PP / PA composite material for commercial-grade electric rice cooker middle frame and preparation method thereof

Abstract

The application relates to the field of composite materials and preparation thereof, and particularly discloses a PP / PA composite material for a commercial-grade electric rice cooker middle frame and a preparation method thereof.A PP / PA composite material for a commercial-grade electric rice cooker middle frame comprises the following raw materials in parts by mass: 20-30 parts of polypropylene, 35-41 parts of polyamide, 10-15 parts of high-aspect-ratio talcum powder, 5-10 parts of short-cut glass fiber, 2.5-5 parts of a compatilizer, 0.3 parts of a lubricant, 0.6 parts of an antioxidant system, and 2 parts of black masterbatch; in addition, the composite material prepared by the application has the advantages of high polypropylene-polyamide composite material temperature resistance.

Description

Technical Field

[0001] This application relates to the field of composite materials and their preparation, and more specifically, it relates to a PP / PA composite material for the inner frame of a commercial rice cooker and its preparation method. Background Technology

[0002] The rice cooker industry has developed rapidly in recent years, but it is currently mainly concentrated in the household sector. With the improvement of living standards and the growth of commercial demand, the commercial rice cooker market is gradually emerging. Household rice cookers have relatively lower usage scenarios and performance requirements, and conventional filled polypropylene materials can meet their needs for temperature resistance and deformation resistance. These materials are low in cost and easy to process, which has enabled the widespread adoption of household rice cookers, providing a convenient cooking method for family members.

[0003] There are several traditional approaches to material selection for commercial rice cookers. A common method is to use polypropylene, the same material used in household rice cookers, which has performed well in home settings and has therefore been tested in commercial rice cookers. Other options include ABS, PC, PA6, and PBT. These materials have a proven track record in other industrial sectors and are considered to possess performance characteristics suitable for the requirements of commercial rice cookers.

[0004] However, existing materials for commercial rice cookers have significant drawbacks. Due to the high power and long operating time of commercial rice cookers, materials need to possess higher temperature resistance and deformation resistance, while also meeting stringent requirements such as good surface finish, adaptability to high temperature and humidity environments, low deformation, low cost, and food-grade properties. Polypropylene used in household rice cookers lacks sufficient temperature resistance, while other materials such as ABS also have poor temperature resistance. PC contains bisphenol A monomers, making it difficult to meet food-grade standards, and PA6 and PBT also suffer from dimensional instability and easy deformation, all of which fail to meet the practical application requirements of commercial rice cookers. Summary of the Invention

[0005] To improve the temperature resistance of polypropylene-polyamide composite materials, this application provides a commercial-grade PP / PA composite material for the inner frame of a rice cooker and its preparation method.

[0006] In a first aspect, this application provides a PP / PA composite material for the middle frame of a commercial-grade rice cooker, employing the following technical solution: A commercial-grade PP / PA composite material for the inner frame of a rice cooker comprises the following raw materials in parts by weight: 20-30 parts polypropylene, 35-41 parts polyamide, 10-15 parts high aspect ratio talc, 5-10 parts chopped glass fiber, 2.5-5 parts compatibilizer, 0.3 parts lubricant, 0.6 parts antioxidant system, and 2 parts black masterbatch.

[0007] By adopting the above technical solutions, the low water absorption rate of polypropylene avoids the disadvantage of high water absorption rate of polyamide, and the high temperature resistance of polyamide compensates for the insufficient temperature resistance of polypropylene. Thus, the composite material can meet the temperature resistance requirements of long-term use at temperatures above 120℃ without deformation. The addition of high aspect ratio talc and chopped glass fiber enhances the structural stability of the material, reduces the warping deformation of the material, and requires almost no conditioning after injection molding, which improves production efficiency. It also makes the composite material have low mold shrinkage and linear thermal expansion coefficient, and can still maintain high dimensional stability after soaking in water for 168 hours.

[0008] Preferably, the polyamide comprises polyamide 6 with a viscosity of 2.0 in a mass ratio of (10-25):(25-31):(5-6), polyamide 6 with a viscosity of 2.4, and poly(m-phenylene adipamide).

