852051B discloses a high-temperature and high-humidity resistant short glass fiber reinforced polypropylene composite material and a preparation method. The raw material components include a polypropylene resin, glass fibers, a maleic anhydride grafting product, a pigment, a hindered phenolic antioxidant and an amine antioxidant.

[0004] The above short glass fiber reinforced polypropylene composite material not only improves the mechanical properties of polypropylene, but also endows the polypropylene composite material with good heat resistance and creep resistance. However, due to the large aspect ratio of the short glass fibers, the polypropylene reinforced by the glass fibers has strong molecular chain orientation, which causes a large difference in shrinkage rate in the flow direction and the vertical flow direction during the injection molding process. This significant anisotropy can cause serious warping deformation of the material, which limits the application of the short glass fiber reinforced polypropylene in some thin mechanical parts and other parts with high requirements for dimensional precision and flatness. The traditional solution is to add some isotropic inorganic fillers, which can improve the deformation degree, but also increases the brittleness of the composite material.

[0005] Therefore, it is necessary to develop a short glass fiber reinforced polypropylene composite material with good warping deformation resistance and toughness. SUMMARY

[0006] To solve the above technical problems, the application provides a short-cut glass fiber reinforced polypropylene composite material and a preparation method thereof.

[0007] To achieve the above object, the following technical scheme is adopted:

[0008] The short-cut glass fiber reinforced polypropylene composite material comprises the following raw materials in parts by weight: 29-52 parts of polypropylene, 30-50 parts of short-cut glass fiber, 7-10 parts of microcapsule inorganic filler, 1-4 parts of lubricant, and 1-3 parts of compatibilizer.

[0009] Further, the inorganic filler is aluminum hydroxide.

[0010] The mass ratio of the stearic acid surface modified inorganic filler, styrene, butadiene and unsaturated silane is 0.7-1:3-4:3-4:3-4.

[0011] Further, the unsaturated silane is selected from one or more of 2-allyltrimethylsilane, trimethylsilene, allyl(tert-butyl)dimethylsilane, isobutenyltrimethylsilane, dimethylphenylvinylsilane, 3-butenyltrimethylsilane, triethylvinylsilane, trimethyl(4-vinylphenyl)silane and allyltriethylsilane, and preferably is 2-allyltrimethylsilane.

[0012] The inventors find that the copolymer formed by styrene, butadiene and unsaturated silane as the capsule wall material of the microcapsule inorganic filler endows the microcapsule inorganic filler with elasticity, can buffer external force, eliminate the brittle adverse effects caused by the use of inorganic fillers, and has no adverse effects on other properties.

[0013] The microcapsule inorganic filler is prepared by the following method:

[0014] 1) stearic acid surface modified inorganic filler: add the inorganic filler to water, ultrasonicate to obtain a suspension, heat, and add molten stearic acid while stirring to react, filter while hot after the reaction is completed, wash with hot anhydrous ethanol, dry, grind, sieve, and reserve;

[0015] 2) Microcapsule coating: under inert atmosphere, the mixture of stabilizer, emulsifier, ethanol, water was heated and mixed uniformly, then the surface modified inorganic filler obtained in step 1) was added and ultrasonically dispersed to get a dispersion, initiator was added and stirred uniformly, the mixture of styrene, butadiene, unsaturated silane was added dropwise, after the dropwise addition was completed, the reaction was carried out under temperature control, after the reaction was completed, the microcapsule inorganic filler was obtained by filtering, washing, drying, extraction and drying.

[0016] Further, the mass ratio of the stearic acid surface modified inorganic filler in step 1) to the mixture of styrene, butadiene, unsaturated silane in step 2) is 0.7-1:10.

