Glass fiber reinforced polypropylene material and preparation method thereof

Abstract

The invention provides a glass fiber reinforced polypropylene material and a preparation method thereof, and belongs to the technical field of propylene copolymers. The preparation method comprises the steps of maleic anhydride copolymer preparation, polypropylene pretreatment, glass fiber pretreatment and blending. The method for preparing the maleic anhydride copolymer comprises the following steps: adding maleic anhydride, styrene and azodiisobutyronitrile into methylbenzene, heating to 70-90 DEG C in a nitrogen environment, stirring and reacting for 1-2 hours at the current temperature, adding glycidyl acrylate, continuously reacting for 30-50 minutes, naturally cooling, filtering, washing and drying to obtain the maleic anhydride copolymer. According to the glass fiber reinforced polypropylene material, the tensile strength is 32-35 MPa, the elongation at break is 71-75%, and after a thermal aging test, the tensile strength is 29-33 MPa, and the elongation at break is 65-70%.

Description

Technical Field

[0001] This invention belongs to the field of propylene copolymer technology, specifically relating to a glass fiber reinforced polypropylene material and its preparation method. Background Technology

[0002] Polypropylene has advantages such as low density, good chemical resistance, good heat resistance, excellent electrical insulation, good processing performance, relatively low price, and recyclability, and is widely used in packaging, automobiles, construction, and medical fields. However, single polypropylene still cannot meet the actual application needs of the market, and it needs to be modified by toughening and strengthening. After being reinforced with glass fiber, polypropylene has made a qualitative leap in terms of mechanical properties, heat resistance, and dimensional stability.

[0003] However, the technology of glass fiber reinforced polypropylene materials still faces multiple bottlenecks: 1. The large difference in polarity between glass fiber and polypropylene leads to insufficient interfacial compatibility, causing glass fiber agglomeration and low stress transfer efficiency; 2. The interfacial bonding sites between glass fiber and polypropylene become preferential sites for oxidative degradation, increasing the aging rate by 2 to 3 times.

[0004] Maleic anhydride-grafted polypropylene is the most commonly used reactive compatibilizer in polypropylene-based composites. Its molecular backbone consists of non-polar polypropylene segments with polar maleic anhydride groups grafted onto its side chains. It can simultaneously achieve compatibility with polypropylene and interfacial reaction with polar fillers / fibers (such as glass fibers), making it a core material for solving the problem of poor interfacial compatibility between polypropylene and polar components.

[0005] However, 1. Maleic anhydride has a low grafting rate with polypropylene and glass fiber, resulting in fewer interfacial reaction sites and limited reinforcement effect. If the amount of initiator or the concentration of maleic anhydride is increased to improve the grafting rate, it is easy to induce the self-polymerization of maleic anhydride (uneven chain segment distribution, affecting material properties) and the cross-linking reaction of polypropylene molecular chains (increased melt viscosity, decreased fluidity, and processing difficulties); 2. Maleic anhydride has a low heat resistance temperature, which overlaps with the processing temperature of polypropylene. During processing, maleic anhydride is prone to decomposition, producing small molecule volatiles, resulting in bubbles and a strong odor in the product, while also reducing grafting efficiency; 3. The interfacial bonding between maleic anhydride-grafted polypropylene and glass fiber is an ester bond. In a humid and hot environment, the ester bond is prone to hydrolysis, leading to interfacial debonding and a decrease in mechanical properties. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a glass fiber reinforced polypropylene material and its preparation method, achieving the following objectives: to provide a glass fiber reinforced polypropylene material that improves the interfacial compatibility between glass fiber and polypropylene and enhances aging resistance.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing a glass fiber reinforced polypropylene material includes: 1. Preparation of maleic anhydride copolymer Maleic anhydride, styrene, azobisisobutyronitrile (AIBN) were added to toluene. The mixture was heated to 70–90°C under nitrogen atmosphere. After stirring for 1–2 hours at the current temperature, glycidyl acrylate was added and the reaction was continued for 30–50 minutes. After natural cooling, the mixture was filtered and washed. The filter cake was dried to constant weight in a vacuum drying oven to obtain the maleic anhydride copolymer. The mass ratio of maleic anhydride, styrene, azobisisobutyronitrile, toluene, and glycidyl acrylate is 280–300: 14.9–15.3: 6–8: 310–330: 20.3–20.5. The stirring rate is 50–60 r / min; The drying temperature is 55–60°C; The degree of polymerization of the maleic anhydride copolymer is 1000-2000.