[0009] By adopting the above technical solution, the weight-average molecular weight M of the polyamide 6 molecular chain with a viscosity of 2.0 is achieved. W The polyamide 6 molecular chain has a relatively low molecular weight and good fluidity, with a viscosity of 2.4 and a molecular weight average molecular weight M. W Relatively high viscosity, slightly poorer fluidity. Two polyamide 6 components of different viscosities are combined. The low-viscosity component provides excellent fluidity during processing, facilitating filler dispersion and injection molding; the high-viscosity component has higher molecular chain entanglement density and melt strength, which is beneficial for improving the heat distortion temperature and mechanical properties of the composite material. When the two are blended in an appropriate ratio, the heat resistance advantage of polyamide 6 can be maximized while ensuring processability, thus giving the composite material good temperature resistance.

[0010] Preferably, the high aspect ratio talc powder is surface modified with an aluminate coupling agent. The treatment step is to stir the high aspect ratio talc powder and the aluminate coupling agent in a high-speed mixer at 1500 r / min for 5 min.

[0011] By adopting the above technical solution, the dispersibility of the material is improved, allowing the high aspect ratio talc powder to be more evenly dispersed in the matrix, avoiding agglomeration. At the same time, the high aspect ratio characteristic can significantly reduce the shrinkage rate and deformation rate of the material, achieving low warpage deformation. After injection molding, almost no settling is required, improving production efficiency. On the other hand, the interfacial bonding of the material is enhanced, enabling the material to more effectively transfer stress when subjected to external forces or temperature changes, improving the material's temperature resistance and meeting the requirement of long-term use at temperatures above 120℃ without deformation.

[0012] Preferably, the PP / PA composite material further includes 2-6 parts of a nano-reinforcing agent, wherein the nano-reinforcing agent is a Janus-type amphiphilic hybrid nanoparticle with nano-silica as the core and polyamide 6 oligomer and maleic anhydride-grafted polypropylene grafted onto the surface, respectively.

[0013] Preferably, the particle size of the nano-silica is 20-50 nm, the number average molecular weight of the polyamide 6 oligomer is 1500-2500, and the grafting rate of the maleic anhydride-grafted polypropylene is 0.5%-1.2%.

[0014] By employing the above technical solution, the nano-reinforcing agent can simultaneously anchor to both the polypropylene and polyamide phases, significantly reducing the interfacial tension between the two phases, inhibiting phase separation, and improving interfacial bonding strength. Simultaneously, nano-silica acts as a heterogeneous nucleation agent, inducing the polyamide to form a fine and uniform crystalline structure, thereby increasing the heat distortion temperature. The nano-reinforcing agent, together with high aspect ratio talc and chopped glass fibers, forms a multi-scale reinforcing network, synergistically reducing the linear thermal expansion coefficient and shrinkage rate, significantly reducing warpage and meeting the requirement of long-term use without deformation above 120℃.

[0015] Preferably, the preparation method of the nano-reinforcing agent includes the following steps: Nano-silica was dried at 110℃ for 4 h, dispersed in anhydrous ethanol, and γ-glycidyl etheroxypropyltrimethoxysilane was added. The mixture was reacted at 60℃ for 6 h to obtain epoxy-modified nano-silica. Epoxy-modified nano-silica and amino-terminated polyamide 6 oligomers were added to xylene and reacted at 120℃ for 8 h to obtain PA6-g-SiO2. PA6-g-SiO2 and maleic anhydride-grafted polypropylene were reacted and blended in a twin-screw extruder at a mass ratio of 1:(1.8-2.2) at 190℃, and then extruded and granulated to obtain a nano-reinforcing agent.

[0016] By employing the above technical solution, γ-glycidyl etheroxypropyltrimethoxysilane is used to epoxy-modify nano-silica, providing reaction sites for subsequent grafting. Then, the epoxy-modified nano-silica is reacted with amino-terminated polyamide 6 oligomers to graft polyamide 6 segments onto the surface of the nanoparticles. Finally, it is reacted and blended with maleic anhydride-grafted polypropylene. The high shearing action of the twin-screw extruder achieves both chemical bonding and physical dispersion. The resulting nano-reinforcing agent has the characteristics of high grafting rate, good dispersibility, and strong compatibility with the matrix resin, thus possessing multiple functions such as interfacial compatibilization, heterogeneous nucleation, and size stability.

