A warp-resistant glass fiber reinforced polypropylene material and a method for producing the same

Abstract

The application discloses a kind of warp-proof glass fiber reinforced polypropylene materials and preparation method thereof, the warp-proof glass fiber reinforced polypropylene material is prepared by 47~84.5 parts of polypropylene, 10~40 parts of glass fiber, 2~6 parts of coupling agent, 3~6 parts of ultra-high molecular weight polyethylene, 0.2~0.5 parts of antioxidant and 0.3~0.5 parts of light stabilizer according to weight parts;Wherein, the ultra-high molecular weight polyethylene is linear polyethylene without branch with number average molecular weight 1.5 million or more.The glass fiber reinforced polypropylene material in the application has lower transverse and longitudinal shrinkage rate difference, and can significantly improve the warping condition of the workpiece.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to an anti-warping glass fiber reinforced polypropylene material and its preparation method. Background Technology

[0002] Polypropylene (PP) is a thermoplastic resin polymerized from propylene monomers, and it is widely used due to its low density, high strength and good chemical stability.

[0003] Adding glass fibers to polypropylene resin can improve the rigidity and thermal stability of polypropylene materials, making them widely used in structural components and high-heat-resistant parts in automobiles and home appliances. However, polypropylene itself is a crystalline material with a large shrinkage rate, while 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, resulting in a very low shrinkage rate. During subsequent injection molding, the distinct orientation of the glass fiber leads to a significant difference in shrinkage rate between the direction of glass fiber flow and the direction perpendicular to the flow, which can cause product warping. The application of glass fiber reinforced polypropylene materials is particularly limited in thin, flat parts or parts requiring high surface flatness. Summary of the Invention

[0004] In view of this, the primary objective of the present invention is to provide an anti-warping glass fiber reinforced polypropylene material, in which ultra-high molecular weight polyethylene (molecular weight of more than 1.5 million) is added to the polypropylene system. Its molecular chains are very long, and they can curl and entangle in the injection-molded product, thereby preventing the orientation of glass fibers 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.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

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

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

[0008] In this invention, ultra-high molecular weight polyethylene with a number average molecular weight of over 1.5 million is added to the glass fiber reinforced polypropylene system. Taking advantage of its long molecular chain, it curls and wraps within the injection-molded product, 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 warpage of the material after injection molding.

[0009] In this invention, the number average molecular weight of ultra-high molecular weight polyethylene is above 1.5 million. If the molecular weight is too low, the molecular chain length is insufficient, making it difficult to produce an entanglement effect and having no significant effect on improving warpage. Preferably, in some specific embodiments of this invention, the number average molecular weight of ultra-high molecular weight polyethylene is between 1.5 million and 6 million.

[0010] Furthermore, there are no particular limitations on the use of polypropylene as a base material in this invention; conventional copolymer polypropylene and homopolymer polypropylene in the art are both acceptable.

[0011] Furthermore, the glass fiber is chopped glass fiber. In some specific embodiments of the present invention, the fiber length of the chopped glass 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] Furthermore, the antioxidants and light stabilizers mentioned are all relatively conventional types in the art, and there are no particular limitations. In some specific embodiments of the present invention, the antioxidant is one or a mixture of two of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite. The light stabilizer is a hindered amine light stabilizer.

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

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

[0016] The mixture is added to the main feed port of a twin-screw extruder, and 10-40 parts of glass fiber are added to the glass fiber inlet. After melt extrusion, granulation and drying, anti-warping glass fiber reinforced polypropylene material is obtained.

[0017] Furthermore, the twin-screw extruder has a rotational speed of 300–600 rpm and a barrel temperature of 200–250°C.

[0018] The beneficial effects of this invention are:

[0019] In this invention, ultra-high molecular weight polyethylene (UHMWPE) is added to the glass fiber reinforced polypropylene system. Because the molecular weight of this material is as high as 1.5 million or more and the molecular chains are very long, it curls and wraps in the injection-molded product, 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 Implementation

[0020] The 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 commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, unless otherwise specified, methods not specifically describing conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0022] The specific information regarding 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] Fiberglass: Fiberglass-305K-3.0, Chongqing International; Fiberglass-248A, Owens Corning;

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

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

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

[0028] Antioxidants: 1010, 168, and Leyron;

[0029] Light stabilizers: V703 (Cypertech), 5589 (New Star Chemicals).