[0017] Further, the solid content of the suspension in step 1) is 3-5wt%, the amount of stearic acid is 1-3wt% of the inorganic filler, the heating is to 80-100℃, the reaction time is 1-3h, and the washing times is 1-3 times;

[0018] Further, the stabilizer in step 2) is selected from one or a combination of polyvinylpyrrolidone and polyethylene glycol, the weight average molecular weight of the polyvinylpyrrolidone is 20000-50000g / mol, the weight average molecular weight of the polyethylene glycol is 4000-8000g / mol, the amount of the stabilizer is 1-3wt% of the total amount of the mixture of styrene, butadiene, and unsaturated silane, the mass ratio of the ethanol to water is 5-7:3-5, the emulsifier is selected from one or a combination of dodecylphenol polyoxyethylene ether and cetyltrimethylammonium bromide, the amount of the emulsifier is 1-3wt% of the total amount of the mixture of styrene, butadiene, and unsaturated silane, the solid content of the dispersion is 1-2wt%, the heating is to 60-80℃, the initiator is selected from one or a combination of two or more of azobisisobutyronitrile, dibenzoyl peroxide, benzoyl peroxide, dicumyl peroxide, and diisooctyl phenyl peroxide, the amount of the initiator is 0.5-2wt% of the total amount of the mixture of styrene, butadiene, and unsaturated silane, the mixture of styrene, butadiene, and unsaturated silane is added dropwise within 1-5h, the stirring condition is stirring at a rotation speed of 300-500r / min, the temperature control is to control the temperature at 70-90℃, the reaction time is 12-36h, and the extraction solvent is selected from one or a combination of two or more of benzene, xylene, tetrahydrofuran, and dichloromethane, and the extraction time is 12-48h.

[0019] Since the polypropylene processing fluidity is poor when a large amount of short-cut glass fiber with large aspect ratio is used to reinforce the polypropylene, the polypropylene molecular chain is prone to orientation under the action of the short-cut glass fiber, resulting in anisotropy, the inorganic filler coated by the microcapsule in the application has good compatibility with the polypropylene composite material, can be well mixed with the short-cut glass fiber in the polypropylene matrix, can play a role similar to a "lubricant", can reduce the entanglement of the polypropylene molecular chain with the short-cut glass fiber, improve the mobility of the polypropylene molecular chain, and reduce the influence of the short-cut glass fiber on the orientation of the polypropylene molecular chain, and reduce the warpage deformation.

[0020] The average particle size of the inorganic filler is 20-100 nm.

[0021] The lubricant is polytetrafluoroethylene modified polyethylene wax, the average particle size is 5-15 μm, and the melting point is 110-130 ℃. The polytetrafluoroethylene modified polyethylene wax is usually used as a solid lubricant, can be blended with the resin, and the addition amount is 5-20 wt% of the resin. The inventor finds that the polytetrafluoroethylene modified polyethylene wax has a synergistic effect of the microcapsule inorganic filler in reducing the warpage deformation of the polypropylene composite material.

[0022] The polypropylene melt index is 3-12 g / 10 min.

[0023] The short-cut glass fiber has a diameter of 5-15 μm and a short-cut length of 0.2-10 mm.

[0024] The compatibilizer is selected from one or a combination of maleic anhydride grafted polypropylene and maleic anhydride grafted polyethylene.

[0025] Further, the compatibilizer is maleic anhydride grafted polypropylene, and the grafting rate is 0.3-1.2 wt%.

[0026] The application also provides a preparation method of the short-cut glass fiber reinforced polypropylene composite material, which comprises the following steps:

[0027] The polypropylene, the microcapsule inorganic filler, the lubricant, and the compatibilizer are uniformly mixed, then added to a double-screw extruder from a main feeding bin, and then the short-cut glass fiber is added to the double-screw extruder from a side feeding bin for extrusion granulation.

[0028] The length-diameter ratio of the double-screw extruder is 30-40, the main machine rotation speed is 100-300 r / min, the temperature of the first zone is 160-180 ℃, the temperature of the second zone is 180-200 ℃, the temperature of the third zone is 190-200 ℃, the temperature of the fourth zone is 190-210 ℃, the temperature of the fifth zone is 190-210 ℃, the temperature of the sixth zone is 190-210 ℃, the temperature of the seventh zone is 190-210 ℃, the temperature of the eighth zone is 190-210 ℃, the temperature of the ninth zone is 190-220 ℃, and the temperature of the die head is 190-220 ℃.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] The present application coats the surface-modified inorganic filler of stearic acid by a dispersion polymerization method with a copolymer of styrene, butadiene and unsaturated silane as the capsule wall to obtain a microcapsule inorganic filler which is compatible with a polypropylene composite system. The microcapsule inorganic filler can not only improve the uniformity of the distribution of the inorganic filler in the polypropylene composite system and the strength, but also has a toughening effect and eliminates the brittle adverse effects caused by the inorganic filler. DETAILED DESCRIPTION

[0031] The present application will be further described below in conjunction with specific examples, but is not limited to the contents of the description. Unless otherwise specified, the "parts" in the examples of the present application are all by weight. The reagents used are all commercially available reagents in the art.