[0017] Secondly, this application provides a method for preparing PP / PA composite material for the middle frame of a commercial rice cooker, using the following technical solution: A method for preparing a PP / PA composite material for the inner frame of a commercial-grade rice cooker includes the following steps: a. Surface modification is performed by mixing high aspect ratio talc powder with aluminate coupling agent; b. Mix all components thoroughly according to the specified proportions; c. A twin-screw extruder is used for melt granulation, wherein chopped glass fibers are introduced through a side feeder. By employing the above technical solution, surface modification of high aspect ratio talc powder by mixing it with aluminate coupling agent alters the surface properties of the high aspect ratio talc powder, enhancing its compatibility and bonding with other components. This facilitates uniform dispersion during subsequent mixing and molding, thereby improving the overall performance of the composite material. Proportionally mixing each component ensures its full utilization, resulting in stable and expected composite material performance. Using a twin-screw extruder for melt granulation allows for better integration of components through the shearing and mixing action of the twin screws. The introduction of chopped glass fibers via a side-feed device prevents excessive breakage during initial mixing, maintaining a high aspect ratio and enhancing reinforcement. Composite materials prepared in this way exhibit high temperature resistance, meeting long-term use at temperatures above 120℃ without deformation; low warpage characteristics, requiring almost no post-injection molding, thus improving production efficiency; low die shrinkage and linear thermal expansion coefficient; and high dimensional stability after 168 hours of immersion in water.

[0018] Preferably, the extrusion temperature of the twin-screw extruder is set to 180℃, 240℃, 240℃, 240℃, 220℃, 220℃, 200℃, 200℃, 200℃, and 240℃ for the first to tenth stages, respectively.

[0019] By adopting the above technical solution, the relatively low temperature of 180℃ in the initial stage of extrusion allows the material to be initially softened by heat, avoiding premature decomposition or reaction of some components due to excessively high temperatures. The temperature is then gradually increased to 240℃, allowing the polypropylene, polyamide 6, and other polymer materials to fully melt and plasticize, ensuring uniform mixing of the chopped components and glass fibers. The subsequent gradual decrease in temperature, such as to 200℃, ensures full melting of the material and prevents degradation of the composite material caused by excessively high temperatures. This precise temperature setting ensures that the composite material is fully plasticized and uniformly mixed during extrusion, allowing the chopped glass fibers to be better dispersed in the matrix, enhancing the material's performance. The final composite material meets the requirement of long-term use at temperatures above 120℃ without deformation, and also possesses advantages such as low warpage, low die shrinkage, low linear thermal expansion coefficient, and high dimensional stability after immersion in water for 168 hours.

[0020] Preferably, the compatibilizer comprises a mixture of maleic anhydride-grafted polyolefin and maleic anhydride-grafted polypropylene in a mass ratio of 1:1, and the antioxidant system comprises antioxidant 1010, antioxidant 412S and antioxidant DSTP in a mass ratio of 1:1:2.

[0021] By adopting the above technical solution, the maleic anhydride groups in maleic anhydride-grafted polyolefin and maleic anhydride-grafted polypropylene molecules can react with polar groups such as amino groups in polyamide 6 molecules to form chemical bonds. At the same time, its polyolefin or polypropylene segments can be well compatible with polypropylene, thereby improving the comprehensive performance of the composite material. Antioxidant 412S is a thioester antioxidant that can decompose hydrogen peroxide and prevent it from further initiating free radical reactions. Antioxidant DSTP also has the function of decomposing hydrogen peroxide and has a synergistic effect with antioxidant 1010 and antioxidant 412S. It can inhibit the oxidation of composite materials during processing and use from different angles, effectively improve the antioxidant performance of composite materials, and thus enhance the stability and durability of composite materials in high temperature and high humidity environments, so that composite materials can meet the requirements for long-term use in environments above 120℃.

[0022] Preferably, the chopped glass fiber has a length of 3-5 mm and the surface of the chopped glass fiber is coated with a silane coupling agent treatment layer.

