Low-warpage low-creep reinforced polypropylene composite material and preparation method thereof

Abstract

The invention discloses a low-warpage low-creep reinforced polypropylene composite material and a preparation method thereof. The high-melt-strength polypropylene composite material is prepared from the following components in parts by weight: 65-75 parts of low-melt-index high-melt-strength polypropylene, 20-30 parts of glass flake filler, 3 parts of compatilizer, 0.5 part of carbon black powder and 2 parts of other functional aids. According to the prepared product, the overall deformation quantity of the product after injection molding is reduced through long-chain branching and cross-linking of the base material and the space size effect of the filler, meanwhile, the creep property is extremely high, the product can be widely applied to plastic structural parts with the mechanical property requirement, and the industrial production and the industrial production are facilitated. A brand-new material solution is provided for aerospace.

Description

Technical Field

[0005] The present invention belongs to the technical field of polymer composite materials, in particular to a low-warpage, low-creep reinforced polypropylene composite material and a preparation method thereof. The material is suitable for the automotive industry, industrial production, and aerospace fields. Technical Background

[0006] As a lightweight, cost-effective thermoplastic, polypropylene plays an important role in many industrial fields such as automobiles, home appliances, and packaging. With the improvement of environmental awareness and the pursuit of sustainable development, the development of concepts such as replacing steel with plastic and plastic with plastic, the enhancement and modification of polypropylene materials has become an effective way to reduce costs and carbon emissions. Traditional modification channels generally enhance polypropylene by adding glass fillers such as long glass fiber, short glass fiber, and glass microbeads. The mechanical properties of polypropylene have been significantly improved, enabling it to replace traditional engineering plastics such as ABS and PC to a certain extent, thereby achieving cost reduction and environmental protection while ensuring product performance.

[0007] However, traditional reinforced polypropylene materials often face the problem of warping and deformation during the injection molding process, which not only affects the appearance and precision of the product, but also may lead to a decrease in material performance and increase the risk during use. At the same time, the creep performance of the polypropylene material itself is insufficient, and it is easy to deform under the subsequent long-term use conditions. After the parts are warped, this deformation will continue to intensify, seriously affecting the service life of the parts. From a microscopic perspective, the reinforced material is mainly composed of two parts. The creep performance of conventional homopolymer polypropylene is not outstanding, and it is greatly affected by temperature. It is not conducive to maintaining the original size of the material after injection molding. At the same time, another major factor in the warping of the material is that in the traditional glass fiber reinforcement system, the glass fiber has a certain aspect ratio, and the different aspect ratio distributions in different directions cause the material to have a certain directionality during the recrystallization process. This uncontrollable and uneven direction has always been a problem that plagues the application of reinforced polypropylene. Without changing the existing molds and production lines, extending the service life of parts by optimizing the reinforced polypropylene itself, reducing the deformation of parts and improving reliability are important directions for reducing carbon emissions and improving efficiency in industrial production. Summary of the invention

[0008] The purpose of the present invention is to provide a low-warpage and low-creep reinforced polypropylene composite material and a preparation method thereof, so as to solve the problems of low warpage deformation and creep performance of the reinforced polypropylene material in the prior art during use.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A low-warpage, low-creep reinforced polypropylene composite material, comprising the following components in parts by weight:

[0011]

[0012] The low melt index high melt strength polypropylene (HMSPP) has an MFR ≤ 2 and a tensile yield stress ≥ 25 (GB / T1040.22022)

[0013] The glass flake filler has a thickness of ≤1 μm and a particle size of 1 to 2000 μm.

[0014] The compatibilizer is a maleic anhydride grafted polypropylene compound, with a melt index of 25-50 g / 10 min and a grafting rate of 0.5-1.5%.

[0015] The toner is prepared by furnace method with a specific surface area of ​​120-145m 2 / g.

[0016] The functional additives include one or a combination of antioxidants 1010, 1035, 1075, 168, 618, 619F, DSTP, DLTP, 412S, hindered ammonium light stabilizers GW622, GW944, and UV5229.

[0017] The method for preparing the low-warpage and low-creep reinforced polypropylene composite material comprises the following steps:

[0018] (1) Mix polypropylene, compatibilizer, functional additive and color powder in proportion and stir at high speed.

