Anti-warping glass fiber reinforced polypropylene material and preparation method thereof

Abstract

The invention discloses an anti-warping glass fiber reinforced polypropylene material and a preparation method thereof. The anti-warping glass fiber reinforced polypropylene material is prepared from 47-84.5 parts by weight of polypropylene, 10-40 parts by weight of glass fiber, 2-6 parts by weight of a coupling agent, 3-6 parts by weight of ultra-high molecular weight polyethylene, 0.2-0.5 part by weight of an antioxidant and 0.3-0.5 part by weight of a light stabilizer. Wherein the ultra-high molecular weight polyethylene is branched chain-free linear polyethylene with the number-average molecular weight of 1.5 million or more. The glass fiber reinforced polypropylene material disclosed by the invention has relatively low transverse and longitudinal shrinkage rate difference, and the warping condition of a workpiece can be obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to an anti-warping glass fiber reinforced polypropylene material and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is a thermoplastic resin made by polymerizing propylene monomers. It is widely used for its low density, high strength and good chemical stability.

[0003] By adding glass fiber to polypropylene resin, the rigidity and thermal stability of polypropylene materials can be improved, and it is widely used in structural parts and high-heat-resistant parts of automobiles and home appliances. However, polypropylene itself is a crystalline material with a large shrinkage rate, and glass fiber is a filler with a high aspect ratio. In the direction of glass fiber distribution, the glass fiber hinders the shrinkage of polypropylene, so it has a very low shrinkage rate. In the subsequent injection molding process, due to the obvious orientation of glass fiber, the product has a significant difference in shrinkage rate in the direction of glass fiber flow and perpendicular to the direction of glass fiber flow, which will cause product warping. Especially in thinner flat parts or parts with high surface flatness requirements, the application of glass fiber reinforced polypropylene materials is limited. Summary of the invention

[0004] In view of this, the primary purpose of the present invention is to provide a warping-resistant glass fiber reinforced polypropylene material, by adding ultra-high molecular weight polyethylene (molecular weight above 1.5 million) to the polypropylene system. The molecular chain of the polyethylene is very long, and curling and entanglement may occur in the product after injection molding, thereby preventing the orientation of the glass fiber to a certain extent, reducing the difference in shrinkage rate between the flow direction and the direction perpendicular to the flow, and improving the warping of the material after injection molding.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides an anti-warping glass fiber reinforced polypropylene material, which is prepared by weight from 47 to 84.5 parts of polypropylene, 10 to 40 parts of glass fiber, 2 to 6 parts of coupling agent, 3 to 6 parts of ultra-high molecular weight polyethylene, 0.2 to 0.5 parts of antioxidant and 0.3 to 0.5 parts of light stabilizer;

[0007] The ultra-high molecular weight polyethylene is an unbranched linear polyethylene with a number average molecular weight of more than 1.5 million.

[0008] In the glass fiber reinforced polypropylene system of the present invention, ultra-high molecular weight polyethylene with a number average molecular weight of more than 1.5 million is added, and the advantage of its long molecular chain is utilized to cause curling and entanglement in the product after injection molding, thereby preventing the orientation of the glass fiber to a certain extent, reducing the difference in shrinkage rate between the flow direction and the direction perpendicular to the flow direction, and improving the warpage of the material after injection molding.

[0009] In the present invention, the number average molecular weight of the ultra-high molecular weight polyethylene is above 1.5 million. If the molecular weight is too low, the molecular chain length is insufficient, and it is not easy to produce the winding effect, and there is no obvious effect on improving the warpage. Preferably, in some specific embodiments of the present invention, the number average molecular weight of the ultra-high molecular weight polyethylene is between 1.5 million and 6 million.

[0010] Furthermore, the polypropylene described in the present invention as the base material is not particularly limited, and conventional copolymer polypropylene and homopolymer polypropylene in the art can be used.

[0011] Furthermore, the glass fiber is a chopped glass fiber. In some specific embodiments of the present invention, the fiber length of the chopped glass fiber is 3 to 25 mm, and the fiber diameter is 9 to 13 μm.