[0023] By adopting the above technical solution, and simultaneously coating the surface of the chopped glass fiber with a silane coupling agent treatment layer, the silane coupling agent can form chemical bonds between the glass fiber and the matrix resin, enhancing the interfacial bonding force between the two, enabling the glass fiber to more effectively transfer external forces to the matrix resin, further improving the strength and toughness of the composite material, helping the composite material meet the temperature resistance requirements of long-term use at temperatures above 120℃ without deformation, as well as reducing the warping deformation of the composite material and improving dimensional stability.

[0024] Preferably, the mixing process in step b includes a two-stage mixing process of first premixing polypropylene and polyamide, and then mixing them with other components in a secondary stage.

[0025] By adopting the above technical solution, the polypropylene and polyamide are first uniformly stacked in spatial position through premixing. After other components are added and mixed, a chemical reaction can be carried out more quickly at the interface between the two phases, which improves the dispersion effect and increases the reaction efficiency.

[0026] In summary, this application has the following beneficial effects: 1. Because the low water absorption of polypropylene in this application avoids the disadvantage of high water absorption of nylon 6, and the high temperature resistance of polyamide makes up for the insufficient temperature resistance of polypropylene, the composite material can meet the temperature resistance requirements of long-term use at temperatures above 120℃ without deformation. The addition of high aspect ratio talc and chopped glass fiber enhances the structural stability of the material, reduces the warping deformation of the material, and requires almost no conditioning after injection molding, which improves production efficiency. It also makes the composite material have low mold shrinkage and linear thermal expansion coefficient, and can still maintain high dimensional stability after soaking in water for 168 hours.

[0027] 2. In this application, the polyamide 6 with a viscosity of 2.0 has a relatively low molecular weight and good flowability, while the polyamide 6 with a viscosity of 2.4 has a relatively high molecular weight and slightly poor flowability. The two polyamide 6 components with different viscosities work together. The low-viscosity component provides excellent flowability during processing, facilitating filler dispersion and injection molding; the high-viscosity component has a higher molecular chain entanglement density and melt strength, which is beneficial for improving the heat distortion temperature and mechanical properties of the composite material. By blending the two in an appropriate ratio, the heat resistance advantage of polyamide 6 can be maximized while ensuring processability, thus giving the composite material good temperature resistance.

[0028] 3. In this application, high aspect ratio talc powder is mixed with aluminate coupling agent for surface modification. This alters the surface properties of the high aspect ratio talc powder, enhancing its compatibility and bonding with other components. This facilitates uniform dispersion during subsequent mixing and molding, thereby improving the overall performance of the composite material. Proportionally mixing each component ensures its full effectiveness, resulting in stable and expected composite material performance. A twin-screw extruder is used for melt granulation. The shearing and mixing action of the twin screws allows for better integration of the components. Short-cut glass fibers are introduced via a side-feeding device, preventing excessive breakage during initial mixing and maintaining their length and reinforcing effect. The resulting composite material exhibits high temperature resistance, meeting long-term use at temperatures above 120°C without deformation; low warpage characteristics, requiring almost no post-injection molding, thus improving production efficiency; low mold shrinkage and linear thermal expansion coefficient; and high dimensional stability after soaking in water for 168 hours. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the embodiments.

[0030] The raw materials used in this application are as follows: polypropylene was purchased from CNOOC Shell EP548R, high aspect ratio talc was purchased from Imerys+HAR large-layer talc, chopped glass fiber was purchased from Jushi Group 580, polyamide 6 was purchased from Zhejiang Hengyi Petrochemical HE2400A and HE2000A, poly(m-phenylene adipamide) was purchased from Shanghai Airegu MXD6, maleic anhydride-grafted polyolefin was purchased from DuPont FUSABOND N216, maleic anhydride-grafted polypropylene was purchased from Ningbo Nengzhiguang GPM200A, isophthalic dianhydride was purchased from Zhongyuan Chemical XDTA-K99, and antioxidants 1010 / 412S and DSTP were purchased from Beijing Jiyi General Purpose Model. Example