[0032] Aluminum hydroxide was purchased from Xuancheng Jingrui New Material Co., Ltd., model number VK-LA50, average particle size 50 nm.

[0033] Magnesium hydroxide was purchased from Xuancheng Jingrui New Material Co., Ltd., model number VK-MHT01, average particle size 50 nm.

[0034] Barium sulfate was purchased from Zhongke Jinian (Beijing) Technology Co., Ltd., average particle size 50 nm.

[0035] Polypropylene SP179, melt index 8 g / 10 min, Yanshan Petrochemical Co., Ltd.

[0036] Polytetrafluoroethylene modified polyethylene wax, average particle size 9.5 μm, melting point 1250℃.

[0037] Maleic anhydride grafted polypropylene was purchased from Nantong Rizhisheng New Material Co., Ltd., grafting rate 0.8 wt%.

[0038] Chopped glass fiber was purchased from Shenzhen Yataida Technology Co., Ltd., model number ECS-11-4.5, type: no alkali, diameter 11 μm, chopped length 4.5 μm.

[0039] Polyethylene wax, weight average molecular weight 3000 g / mol, purchased from Jiangyin Gushandongfeng Synthetic Chemical Co., Ltd.

[0040] Polyvinylpyrrolidone, weight average molecular weight 24000 g / mol, purchased from Shanghai Chuangsaite Science and Technology Co., Ltd.

[0041] Microcapsule inorganic filler

[0042] Preparation Example 1

[0043] 1) Surface modification of aluminum hydroxide: 5 g of aluminum hydroxide was added to 95 g of water, and a suspension was obtained by ultrasonic treatment. The mixture was heated to 90°C, and 0.15 g of stearic acid was added while stirring to carry out the reaction. After the reaction was completed, the mixture was filtered while hot, washed with 60°C anhydrous ethanol three times, dried, ground, and sieved to obtain a product.

[0044] 2) Microcapsule coating: A mixture of 0.2 g of polyvinylpyrrolidone, 0.3 g of dodecylphenol polyoxyethylene ether, 50 g of ethanol, and 50 g of water was heated and mixed uniformly under a nitrogen atmosphere. Then, 0.7 g of the surface-modified aluminum hydroxide obtained in step 1) was added, and a dispersion was obtained by ultrasonic treatment. 0.1 g of azobisisobutyronitrile was added and stirred uniformly. 4 g of styrene, 3 g of butadiene, and 3 g of 2-allyltrimethylsilane were added dropwise within 3 h. After the dropwise addition was completed, the mixture was stirred at a rotation speed of 400 r / min and controlled to 80°C to carry out the reaction for 24 h. After the reaction was completed, the mixture was filtered, washed, dried, extracted with xylene for 24 h, and dried to obtain a microcapsule inorganic filler.

[0045] Preparation Example 2

[0046] The rest was the same as in Preparation Example 1, except that an equal amount of allyl(tert-butyl)dimethylsilane was used instead of 2-allyltrimethylsilane.

[0047] Preparation Example 3

[0048] The rest was the same as in Preparation Example 1, except that an equal amount of magnesium hydroxide was used instead of aluminum hydroxide.

[0049] Preparation Example 4

[0050] The rest was the same as in Preparation Example 1, except that an equal amount of barium sulfate was used instead of aluminum hydroxide.

[0051] Preparation Example 5

[0052] The rest was the same as in Preparation Example 1, except that the amount of surface-modified aluminum hydroxide used in step 2) was 1 g.