[0012] Furthermore, the coupling agent mainly functions to improve the bonding performance between the base polypropylene and the glass fiber. Preferably, the coupling agent is maleic anhydride grafted polypropylene (PP-g-MAH). In some specific embodiments of the present invention, the grafting rate of maleic anhydride in the maleic anhydride grafted polypropylene is 0.5 to 3 wt%.

[0013] Further, the antioxidant and light stabilizer are both relatively common types in the art, without special restrictions. In some specific embodiments of the present invention, the antioxidant is one or a mixture of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, tris(2,4-di-tert-butylphenyl)phosphite. The light stabilizer is a hindered amine light stabilizer.

[0014] The present invention further provides a method for preparing the anti-warping glass fiber reinforced polypropylene material as described above, comprising the following steps:

[0015] 47 to 84.5 parts of polypropylene, 2 to 6 parts of maleic anhydride grafted polypropylene, 3 to 6 parts of ultra-high molecular weight polyethylene, 0.2 to 0.5 parts of antioxidant and 0.3 to 0.5 parts of light stabilizer are mixed uniformly according to weight ratio to obtain a mixture;

[0016] The mixed material is added into the main feeding port of a twin-screw extruder, and 10 to 40 parts of glass fibers are added into the glass fiber port at the same time, and the anti-warping glass fiber reinforced polypropylene material is prepared through melt extrusion, granulation and drying.

[0017] Furthermore, the rotation speed of the twin-screw extruder is 300-600 rpm, and the temperature in the barrel is 200-250°C.

[0018] Beneficial effects of the present invention:

[0019] In the present invention, ultra-high molecular weight polyethylene material is added to the glass fiber reinforced polypropylene system. Since the molecular weight of the material is as high as more than 1.5 million and the molecular chain is very long, curling and entanglement occur in the product after injection molding, thereby preventing the orientation of the glass fiber to a certain extent, reducing the difference in shrinkage rate between the flow direction and the perpendicular flow direction, and improving the warping of the material after injection molding. DETAILED DESCRIPTION

[0020] Embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In addition, unless otherwise specified, methods that do not specifically record conditions or steps are conventional methods, and the reagents and materials used can be obtained from commercial sources.

[0022] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0023] Polypropylene: PP T30S (Yanchang Petroleum), PP YPJ1215C (Yangzi Petrochemical), PP Z30S (Sinopec);

[0024] Glass fiber: Glass fiber-305K-3.0, Chongqing International; Glass fiber-248A, Owens Corning;

[0025] Maleic anhydride grafted polypropylene (PP-G): GPM200A, GPM200B (Ningbo Nengzhiguang);

[0026] Ultra-high molecular weight polyethylene: UHMWPE, GUR 5113 (Celanese, USA), L5000 (Mitsui Chemicals, Japan);

[0027] High-density polyethylene: HDPE 8008 (Sinopec);

[0028] Antioxidants: 1010, 168, Lionon;

[0029] Light stabilizer: V703 (Cytec), 5589 (Xinxiu Chemical).

[0030] Example 1

[0031] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, and its raw material composition is as follows:

[0032]

[0033] The preparation steps are as follows:

[0034] After uniformly mixing polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant and light stabilizer according to weight parts, the mixture is added into a twin-screw extruder from the main material port, and glass fiber is added from the glass fiber port. After melt extrusion, an anti-warping glass fiber reinforced polypropylene material is obtained; wherein, the main engine speed of the twin-screw extruder is 430 rpm, and the temperatures from the feeding section to the die are 220°C, 220°C, 220°C, 220°C, 230°C, 230°C, 230°C, 210°C, 210°C, and 210°C, respectively.