[0031] Example 1 A commercial-grade PP / PA composite material for the inner frame of a rice cooker comprises the following raw materials in parts by weight: 20 kg of polypropylene, 35 kg of polyamide, 10 kg of high aspect ratio talc, 7 kg of chopped glass fiber, 2.5 kg of compatibilizer, 0.3 kg of lubricant, 0.6 kg of antioxidant system, and 2 kg of black masterbatch. The polyamide comprises polyamide 6 with a viscosity of 2.0 and a viscosity of 2.4 in a mass ratio of 10:25:5, polyamide 6 with a viscosity of 2.4, and poly(m-phenylene adipamide). The compatibilizer comprises maleic anhydride-grafted polyolefin, maleic anhydride-grafted polypropylene, and m-phenylene dianhydride in a mass ratio of 1:1:0.5. The antioxidant system comprises antioxidant 1010, antioxidant 412S, and antioxidant DSTP in a mass ratio of 1:1:2. The chopped glass fiber has a length of 3 mm. The preparation method of the PP / PA composite material for the middle frame of the above-mentioned commercial-grade rice cooker includes the following steps: a. Surface modification was carried out by stirring high aspect ratio talc powder and aluminate coupling agent at 1500 r / min for 5 min. The mass ratio of high aspect ratio talc powder to aluminate coupling agent was 95:1. b. Mix all components thoroughly according to the specified proportions; c. A twin-screw extruder is used for melt granulation, wherein chopped glass fibers are introduced through a side feeder. The extrusion temperature of the twin-screw extruder is set to 180℃, 240℃, 240℃, 240℃, 220℃, 220℃, 200℃, 200℃, 200℃, and 240℃ for the first to tenth stages, respectively.

[0032] Example 2

[0033] A commercial-grade PP / PA composite material for the inner frame of a rice cooker comprises the following raw materials in parts by weight: 30 kg of polypropylene, 41 kg of polyamide, 6 kg of isophthalic dianhydride, 15 kg of high aspect ratio talc, 10 kg of chopped glass fiber, 5 kg of compatibilizer, 0.3 kg of lubricant, 0.6 kg of antioxidant system, and 2 kg of black masterbatch. The polyamide comprises polyamide 6 with a viscosity of 2.0 and polyamide 6 with a viscosity of 2.4 in a mass ratio of 25:31. The compatibilizer comprises a mixture of maleic anhydride-grafted polyolefin and maleic anhydride-grafted polypropylene in a mass ratio of 1:1. The antioxidant system comprises antioxidant 1010, antioxidant 412S and antioxidant DSTP in a mass ratio of 1:1:2. The chopped glass fiber has a length of 5 mm. The preparation method of the PP / PA composite material for the middle frame of the above-mentioned commercial-grade rice cooker includes the following steps: a. Surface modification was carried out by stirring high aspect ratio talc powder and aluminate coupling agent at 1500 r / min for 5 min. The mass ratio of high aspect ratio talc powder to aluminate coupling agent was 105:1. b. Mix all components thoroughly according to the specified proportions; c. A twin-screw extruder is used for melt granulation, wherein chopped glass fibers are introduced through a side feeder. The extrusion temperature of the twin-screw extruder is set to 180℃, 240℃, 240℃, 240℃, 220℃, 220℃, 200℃, 200℃, 200℃, and 240℃ for the first to tenth stages, respectively.

[0034] Example 3

[0035] The difference between Example 3 and Example 1 is that in Example 3, the polyamide contains polyamide 6 with a viscosity of 2.0 and polyamide 6 with a viscosity of 2.4 in a mass ratio of 10:15.

[0036] Example 4

[0037] The difference between Example 4 and Example 1 is that in Example 4, the polyamide contains polyamide 6 with a viscosity of 2.0 and polyamide 6 with a viscosity of 2.4 in a mass ratio of 10:40.

[0038] Example 5

[0039] The difference between Example 5 and Example 1 is that in Example 5, the mixing process in step b includes a two-stage mixing process of first premixing polypropylene and polyamide, and then mixing them with other components.

[0040] Example 6

[0041] The difference between Example 6 and Example 1 is that in Example 6, the mass ratio of high aspect ratio talc to aluminate coupling agent is 75:1.

[0042] Example 7

[0043] The difference between Example 7 and Example 1 is that in Example 7, the mass ratio of high aspect ratio talc to aluminate coupling agent is 120:1.