[0008] 2. Polypropylene pretreatment Polypropylene is crushed into granules of 2-4 mm, cleaned and dried, and then placed in an ozone generator for 30-50 minutes to obtain pretreated polypropylene. The ozone generator has an ozone concentration of 300–500 mg / m³, a processing temperature of 50–60°C, and a relative humidity of 40–50%.

[0009] 3. Glass fiber pretreatment Glass fibers were added to anhydrous ethanol, then KH550 was added dropwise. After ultrasonic dispersion for 45-50 min, the solid product was centrifuged, washed clean, and dried at 90-100℃ for 6-8 h to obtain pretreated glass fibers. The mass ratio of glass fiber, anhydrous ethanol, and KH550 is 0.2–0.3:120–140:0.01–0.03. The ultrasonic power is 400-500W; The centrifugation rate is 1000–2000 r / min.

[0010] 4. Blending After the pretreated polypropylene, pretreated glass fiber, and maleic anhydride copolymer are mixed evenly, the mixture is added to a twin-screw extruder. The temperature of the twin-screw extruder is set to 180-200℃, the speed is 200-300 r / min, and the residence time of the mixture in the twin-screw extruder is 1-3 min. After extrusion, the mixture is cooled to obtain glass fiber reinforced polypropylene material.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Maleic anhydride copolymer: Maleic anhydride and styrene are copolymerized. S1. The benzene ring of styrene exhibits a conjugation effect, resulting in a high electron cloud density in its double bonds. When copolymerized with maleic anhydride, styrene preferentially reacts with free radicals to form stable styrene free radical intermediates, thus reducing the probability of maleic anhydride self-polymerization. Furthermore, the aromatic ring structure of styrene can inhibit the cross-linking of polypropylene molecular chains, achieving a balance between high grafting rate and low melt viscosity. S2. The addition of glycidyl acrylate end-capping changes the carboxyl groups at both ends of the maleic anhydride copolymer to epoxy groups. These epoxy groups can undergo ring-opening reactions with the hydroxyl groups on the glass fiber surface, forming ether bonds that are more stable than ester bonds. S3. By controlling specific reaction conditions, maleic anhydride copolymers with a degree of polymerization of 1000–2000 are obtained. Simultaneously with grafting onto polypropylene, the double chains intertwine, constructing a dual interfacial bond, significantly improving interfacial stability under humid and hot conditions. S4. Compared to maleic anhydride, the maleic anhydride copolymer exhibits higher thermal stability and is less prone to decomposition at the processing temperature of polypropylene.

[0012] 2. Pretreatment of polypropylene and glass fiber increases the number of bonding sites on polypropylene and glass fiber.

[0013] 3. The glass fiber reinforced polypropylene material of the present invention has a tensile strength of 32-35 MPa and an elongation at break of 71-75%. After heat aging test, the tensile strength is 29-33 MPa and the elongation at break is 65-70%. Detailed Implementation

[0014] Example 1 1. Preparation of maleic anhydride copolymer Maleic anhydride, styrene, azobisisobutyronitrile (AIBN) were added to toluene. The mixture was heated to 80°C under nitrogen atmosphere. After stirring for 1.5 hours at the current temperature, glycidyl acrylate was added, and the reaction was continued for 40 minutes. After natural cooling, the mixture was filtered and washed. The filter cake was dried to constant weight in a vacuum drying oven to obtain the maleic anhydride copolymer. The mass ratio of maleic anhydride, styrene, azobisisobutyronitrile, toluene, and glycidyl acrylate is 290:15.1:7:320:20.4. The stirring rate is 55 r / min; The drying temperature is 57°C; The degree of polymerization of the maleic anhydride copolymer is 1400 to 1700.

[0015] 2. Polypropylene pretreatment Polypropylene was crushed into 3mm granules, cleaned and dried, and then placed in an ozone generator for 40 minutes to obtain pretreated polypropylene. The ozone generator has an ozone concentration of 400 mg / m³, a processing temperature of 55°C, and a relative humidity of 45%.

[0016] 3. Glass fiber pretreatment Glass fibers were added to anhydrous ethanol, then KH550 was added dropwise, and the mixture was ultrasonically dispersed for 47 min. After centrifugation, the solid product was cleaned and dried at 95℃ for 7 h to obtain pretreated glass fibers. The mass ratio of the glass fiber, anhydrous ethanol, and KH550 is 0.25:130:0.02. The ultrasonic power is 450W; The centrifugation rate is 1500 r / min.