[0035] Example 2

[0036] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, and its raw material composition is as follows:

[0037]

[0038]

[0039] The preparation steps are as follows:

[0040] After uniformly mixing polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant and light stabilizer according to weight parts, the mixture is added into a twin-screw extruder from the main material port, and glass fiber is added from the glass fiber port. After melt extrusion, an anti-warping glass fiber reinforced polypropylene material is obtained; wherein, the main engine speed of the twin-screw extruder is 500 rpm, and the temperatures from the feeding section to the die are 210°C, 210°C, 220°C, 230°C, 230°C, 230°C, 220°C, 220°C, and 210°C respectively.

[0041] Example 3

[0042] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, and its raw material composition is as follows:

[0043]

[0044] The preparation steps are as follows:

[0045] After uniformly mixing polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant and light stabilizer according to weight parts, the mixture is added into a twin-screw extruder from the main material port, and glass fiber is added from the glass fiber port. After melt extrusion, an anti-warping glass fiber reinforced polypropylene material is obtained; wherein, the main engine speed of the twin-screw extruder is 380 rpm, and the temperatures from the feeding section to the die are 220°C, 230°C, 230°C, 240°C, 240°C, 230°C, 230°C, 220°C, 220°C, and 210°C respectively.

[0046] Example 4

[0047] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, and its raw material composition is as follows:

[0048]

[0049]

[0050] The preparation steps are as follows:

[0051] After uniformly mixing polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant and light stabilizer according to weight parts, the mixture is added into a twin-screw extruder from the main material port, and glass fiber is added from the glass fiber port. After melt extrusion, an anti-warping glass fiber reinforced polypropylene material is obtained; wherein, the main engine speed of the twin-screw extruder is 600 rpm, and the temperatures from the feeding section to the die are 230°C, 230°C, 240°C, 240°C, 250°C, 230°C, 230°C, 220°C, 220°C, and 220°C, respectively.

[0052] Example 5

[0053] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, and its raw material composition is as follows:

[0054]

[0055] After uniformly mixing polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant and light stabilizer according to weight parts, the mixture is added into a twin-screw extruder from the main material port, and glass fiber is added from the glass fiber port. After melt extrusion, an anti-warping glass fiber reinforced polypropylene material is obtained; wherein, the main engine speed of the twin-screw extruder is 500 rpm, and the temperatures from the feeding section to the die are 210°C, 210°C, 220°C, 230°C, 230°C, 230°C, 220°C, 220°C, and 210°C respectively.

[0056] Comparative Example 1

[0057] This comparative example provides another glass fiber reinforced polypropylene material, and the other raw materials are as follows:

[0058]

[0059]

[0060] The preparation steps are as follows:

[0061] After uniformly mixing polypropylene, PP-G, antioxidant and light stabilizer according to weight parts, the materials are added into a twin-screw extruder from the main material port, and glass fiber is added from the glass fiber port. After melt extrusion, an anti-warping glass fiber reinforced polypropylene material is obtained; wherein, the main engine speed of the twin-screw extruder is 430 rpm, and the temperatures from the feeding section to the die are 220°C, 220°C, 220°C, 220°C, 230°C, 230°C, 230°C, 210°C, 210°C, and 210°C, respectively.

[0062] Comparative Example 2

[0063] This comparative example provides a glass fiber reinforced polypropylene material, which adopts the same implementation as Example 1, except that UHMW-PE is replaced by an equal weight portion of high-density polyethylene. Other raw material compositions and preparation processes are the same as those in Example 1.

[0064] The raw material composition is as follows:

[0065]

[0066] The preparation steps are as follows:

[0067] Polypropylene, PP-G, high-density polyethylene, antioxidant and light stabilizer are uniformly mixed according to weight parts, and the mixture is added into a twin-screw extruder from the main material port. At the same time, glass fiber is added from the glass fiber port and melt-extruded to obtain an anti-warping glass fiber reinforced polypropylene material. The main engine speed of the twin-screw extruder is 430 rpm, and the temperatures from the feeding section to the die are 220°C, 220°C, 220°C, 220°C, 230°C, 230°C, 230°C, 210°C, 210°C, and 210°C, respectively.