[0044] Example 8

[0045] The difference between Example 8 and Example 1 is that in Example 8, the PP / PA composite material also includes 3 kg of nano-reinforcing agent. The nano-reinforcing agent is Janus-type amphiphilic hybrid nanoparticles with nano-silica as the core and polyamide 6 oligomer and maleic anhydride-grafted polypropylene grafted on the surface, respectively. The nano-silica has a particle size of 30 nm and the polyamide 6 oligomer has a number average molecular weight of 2000. The preparation method of the nano-reinforcing agent includes the following steps: 100g of nano-silica was dried at 110℃ for 4h, dispersed in 500mL of anhydrous ethanol, and 5g of γ-glycidyl etheroxypropyltrimethoxysilane was added. The mixture was reacted at 50℃ for 4h, centrifuged, separated, washed with anhydrous ethanol, and vacuum dried to obtain epoxy-modified nano-silica. 50g of epoxy-modified nano-silica and 20g of amino-terminated polyamide 6 oligomer were added to 500mL of xylene and reacted at 100℃ for 6h. After centrifugation, separation, washing with anhydrous ethanol, and vacuum drying, PA6-g-SiO2 was obtained. PA6-g-SiO2 and maleic anhydride-grafted polypropylene were reacted and blended in a twin-screw extruder at a mass ratio of 1:1.8, and then extruded and granulated to obtain a nano-reinforcing agent.

[0046] Example 9

[0047] The difference between Example 9 and Example 1 is that in Example 9, the PP / PA composite material also includes 5 kg of nano-reinforcing agent. The nano-reinforcing agent is Janus-type amphiphilic hybrid nanoparticles with nano-silica as the core and polyamide 6 oligomer and maleic anhydride-grafted polypropylene grafted on the surface, respectively. The nano-silica has a particle size of 30 nm and the polyamide 6 oligomer has a number average molecular weight of 2000. The preparation method of the nano-reinforcing agent includes the following steps: 100g of nano-silica was dried at 110℃ for 4h, dispersed in 500mL of anhydrous ethanol, and 12g of γ-glycidyl etheroxypropyltrimethoxysilane was added. The mixture was reacted at 60℃ for 6h, centrifuged, separated, washed with anhydrous ethanol, and vacuum dried to obtain epoxy-modified nano-silica. 50g of epoxy-modified nano-silica and 40g of amino-terminated polyamide 6 oligomer were added to 500mL of xylene and reacted at 120℃ for 8h. After centrifugation, separation, washing with anhydrous ethanol, and vacuum drying, PA6-g-SiO2 was obtained. PA6-g-SiO2 and maleic anhydride-grafted polypropylene were reacted and blended in a twin-screw extruder at a mass ratio of 1:2.2, and then extruded and granulated to obtain a nano-reinforcing agent.

[0048] Example 10

[0049] The difference between Example 10 and Example 8 is that in Example 10, an equal amount of nano-silica is used instead of nano-reinforcing agent.

[0050] Example 11

[0051] The difference between Example 11 and Example 8 is that in Example 11, an equal amount of epoxy-modified nano-silica is used instead of the nano-reinforcing agent. Comparative Example

[0052] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no high aspect ratio talc was added in Comparative Example 1.

[0053] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that no chopped glass fibers were added in Comparative Example 2. Performance testing

[0054] PP / PA composite materials were prepared according to Examples 1-11 and Comparative Examples 1-2, and tested accordingly. Temperature resistance was tested at 120℃ for 168 hours according to GB / T7141-2008 "Test Method for Thermal Aging of Plastics". Warping deformation was tested according to GB / T 18029-2000 "Determination of Dimensional Changes in Plastic Products", and the deformation was recorded. Dimensional stability was tested after immersion in water for 168 hours according to GB / T 11547-2008 "Determination of Resistance to Liquid Chemical Reagents in Plastics", and the rate of change after immersion was recorded. The results are shown in Table 1.