[0030] Example 1

[0031] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, the raw material composition of which is shown in the table below:

[0032]

[0033] The preparation steps are as follows:

[0034] Polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant, and light stabilizer are mixed evenly according to weight parts and then fed into a twin-screw extruder through the main feed port. At the same time, glass fiber is added through the glass fiber port. After melt extrusion, anti-warping glass fiber reinforced polypropylene material is obtained. The main speed of the twin-screw extruder is 430 rpm, and the temperature from the feeding section to the die head is 220℃, 220℃, 220℃, 220℃, 230℃, 230℃, 230℃, 210℃, 210℃, 210℃.

[0035] Example 2

[0036] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, the raw material composition of which is shown in the table below:

[0037]

[0038]

[0039] The preparation steps are as follows:

[0040] Polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant, and light stabilizer are mixed evenly according to weight parts and then fed into a twin-screw extruder through the main feed port. At the same time, glass fiber is added through the glass fiber port. After melt extrusion, anti-warping glass fiber reinforced polypropylene material is obtained. The main speed of the twin-screw extruder is 500 rpm, and the temperature from the feeding section to the die head is 210℃, 210℃, 220℃, 230℃, 230℃, 230℃, 220℃, 220℃, and 210℃ respectively.

[0041] Example 3

[0042] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, the raw material composition of which is shown in the table below:

[0043]

[0044] The preparation steps are as follows:

[0045] Polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant, and light stabilizer are mixed evenly according to weight parts and then fed into a twin-screw extruder through the main feed port. At the same time, glass fiber is added through the glass fiber port. After melt extrusion, anti-warping glass fiber reinforced polypropylene material is obtained. The main speed of the twin-screw extruder is 380 rpm, and the temperatures from the feeding section to the die head are 220℃, 230℃, 230℃, 240℃, 240℃, 230℃, 230℃, 220℃, 220℃, and 210℃ respectively.

[0046] Example 4

[0047] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, the raw material composition of which is shown in the table below:

[0048]

[0049]

[0050] The preparation steps are as follows:

[0051] Polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant, and light stabilizer are mixed evenly according to weight parts and then fed into a twin-screw extruder through the main feed port. At the same time, glass fiber is added through the glass fiber port. After melt extrusion, anti-warping glass fiber reinforced polypropylene material is obtained. The main speed of the twin-screw extruder is 600 rpm, and the temperature from the feeding section to the die head is 230℃, 230℃, 240℃, 240℃, 250℃, 230℃, 230℃, 220℃, 220℃, 220℃.

[0052] Example 5

[0053] This embodiment provides an anti-warping glass fiber reinforced polypropylene material, the raw material composition of which is shown in the table below:

[0054]

[0055] Polypropylene, PP-G, ultra-high molecular weight polyethylene, antioxidant, and light stabilizer are mixed evenly according to weight parts and then fed into a twin-screw extruder through the main feed port. At the same time, glass fiber is added through the glass fiber port. After melt extrusion, anti-warping glass fiber reinforced polypropylene material is obtained. The main speed of the twin-screw extruder is 500 rpm, and the temperature from the feeding section to the die head is 210℃, 210℃, 220℃, 230℃, 230℃, 230℃, 220℃, 220℃, and 210℃ respectively.

[0056] Comparative Example 1

[0057] This comparative example provides another glass fiber reinforced polypropylene material, the composition of which is shown in the table below:

[0058]

[0059]

[0060] The preparation steps are as follows:

[0061] Polypropylene, PP-G, antioxidant, and light stabilizer are mixed evenly according to weight parts and then fed into a twin-screw extruder through the main feed port. At the same time, glass fiber is added through the glass fiber port. After melt extrusion, anti-warping glass fiber reinforced polypropylene material is obtained. The main speed of the twin-screw extruder is 430 rpm, and the temperature from the feeding section to the die head is 220℃, 220℃, 220℃, 220℃, 230℃, 230℃, 230℃, 210℃, 210℃, 210℃.