[0019] (2) After the materials in step (1) are mixed evenly, they are fed into a twin-screw extruder with a processing temperature of 200-240°C and a main engine speed of 400-600rpm. The glass flake filler is easily damaged by shear during dispersion, and the base material has a low melt index and is not easy to disperse. A two-step method is used to add the filler. 10% of the glass flake filler is added to the first side feed port located in the first three sections. A vacuum exhaust system is added during the stirring process, and the remaining filler is added to the second side feed port located in the last three sections for stirring.

[0020] (3) The temperature of the segmented extrusion device is respectively 200°C for the front section, 220°C for the middle section, and 230°C for the rear section, and then cooled in a water tank and pelletized by a pelletizer to prepare reinforced polypropylene pellets with a length of 2-4 mm and an ash content of 20-30%.

[0021] The present invention uses nano glass microflakes as filler materials through the design of material formula system, and successfully prepares a reinforced polypropylene material with low creep and anti-warping properties. The base polypropylene adopts low melt index high melt strength polypropylene (HMSPP), which has long chain branching cross-linking that conventional PP does not have, and improves the melt strength and creep performance through the cross-linking of various long chain branches on the main chain. The microflakes used as fillers have a high diameter-thickness ratio. Unlike traditional glass fiber reinforcement, the structure of glass flakes tends to be distributed in parallel throughout the polypropylene system, effectively reducing the problem of anisotropic distribution, thereby solving the problem of material warping from the perspective of material microstructure. Furthermore, polypropylene with a high melt long chain branching system and glass flakes with a large specific surface area are easily formed under the guidance of the graft, so that the creep performance of the material is greatly improved. After injection molding, the deformation of the material is significantly reduced, effectively reducing the risk of warping, which means that its stability and durability in practical applications are enhanced. For injection molding manufacturing companies, the cost of mold design and part maintenance is reduced, and carbon reduction and efficiency improvement are effectively achieved.

[0022] The advantages of the low-warpage, low-creep reinforced polypropylene composite material of the present invention are that it utilizes the characteristics of large specific surface area and controllable spatial distribution of glass flakes to achieve micro-crosslinking and controllable spatial anisotropy of fillers and polypropylene, thereby improving the warpage problem of the reinforced material and improving the creep performance, greatly improving the reliability of subsequent use. The method is simple in steps and can be promoted industrially, the material deformation is significantly reduced, and it has extremely high commercial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a strain rate comparison chart of Example 1-2 and Comparative Example 1-3. DETAILED DESCRIPTION

[0024] The following is a further explanation of the present invention in conjunction with the embodiments, but the embodiments do not limit the present invention in any form. The raw materials used are as follows:

[0025] Polypropylene Zhenhai Petrochemical PP E02ES Sinopec K8003

[0026] Glass flake filling Japan NGS FINEFLAKA REFG-315

[0027] Grafted Huawen HW501

[0028] Antioxidant SI Group Chemical (Shanghai) Co., Ltd. 1010168DSTP

[0029] Carbon black powder industrial grade commercially available

[0030] Chopped fiberglass Chongqing International 305H

[0031] Glass micro beads Sanlight HM10

[0032] Embodiment 1:

[0033] (1) Mix polypropylene E02ES, compatibilizer, functional additive and color powder in proportion and stir at high speed.

[0034] (2) After the materials in step (1) are mixed evenly, they are fed into a twin-screw extruder at a processing temperature of 200-240°C and a main engine speed of 400 rpm. 10% of glass flake filler is added to the first side feed port located in the first three sections. A vacuum exhaust system is added during the stirring process, and the remaining filler is added to the second side feed port located in the last three sections for stirring.

[0035] (3) The temperature of the segmented extrusion device is 200℃ for the front section, 220℃ for the middle section, and 240℃ for the rear section. The product is then cooled in a water tank and pelletized by a pelletizer to produce reinforced polypropylene pellets with a length of 2-4 mm and an ash content of 20%.

[0036] Embodiment 2:

[0037] (1) Mix polypropylene E02ES, compatibilizer, functional additive and color powder in proportion and stir at high speed.