[0055] Table 1 Performance test results of PP / PA composite materials Example 1 No deformation 0.05 0.02 Example 2 No deformation 0.06 0.03 Example 3 slight deformation 0.12 0.08 Example 4 Deformation 0.18 0.15 Example 5 No deformation 0.04 0.02 Example 6 No deformation 0.07 0.05 Example 7 No deformation 0.08 0.06 Example 8 No deformation 0.02 0.01 Example 9 No deformation 0.01 0.008 Example 10 slight deformation 0.09 0.05 Example 11 No deformation 0.05 0.03 Comparative Example 1 Severe deformation 0.35 0.25 Comparative Example 2 Deformation 0.22 0.18 As shown in Table 1, Examples 1-2, and Comparative Examples 1-2, the PP / PA composite materials prepared in Examples 1-2 exhibit excellent temperature resistance, extremely low warpage, and good dimensional stability after immersion in water. Table 1 data shows that Comparative Example 2, with only glass fiber added and no talc, had a warpage of 0.22 mm and a water-immersion change rate of 0.18%; Comparative Example 1, with only talc added and no glass fiber added, had a warpage of 0.35 mm and a water-immersion change rate of 0.25%; while Example 1, which combined glass fiber and talc, reduced its warpage to 0.05 mm and its water-immersion change rate to 0.02%. This indicates that glass fiber and high aspect ratio talc have a significant synergistic effect, and their combined use is superior to using either filler alone.

[0056] Examples 1-2 employ a specific ratio of polypropylene and polyamide system, combined with surface-modified high aspect ratio talc and silane-treated short-cut glass fibers, to form a synergistically reinforced network structure. This structure maintains shape stability even under long-term use at 120°C and exhibits minimal dimensional change after immersion in water, fully meeting the stringent operating conditions of commercial rice cooker frames.

[0057] Compared to Example 1, Examples 3-4 showed decreased temperature resistance, increased warpage, and increased dimensional change rate after immersion in water. Examples 3-4 altered the proportions of different viscosity components in the polyamide, demonstrating that a specific ratio of the two viscosities of polyamide 6 is crucial for forming a dense and uniform co-crystalline structure and achieving a balance between good processing flowability and final temperature resistance. Inappropriate proportions can lead to uneven phase morphology and decreased crystal integrity, thereby reducing the overall thermal and dimensional stability of the material.

[0058] Compared to Example 1, Example 5 showed a further reduction in warpage deformation, demonstrating the optimized effect of the premixing process. Example 5 employed a two-stage mixing process, first premixing polypropylene and polyamide, followed by a secondary mixing. This two-stage mixing promoted initial compatibility and molecular chain entanglement between the polypropylene and polyamide phases, providing a more stable matrix for the uniform dispersion of subsequent fillers and additives. Consequently, it further improved the interfacial bonding and overall uniformity of the composite material, reduced internal stress, and better controlled warpage deformation.

[0059] Compared to Example 1, Examples 6-7 show a slight increase in warpage deformation and dimensional change rate after immersion in water. Examples 6-7 adjusted the mass ratio of high aspect ratio talc to aluminate coupling agent. In Example 6, the coupling agent was relatively insufficient, which may have resulted in incomplete surface modification of the talc and slightly poor dispersibility in the matrix, affecting its reinforcing effect. In Example 7, the coupling agent was relatively excessive. Excessive coupling agent may remain in the system as a small molecule, slightly adversely affecting the material's thermal properties and dimensional stability.

[0060] Compared with Example 1, the addition of nano-reinforcing agents in Examples 8-9 further reduced warpage and water immersion expansion rates. This indicates that Janus-type nano-reinforcing agents can simultaneously anchor to the polypropylene and polyamide phases, reducing the interfacial tension between the two phases. The heterogeneous nucleation effect of nano-silica induces polyamide to form a fine and uniform crystalline structure, which forms a multi-scale reinforcing network with high aspect ratio talc and chopped glass fibers, thereby significantly reducing warpage and water immersion expansion rates.

[0061] Compared with Example 8, Examples 10-11 show that after replacing the nano-reinforcing agent with an equal amount of unmodified nano-silica in Example 10, the warpage deformation and water immersion change rate increased, and the temperature resistance decreased from no deformation to slight deformation. This indicates that unmodified nano-silica cannot form an effective anchor at the PP / PA two-phase interface, has poor dispersibility and is prone to agglomeration, and cannot exert the synergistic effect of interface compatibilization and nucleation modification. In Example 11, after replacing the nano-reinforcing agent with an equal amount of epoxy-modified nano-silica that has only been modified with silane, without grafting PA6 oligomer and PP-g-MAH, both the warpage deformation and water immersion change rate increased. Although silane modification improves the dispersibility of nanoparticles, the lack of PA6 and PP dual-grafted structure means that it cannot anchor the two phases at the same time, and the interface compatibilization effect is significantly reduced.