[0062] Comparative Example 2

[0063] This comparative example provides a glass fiber reinforced polypropylene material, which is implemented in the same manner as in Example 1, except that UHMW-PE is replaced with an equal part by weight of high-density polyethylene. All other raw material compositions and preparation processes are the same as in Example 1.

[0064] Its 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 mixed evenly according to weight parts and then fed into a twin-screw extruder through the main feed port. At the same time, glass fiber is added through the glass fiber port. After melt extrusion, anti-warping glass fiber reinforced polypropylene material is obtained. The main speed of the twin-screw extruder is 430 rpm, and the temperature from the feeding section to the die head is 220℃, 220℃, 220℃, 220℃, 230℃, 230℃, 230℃, 210℃, 210℃, 210℃.

[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, and 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 tested according to ISO 527, and the tensile speed is 5 mm / min.

[0074] (2) Bending strength and bending modulus are tested according to ISO 178, with a bending speed of 2 mm / min.

[0075] (3) The impact strength of the cantilever beam notch is tested according to the test standard ISO 180. The test conditions are: 23℃, molded notch, type 1A molding.

[0076] (4) Shrinkage rate was measured after the square plate with injection molded dimensions of 60×60×2mm was stored at 23℃ for 48 hours. Shrinkage rate = (molded size - sample size) / molded size, shrinkage rate difference = shrinkage rate perpendicular to the flow direction - shrinkage rate in the flow direction. Warpage was visually observed in the square plate above, and the results were evaluated.

[0077] As can be seen from the test results in Table 1, the glass fiber reinforced polypropylene material of this invention has a lower difference in transverse and longitudinal shrinkage rates compared with traditional glass fiber reinforced polypropylene materials, which can significantly improve the warping of the parts.

[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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 embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A glass fiber reinforced polypropylene material for improving warpage after injection molding, characterized in that, It is prepared from 47-84.5 parts polypropylene, 10-40 parts glass fiber, 2-6 parts maleic anhydride grafted polypropylene, 3-6 parts ultra-high molecular weight polyethylene, 0.2-0.5 parts antioxidant and 0.3-0.5 parts light stabilizer in parts by weight. Wherein, the polypropylene is any one of PP T30S, PP YPJ1215C or PP Z30S, and the ultra-high molecular weight polyethylene is any one of GUR 5113 or L5000.

2. The glass fiber reinforced polypropylene material as described in claim 1, characterized in that, The glass fiber is chopped glass fiber.

3. The glass fiber reinforced polypropylene material as described in claim 2, characterized in that, The chopped glass has a fiber length of 3-25 mm and a fiber diameter of 9-13 μm.

4. The glass fiber reinforced polypropylene material as described in claim 1, characterized in that, In the maleic anhydride-grafted polypropylene, the grafting rate of maleic anhydride is 0.5~3wt%.

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

6. The glass fiber reinforced polypropylene material as described in claim 1, characterized in that, The light stabilizer is a hindered amine light stabilizer.

7. A method for preparing a glass fiber reinforced polypropylene material as described in any one of claims 1-6, characterized in that, Includes the following steps: Mix 47-84.5 parts polypropylene, 2-6 parts maleic anhydride-grafted polypropylene, 3-6 parts ultra-high molecular weight polyethylene, 0.2-0.5 parts antioxidant and 0.3-0.5 parts light stabilizer evenly according to the weight ratio to obtain the mixture. The mixture is added to the main feed port of a twin-screw extruder, and 10-40 parts of glass fiber are added to the glass fiber inlet. After melt extrusion, granulation and drying, anti-warping glass fiber reinforced polypropylene material is obtained.

8. The preparation method according to claim 7, characterized in that, The twin-screw extruder operates at a speed of 300-600 rpm and has a barrel temperature of 200-250°C.

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