[0053] Preparation Example 6

[0054] The rest was the same as in Preparation Example 1, except that the amount of styrene used was 3 g, the amount of butadiene used was 3 g, and the amount of 2-allyltrimethylsilane used was 4 g.

[0055] Preparation Example 7

[0056] The rest was the same as in Preparation Example 1, except that the amount of styrene used was 3 g, the amount of butadiene used was 4 g, and the amount of 2-allyltrimethylsilane used was 3 g.

[0057] Comparative Preparation Example 1

[0058] The rest is the same as Preparation Example 1, except that equal mass of styrene is used to replace 2-allyltrimethylsilane.

[0059] Preparation of polypropylene composite material

[0060] Example 1

[0061] 32 g of polypropylene, 10 g of the microcapsule inorganic filler prepared in Preparation Example 1, 1 g of polytetrafluoroethylene modified polyethylene wax, and 3 g of maleic anhydride grafted polypropylene are mixed uniformly, and then added to a twin-screw extruder from a main feeding bin, and 50 g of chopped glass fiber is added to the twin-screw extruder from a side feeding bin for extrusion granulation.

[0062] The length-diameter ratio of the twin-screw extruder is 36, the main machine speed is 260 r / min, the temperature of the first zone is 160℃, the temperature of the second zone is 180℃, the temperature of the third zone is 190℃, the temperature of the fourth zone is 200℃, the temperature of the fifth zone is 210℃, the temperature of the sixth zone is 210℃, the temperature of the seventh zone is 210℃, the temperature of the eighth zone is 210℃, the temperature of the ninth zone is 220℃, and the temperature of the die head is 220℃.

[0063] Examples 2-7

[0064] The rest is the same as Example 1, except that equal mass of the microcapsule inorganic filler prepared in Preparation Examples 2-7 is used to replace the microcapsule inorganic filler prepared in Preparation Example 1.

[0065] Example 8

[0066] The rest is the same as Example 1, except that the amount of the microcapsule inorganic filler prepared in Preparation Example 1 is 7 g, and the amount of polytetrafluoroethylene modified polyethylene wax is 4 g.

[0067] Example 9

[0068] The rest is the same as Example 1, except that the amount of polypropylene is 52 g, and the amount of chopped glass fiber is 30 g.

[0069] Example 10

[0070] The rest is the same as Example 1, except that equal mass of polyethylene wax is used to replace polytetrafluoroethylene modified polyethylene wax.

[0071] Comparative Example 1

[0072] The rest is the same as Example 1, except that equal mass of the microcapsule inorganic filler prepared in Comparative Preparation Example 1 is used to replace the microcapsule inorganic filler prepared in Preparation Example 1.

[0073] Comparative Example 2

[0074] The rest is the same as Example 1, except that the microcapsule inorganic filler prepared in Preparation Example 1 is not added.

[0075] The polypropylene composite materials prepared in the above examples and comparative examples were subjected to the following performance tests:

[0076] Flame retardant performance: referring to standard UL-94, sample thickness 3.2 mm, and recording whether there is a melt dripping phenomenon.

[0077] Tensile performance: referring to standard GB / T 1040.2-2022 Determination of tensile properties of plastics.

[0078] Impact strength: referring to standard ASTM D256-1997 Izod impact performance test of plastics.

[0079] Warpage performance: using an injection molding machine to injection mold a sample with a size of 355 mm x 70 mm x 3.2 mm, placing it at room temperature for 1 day, and referring to standard GB / T4677.5-1984 Test method for warpage of printed boards to test.

[0080] Table 1

[0081]

[0082] " / " represents a flame retardant level lower than V2.

[0083] As can be seen from the impact strength test in Table 1, the microcapsule inorganic filler prepared in the application not only improves the uniformity of the distribution of inorganic fillers in the polypropylene composite material system and improves the strength, but also has a toughening effect on the copolymer capsule wall, eliminating the brittle adverse effects caused by inorganic fillers.

[0084] As can be seen from the warpage performance test of Examples 1 and Comparative Examples 1-3 in Table 1, polytetrafluoroethylene modified polyethylene wax has a significant synergistic effect of microcapsule inorganic filler in reducing the warpage deformation of polypropylene composite material. In addition, as can be seen from the flame retardant performance test, when the inorganic filler is aluminum hydroxide, the "wick effect" of glass fiber reinforced polypropylene composite material is overcome, and the flame retardant performance of the polypropylene composite material is improved.