[0017] 4. Blending After the pretreated polypropylene, pretreated glass fiber, and maleic anhydride copolymer are mixed evenly, the mixture is added to a twin-screw extruder. The twin-screw extruder temperature is set to 190℃, the speed is 250r / min, and the residence time of the mixture in the twin-screw extruder is 2min. After extrusion, the mixture is cooled to obtain glass fiber reinforced polypropylene material.

[0018] Example 2 1. Preparation of maleic anhydride copolymer Maleic anhydride, styrene, azobisisobutyronitrile (AIBN) were added to toluene. The mixture was heated to 70°C under nitrogen atmosphere. After stirring for 1 hour at the current temperature, glycidyl acrylate was added and the reaction was continued for 30 minutes. After natural cooling, the mixture was filtered and washed. The filter cake was dried to constant weight in a vacuum drying oven to obtain the maleic anhydride copolymer. The mass ratio of maleic anhydride, styrene, azobisisobutyronitrile, toluene, and glycidyl acrylate is 280:14.9:6:310:20.3. The stirring rate is 50 r / min; The drying temperature is 55°C; The degree of polymerization of the maleic anhydride copolymer is 1000-1400.

[0019] 2. Polypropylene pretreatment Polypropylene was crushed into 2mm granules, cleaned and dried, and then placed in an ozone generator for 30 minutes to obtain pretreated polypropylene. The ozone generator has an ozone concentration of 300 mg / m³, a processing temperature of 50℃, and a relative humidity of 40%.

[0020] 3. Glass fiber pretreatment Glass fibers were added to anhydrous ethanol, then KH550 was added dropwise, and the mixture was ultrasonically dispersed for 45 min. After centrifugation, the solid product was cleaned and dried at 90℃ for 6 h to obtain pretreated glass fibers. The mass ratio of the glass fiber, anhydrous ethanol, and KH550 is 0.2:120:0.01. The ultrasonic power is 400W; The centrifugation rate is 1000 r / min.

[0021] 4. Blending After the pretreated polypropylene, pretreated glass fiber, and maleic anhydride copolymer are mixed evenly, the mixture is added to a twin-screw extruder. The twin-screw extruder temperature is set to 180℃, the speed is 200r / min, and the residence time of the mixture in the twin-screw extruder is 1min. After extrusion, the mixture is cooled to obtain glass fiber reinforced polypropylene material.

[0022] Example 3 1. Preparation of maleic anhydride copolymer Maleic anhydride, styrene, azobisisobutyronitrile (AIBN) were added to toluene. The mixture was heated to 90°C under nitrogen atmosphere. After stirring for 2 hours at the current temperature, glycidyl acrylate was added and the reaction was continued for 50 minutes. After natural cooling, the mixture was filtered and washed. The filter cake was dried to constant weight in a vacuum drying oven to obtain the maleic anhydride copolymer. The mass ratio of maleic anhydride, styrene, azobisisobutyronitrile, toluene, and glycidyl acrylate is 300:15.3:8:330:20.5. The stirring rate is 60 r / min; The drying temperature is 60°C; The degree of polymerization of the maleic anhydride copolymer is 1700–2000.

[0023] 2. Polypropylene pretreatment Polypropylene was crushed into 4mm granules, cleaned and dried, and then placed in an ozone generator for 50 minutes to obtain pretreated polypropylene. The ozone generator has an ozone concentration of 500 mg / m³, a processing temperature of 60°C, and a relative humidity of 50%.

[0024] 3. Glass fiber pretreatment Glass fibers were added to anhydrous ethanol, then KH550 was added dropwise, ultrasonically dispersed for 50 min, centrifuged, the solid product was cleaned, and dried at 100℃ for 8 h to obtain pretreated glass fibers. The mass ratio of the glass fiber, anhydrous ethanol, and KH550 is 0.3:140:0.03. The ultrasonic power is 500W; The centrifugation rate is 2000 r / min.

[0025] 4. Blending After the pretreated polypropylene, pretreated glass fiber, and maleic anhydride copolymer are mixed evenly, the mixture is added to a twin-screw extruder. The twin-screw extruder temperature is set to 200℃, the speed is 300r / min, and the residence time of the mixture in the twin-screw extruder is 3min. After extrusion, the mixture is cooled to obtain glass fiber reinforced polypropylene material.