[0068] Performance Testing

[0069] The glass fiber reinforced polypropylene materials prepared in Examples 1-5 and Comparative Examples 1-2 were tested for relevant properties. The test results are shown in Table 1.

[0070] Table 1 Performance test results of glass fiber reinforced polypropylene materials

[0071]

[0072] In Table 1:

[0073] (1) Tensile strength is measured according to ISO 527, with a tensile speed of 5 mm / min.

[0074] (2) Flexural strength and flexural modulus refer to the test standard ISO 178, bending speed 2mm / min.

[0075] (3) Izod notched impact strength is measured in accordance with ISO 180, test conditions: 23°C, molding notch, 1A type molding.

[0076] (4) Shrinkage is measured after injection molding into a square plate with a size of 60×60×2 mm and storing at 23°C for 48 hours. Shrinkage = (molding size - sample size) / molding size, shrinkage difference = shrinkage in the direction perpendicular to the flow - shrinkage in the direction of flow. The warpage is visually observed on the square plate and the result is judged.

[0077] It can be seen from the test results in Table 1 that the glass fiber reinforced polypropylene material in the present invention has a lower difference in transverse and longitudinal shrinkage rates than the traditional glass fiber reinforced polypropylene material, and can significantly improve the warping of the workpiece.

[0078] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A warping-resistant glass fiber reinforced polypropylene material, characterized in that: The invention is prepared from 47 to 84.5 parts of polypropylene, 10 to 40 parts of glass fiber, 2 to 6 parts of coupling agent, 3 to 6 parts of ultra-high molecular weight polyethylene, 0.2 to 0.5 parts of antioxidant and 0.3 to 0.5 parts of light stabilizer according to weight parts; The ultra-high molecular weight polyethylene is an unbranched linear polyethylene with a number average molecular weight of more than 1.5 million.

2. The anti-warping glass fiber reinforced polypropylene material according to claim 1, characterized in that: The polypropylene is at least one of copolymer polypropylene and homopolymer polypropylene.

3. The anti-warping glass fiber reinforced polypropylene material according to claim 1, characterized in that: The glass fibers are chopped glass fibers.

4. The anti-warping glass fiber reinforced polypropylene material according to claim 3, characterized in that: The fiber length of the chopped glass is 3 to 25 mm, and the fiber diameter is 9 to 13 μm.

5. The anti-warping glass fiber reinforced polypropylene material according to claim 1, characterized in that: The coupling agent is maleic anhydride grafted polypropylene; Preferably, in the maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride is 0.5 to 3 wt %.

6. The anti-warping glass fiber reinforced polypropylene material according to claim 1, characterized in that: The number average molecular weight of the ultra-high molecular weight polyethylene is 1.5 million to 6 million.

7. The anti-warping glass fiber reinforced polypropylene material according to claim 1, characterized in that: The antioxidant is one of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester and tris(2,4-di-tert-butylphenyl) phosphite or a mixture of the two.

8. The anti-warping glass fiber reinforced polypropylene material according to claim 1, characterized in that: The light stabilizer is a hindered amine light stabilizer.

9. A method for preparing the anti-warping glass fiber reinforced polypropylene material according to any one of claims 1 to 8, characterized in that: The following steps are involved: 47 to 84.5 parts of polypropylene, 2 to 6 parts of maleic anhydride grafted polypropylene, 3 to 6 parts of ultra-high molecular weight polyethylene, 0.2 to 0.5 parts of antioxidant and 0.3 to 0.5 parts of light stabilizer are mixed uniformly according to weight ratio to obtain a mixture; The mixed material is added into the main feeding port of a twin-screw extruder, and 10 to 40 parts of glass fibers are added into the glass fiber port at the same time, and the anti-warping glass fiber reinforced polypropylene material is prepared through melt extrusion, granulation and drying.

10. The preparation method according to claim 7, characterized in that: The rotation speed of the twin-screw extruder is 300-600 rpm, and the temperature in the barrel is 200-250° C.

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