[0085] The above detailed description is a specific description of one of the feasible embodiments of the application, and this embodiment is not used to limit the patent scope of the application. Any equivalent implementation or change that does not deviate from the application should be included in the scope of the technical solutions of the application.

Claims

1. A short-cut glass fiber reinforced polypropylene composite material, characterized in that, The raw materials include the following parts by weight: 29-52 parts polypropylene, 30-50 parts chopped glass fiber, 7-10 parts microcapsule inorganic filler, 1-4 parts lubricant, and 1-3 parts compatibilizer; the microcapsule inorganic filler uses stearic acid surface-modified inorganic filler as the core and a copolymer of styrene, butadiene, and unsaturated silane as the capsule wall; the inorganic filler is selected from one or a combination of two or more of calcium carbonate, barium sulfate, montmorillonite, kaolin, mica, magnesium hydroxide, aluminum hydroxide, and wollastonite; the stearic acid surface-modified inorganic filler, styrene, butadiene, and... The mass ratio of unsaturated silanes is 0.7-1:3-4:3-4:3-4; the unsaturated silanes are selected from one or a combination of two or more of 2-allyltrimethylsilane, trimethylsilylethylene, allyl (tert-butyl)dimethylsilane, isobutylenyltrimethylsilane, dimethylphenylvinylsilane, 3-butenyltrimethylsilane, triethylvinylsilane, trimethyl (4-vinylphenyl)silane, and allyltriethylsilane; the lubricant is polytetrafluoroethylene modified polyethylene wax with an average particle size of 5-15 μm and a melting point of 110-130℃.

2. The chopped glass fiber reinforced polypropylene composite material according to claim 1, characterized in that, The inorganic filler is aluminum hydroxide.

3. The chopped glass fiber reinforced polypropylene composite material according to claim 1, characterized in that, The microcapsule inorganic filler is prepared by a method comprising the following steps: 1) Stearic acid surface-modified inorganic filler: Add the inorganic filler to water, sonicate to obtain a suspension, heat up, and add molten stearic acid while stirring to react. After the reaction is completed, filter while hot, wash with hot anhydrous ethanol, dry, grind, and sieve for later use. 2) Microcapsule coating: Under an inert atmosphere, a mixture of stabilizer, emulsifier, ethanol, and water is heated and mixed evenly. Then, the surface-modified inorganic filler obtained in step 1) is added, and the mixture is ultrasonically dispersed to obtain a dispersion. An initiator is added and stirred evenly. A mixture of styrene, butadiene, and unsaturated silane is added dropwise. After the addition is complete, the mixture is stirred and the temperature is controlled to carry out the reaction. After the reaction is completed, the mixture is filtered, washed, dried, extracted, and dried to obtain the microcapsule inorganic filler.

4. The chopped glass fiber reinforced polypropylene composite material according to claim 3, characterized in that, Step 2) The solid content of the dispersion is 1-2 wt%, the temperature is raised to 60-80℃, the mixture of styrene, butadiene and unsaturated silane is added dropwise within 1-5 hours, the stirring conditions are stirring at a speed of 300-500 r / min, the temperature is controlled at 70-90℃, and the reaction time is 12-36 hours.

5. The chopped glass fiber reinforced polypropylene composite material according to claim 1, characterized in that, The average particle size of the inorganic filler is 20-100 nm.

6. The chopped glass fiber reinforced polypropylene composite material according to claim 1, characterized in that, The chopped glass fibers have a diameter of 5-15 μm and a chopped length of 0.2-10 mm.

7. The method for preparing the chopped glass fiber reinforced polypropylene composite material according to any one of claims 1-6, characterized in that, Includes the following steps: Polypropylene, microcapsule inorganic filler, lubricant, and compatibilizer are mixed evenly and then fed into the twin-screw extruder from the main feed hopper. Short glass fibers are then fed into the twin-screw extruder from the side feed hopper for extrusion granulation.

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