[0026] Comparative Example 1 Based on Example 1, the step of preparing maleic anhydride copolymer in step 1 is omitted, and maleic anhydride of equal mass is used instead in step 4. The remaining steps are the same.

[0027] Comparative Example 2 Based on Example 1, the polypropylene pretreatment step in step 2 is omitted, and an equal mass of polypropylene is used as a substitute in step 4. The remaining steps are the same.

[0028] Test case 1. The glass fiber reinforced polypropylene materials prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to the following data tests. The test results are shown in Table 1: Table 1

[0029] Note: The method for the heat aging test is to place the glass fiber reinforced polypropylene material in a heat aging chamber and age it at 120°C for 10 hours.

[0030] As shown in Table 1, the test results show that in Comparative Example 1, maleic anhydride was used instead of maleic anhydride copolymer. Compared with maleic anhydride copolymer, maleic anhydride has poor thermal stability and low grafting efficiency, which leads to a decrease in tensile strength and elongation at break, as well as a decrease in aging resistance. Comparative Example 2 uses polypropylene instead of pretreated polypropylene. Compared with pretreated polypropylene, polypropylene has fewer grafting sites, which leads to a decrease in the grafting rate with maleic anhydride copolymer and a poor bonding effect with glass fiber, resulting in a decrease in tensile strength and elongation at break, as well as a decrease in aging resistance.

Claims

1. A method for preparing a glass fiber reinforced polypropylene material, characterized in that: The preparation method includes preparing maleic anhydride copolymer, pretreating polypropylene, pretreating glass fiber, and blending. The method for preparing maleic anhydride copolymer is as follows: maleic anhydride, styrene, azobisisobutyronitrile (AIBN) are added to toluene, heated to 70-90°C under nitrogen atmosphere, and then stirred for 1-2 hours at the current temperature. Glycidyl acrylate is then added, and the reaction continues for 30-50 minutes. After natural cooling, the mixture is filtered and washed, and the filter cake is dried to constant weight in a vacuum drying oven to obtain maleic anhydride copolymer.

2. The method for preparing a glass fiber reinforced polypropylene material according to claim 1, characterized in that: In the method for preparing maleic anhydride copolymer, the mass ratio of maleic anhydride, styrene, azobisisobutyronitrile, toluene, and glycidyl acrylate is 280–300: 14.9–15.3: 6–8: 310–330: 20.3–20.

5. The stirring rate is 50–60 r / min; The drying temperature is 55–60℃; The degree of polymerization of maleic anhydride copolymers is 1000–2000.

3. The method for preparing a glass fiber reinforced polypropylene material according to claim 1, characterized in that: The method for pretreating polypropylene is as follows: polypropylene is crushed into granules of 2-4 mm, cleaned and dried, and then placed in an ozone generator for 30-50 minutes to obtain pretreated polypropylene.

4. The method for preparing a glass fiber reinforced polypropylene material according to claim 3, characterized in that: In the polypropylene pretreatment method, an ozone generator is used, the ozone concentration is 300-500 mg / m³, the treatment temperature is 50-60℃, and the relative humidity is 40-50%.

5. The method for preparing a glass fiber reinforced polypropylene material according to claim 1, characterized in that: The method for pretreating glass fibers is as follows: glass fibers are added to anhydrous ethanol, then KH550 is added dropwise, ultrasonically dispersed for 45-50 minutes, centrifuged, the solid product is cleaned, and dried at 90-100℃ for 6-8 hours to obtain pretreated glass fibers.

6. The method for preparing a glass fiber reinforced polypropylene material according to claim 5, characterized in that: In the glass fiber pretreatment method, the mass ratio of glass fiber, anhydrous ethanol, and KH550 is 0.2-0.3:120-140:0.01-0.

03. The ultrasonic power is 400–500W; The centrifugation rate is 1000–2000 r / min.

7. The method for preparing a glass fiber reinforced polypropylene material according to claim 1, characterized in that: The blending method involves uniformly mixing pretreated polypropylene, pretreated glass fiber, and maleic anhydride copolymer, then adding the mixture to a twin-screw extruder. The twin-screw extruder temperature is set to 180–200°C, the rotation speed to 200–300 r / min, and the residence time of the mixture in the twin-screw extruder is 1–3 min. After extrusion, the mixture is cooled to obtain glass fiber reinforced polypropylene material.

8. A glass fiber reinforced polypropylene material prepared by the preparation method according to any one of claims 1-7.

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