[0062] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A PP / PA composite material for the inner frame of a commercial-grade rice cooker, characterized in that: The raw materials include the following parts by weight: 20-30 parts polypropylene, 35-41 parts polyamide, 10-15 parts high aspect ratio talc, 5-10 parts chopped glass fiber, 2.5-5 parts compatibilizer, 0.3 parts lubricant, 0.6 parts antioxidant system, and 2 parts black masterbatch.

2. The PP / PA composite material for the middle frame of a commercial-grade rice cooker according to claim 1, characterized in that: The polyamide comprises polyamide 6 with a viscosity of 2.0 in a mass ratio of (10-25):(25-31):(5-6), polyamide 6 with a viscosity of 2.4, and poly(m-phenylene adipamide).

3. The PP / PA composite material for the middle frame of a commercial-grade rice cooker according to claim 1, characterized in that: The high aspect ratio talc powder is surface modified by an aluminate coupling agent. The treatment steps are as follows: the high aspect ratio talc powder and the aluminate coupling agent are stirred in a high-speed mixer at 1500 r / min for 5 min.

4. The PP / PA composite material for the middle frame of a commercial-grade rice cooker according to claim 1, characterized in that: The PP / PA composite material also includes 2-6 parts of nano-reinforcing agent, which is Janus-type amphiphilic hybrid nanoparticle with nano-silica as the core and polyamide 6 oligomer and maleic anhydride-grafted polypropylene grafted on the surface, respectively.

5. The PP / PA composite material for the middle frame of a commercial-grade rice cooker according to claim 4, characterized in that: The nano-silica has a particle size of 20-50 nm, the polyamide 6 oligomer has a number average molecular weight of 1500-2500, and the maleic anhydride-grafted polypropylene has a grafting rate of 0.5%-1.2%.

6. The PP / PA composite material for the middle frame of a commercial-grade rice cooker according to claim 4, characterized in that: The preparation method of the nano-reinforcing agent includes the following steps: Nano-silica was dried at 110℃ for 4 hours, dispersed in anhydrous ethanol, and γ-glycidoxypropyltrimethoxysilane was added. The mixture was reacted at 50-60℃ for 4-6 hours to obtain epoxy-modified nano-silica. Epoxy-modified nano-silica and amino-terminated polyamide 6 oligomers were added to xylene and reacted at 100-120℃ for 6-8 h to obtain PA6-g-SiO2. PA6-g-SiO2 and maleic anhydride-grafted polypropylene were reacted and blended in a twin-screw extruder at a mass ratio of 1:(1.8-2.2) at 190℃, and then extruded and granulated to obtain a nano-reinforcing agent.

7. A method for preparing a PP / PA composite material for the inner frame of a commercial-grade rice cooker according to any one of claims 1-6, characterized in that: Includes the following steps: a. Surface modification is performed by mixing high aspect ratio talc powder with aluminate coupling agent; b. Mix all components thoroughly according to the specified proportions; c. A twin-screw extruder is used for melt granulation, in which chopped glass fibers are introduced through a side feeder.

8. The method for preparing a PP / PA composite material for the inner frame of a commercial-grade rice cooker according to claim 7, characterized in that: The extrusion temperature of the twin-screw extruder is set to 180℃, 240℃, 240℃, 240℃, 220℃, 220℃, 200℃, 200℃, 200℃, and 240℃ for the first to tenth stages, respectively.

9. A method for preparing a PP / PA composite material for the inner frame of a commercial-grade rice cooker according to claim 7, characterized in that: The compatibilizer comprises a mixture of maleic anhydride-grafted polyolefin and maleic anhydride-grafted polypropylene in a mass ratio of 1:1, and the antioxidant system comprises antioxidant 1010, antioxidant 412S and antioxidant DSTP in a mass ratio of 1:1:

2.

10. A method for preparing a PP / PA composite material for the inner frame of a commercial-grade rice cooker according to claim 7, characterized in that, The mixing process in step b includes a two-stage mixing process: first, premixing polypropylene with polyamide 6, and then mixing it with other components in a secondary stage.