[0038] (2) After the materials in step (1) are mixed evenly, they are fed into a twin-screw extruder with a processing temperature of 200-240°C and a main engine speed of 400 rpm. 15% of glass flake filler is added to the first side feed port located in the first three sections. A vacuum exhaust system is added during the stirring process, and the remaining filler is added to the second side feed port located in the last three sections for stirring.

[0039] (3) The segmented extrusion device is respectively 200°C for the front section, 220°C for the middle section, and 230°C for the rear section, and then cooled in a water tank and pelletized by a pelletizer to prepare reinforced polypropylene pellets with a length of 2-4 mm and an ash content of 30%.

[0040] Comparative Example 1:

[0041] (1) Mix polypropylene E02ES, compatibilizer, functional additive and color powder in proportion and stir at high speed.

[0042] (2) The materials in step (1) are mixed evenly and then fed into a twin-screw extruder. The processing temperature is 200-240°C and the main engine speed is 400 rpm. Ordinary chopped glass fiber Chongqing International Brand 305H is used as a comparison. 10% of the chopped glass fiber is added to the first side feed port located in the first three sections. A vacuum exhaust system is added during the stirring process. The remaining filler is added to the second side feed port located in the last three sections for stirring.

[0043] (3) The temperature of the segmented extrusion device is 200℃ for the front section, 220℃ for the middle section, and 240℃ for the rear section. The product is then cooled in a water tank and pelletized by a pelletizer to produce reinforced polypropylene pellets with a length of 2-4 mm and an ash content of 20%.

[0044] Comparative Example 2:

[0045] (1) Mix polypropylene E02ES, compatibilizer, functional additive and color powder in proportion and stir at high speed.

[0046] (2) After the materials in step (1) are mixed evenly, they are fed into a twin-screw extruder. The processing temperature is 200-240°C and the main engine speed is 400 rpm. Glass microspheres HM10 are used as a comparison. 10% of glass microspheres are added to the first side feed port located in the first three sections. A vacuum exhaust system is added during the stirring process. The remaining filler is added to the second side feed port located in the last three sections for stirring.

[0047] (3) The temperature of the segmented extrusion device is 200℃ for the front section, 220℃ for the middle section, and 240℃ for the rear section. The product is then cooled in a water tank and pelletized by a pelletizer to produce reinforced polypropylene pellets with a length of 2-4 mm and an ash content of 20%.

[0048] Comparative Example 3:

[0049] (1) Mix polypropylene K8003, compatibilizer, functional additive and color powder in proportion and stir at high speed.

[0050] 2) After the materials in step (1) are mixed evenly, they are fed into a twin-screw extruder at a processing temperature of 200-240°C and a main engine speed of 400 rpm. 10% of glass flake filler is added to the first side feed port located in the first three sections. A vacuum exhaust system is added during the stirring process, and the remaining filler is added to the second side feed port located in the last three sections for stirring.

[0051] (3) The segmented extrusion device is respectively 200°C for the front section, 220°C for the middle section, and 230°C for the rear section, and then cooled in a water tank and pelletized by a pelletizer to prepare reinforced polypropylene pellets with a length of 2-4 mm and an ash content of 20%.

[0052] The composition and mass percentage of the ingredients in the comparative examples and embodiments of the present invention are shown in Table 1 below.

[0053] Table 1: Weight content of the embodiments and comparative examples

[0054]

[0055] The mechanical properties of the above particles were tested, and the warpage and creep properties of the samples after injection molding were tested.

[0056] 1. Direct injection molding sample testing, using conventional mechanical properties testing, the results are as follows:

[0057] Table 2 Direct injection molding performance test results of embodiments and comparative examples

[0058]

[0059] 2. After injection molding into flame-retardant samples, the warpage degree test is carried out. The material is injection molded into a 300*100*3mm flame-retardant sample and then left to stand for 48 hours. A heavy object is used to press down one corner of the square plate on a plane, and then the warpage heights of the other three corners are tested. The maximum value is taken as the warpage degree. Five square plates are tested each time and the average value is taken. The larger the value, the more serious the warpage. The test results are as follows:

[0060] Table 3 Comparison of direct injection molding warpage performance between examples and comparative examples

[0061] Warpage(cm) 1 2 3 4 5 Mean Example 1 2.7 2.7 2.5 2.6 2.5 2.60 Example 2 3.3 3.4 3.5 3.3 3.2 3.34 Comparative Example 1 3.8 3.7 3.7 4.0 3.7 3.78 Comparative Example 2 2.6 2.4 2.3 2.2 2.4 2.38 Comparative Example 3 2.5 2.7 2.4 2.6 2.7 2.58

[0062] 3. Creep performance test: creep test was performed on the injection molded specimens of the embodiment and the comparative example according to ISO 899-1 standard. The test temperature was 23°C, and the strain rate was taken for 100h for comparison. The results Figure 1 As shown:

[0063] By comparing the test results of the embodiments and comparative examples (1)(2)(3), it can be found that the mechanical properties of the HMSPP material filled with glass flakes are lower than those of the traditional material with short glass fibers, but it has obvious advantages over the material filled with glass beads. Compared with conventional PP, the performance difference is not much after using HMSPP as the base material. From the perspective of warping, after using glass flakes for filling, the warping is greatly improved compared with the traditional short fiber reinforced material. The warping is reduced by 30% with the same filling amount, which is close to the glass bead filling system. By comparing the creep properties of different base materials with the same filling amount, it can be seen that the creep performance of the material using HMSPP is more than 40% lower in strain rate than that of ordinary PP materials in the 100h test, and the deformation is greatly reduced, indicating that the risk of deformation of the material is greatly reduced under long-term use, which is helpful for subsequent long-term use conditions.

[0064] The invention can be applied to many industries such as the automotive industry, aerospace, etc., and can effectively reduce subsequent processing steps, and provide assistance for production cost reduction, energy conservation and emission reduction. The above-mentioned embodiments are only descriptions of the preferred implementation methods of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A low warpage and low creep reinforced polypropylene composite material, characterized in that: In parts by weight, it comprises the following components:

2. The low warpage and low creep reinforced polypropylene composite material according to claim 1, characterized in that: The low melt index high melt strength polypropylene (HMSPP) has an MFR of ≤2 and a tensile yield stress of ≥25.

3. The low warpage and low creep reinforced polypropylene composite material according to claim 1, characterized in that: The glass flake filler has a thickness of ≤1 μm and a particle size of 1 to 2000 μm.

4. The low warpage and low creep reinforced polypropylene composite material according to claim 1, characterized in that: The compatibilizer is a maleic anhydride grafted polypropylene compound with a melt index of 25-50 g / 10 min and a grafting rate of 0.5-1.5%.

5. The low warpage and low creep reinforced polypropylene composite material according to claim 1, characterized in that: The toner is prepared by furnace method with a specific surface area of ​​120-145m 2 / g.

6. The low warpage and low creep reinforced polypropylene composite material according to claim 1, characterized in that: The functional additives include one or a combination of antioxidants 1010, 1035, 1075, 168, 618, 619F, DSTP, DLTP, 412S, hindered ammonium light stabilizers GW622, GW944, and UV5229.

7. The method for preparing a low-warpage, low-creep reinforced polypropylene composite material according to claim 1, characterized in that: The following steps are involved: (1) Mixing polypropylene, compatibilizer, functional additive and color powder in proportion and stirring at high speed; (2) After the materials in step (1) are mixed evenly, they are fed into a twin-screw extruder. The processing temperature is 200-240°C and the main engine speed is 400-600rpm. The glass flake filler is easily damaged by shear during the dispersion process. At the same time, the base material has a low melt index and is not easy to disperse. The filler is added in a two-step method. 10% of the glass flake filler is added to the first side feed port located in the first three sections. A vacuum exhaust system is added during the stirring process. The remaining filler is added to the second side feed port located in the last three sections for stirring. (3) The temperature of the segmented extrusion device is respectively 200°C for the front section, 220°C for the middle section, and 230°C for the rear section, and then cooled in a water tank and pelletized by a pelletizer to prepare reinforced polypropylene pellets with a length of 2-4 mm and an ash content of 20-30%.

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