Application of modified PP (polypropylene) in household appliances

The modification of polypropylene materials is generally through several ways such as mineral strengthening and toughening, weathering modification, glass fiber reinforcement and flame retardant modification. Each modified product has a large number of applications in the field of household appliances.

Mineral strengthening and toughening is one of the most common modification pathways. The mineral added to the polypropylene raw material is usually calcium carbonate, talc, wollastonite, glass microbeads, mica powder or the like. These minerals not only improve the mechanical properties and impact toughness of polypropylene materials to a certain extent, reduce the molding shrinkage of polypropylene materials to enhance their dimensional stability, and because of the huge cost difference between minerals and polypropylene matrix, The cost of the polypropylene material can be greatly reduced. At present, the inner cylinder of the pulsator washing machine and the drum washing machine generally use mineral reinforced and toughened polypropylene material to replace the early stainless steel inner cylinder. After the mineral material is strengthened and toughened by the mineral material, the original strength, the gloss is not good, and the shrinkage is too large. In addition to the inner cylinder of the washing machine, the modified polypropylene is also used to make components such as pulsators and clothes outlets. Only Haier Group uses about 1700 tons per year (the weight of each washing machine cylinder is about 2kg). In addition, many parts of the microwave oven are also made of mineral-reinforced and toughened polypropylene material. Due to the addition of minerals, the heat-resistant temperature of the polypropylene material can be further improved on the basis of the higher heat-resistant temperature of the polypropylene material to meet the high temperature requirements of the microwave oven. For example, the modified sealing material of the microwave door body, the microwave speaker flare, the horn bracket, and the like are all made of the modified polypropylene material. In addition, the shelves on the refrigerator are now basically made of mineral-reinforced and toughened polypropylene. Due to the integral injection molding with the glass panel, the problem of panel drowning of the original ABS material is well solved.

The weather-resistant modified polypropylene material is a problem that the polypropylene contains an unstable tertiary carbon group, which is susceptible to aging degradation after light, heat and oxygen, resulting in discoloration and strength drop, thereby limiting its appearance on outdoor products. application. Therefore, by weathering the polypropylene, the service life of the polypropylene material in outdoor harsh weather conditions can be greatly improved. The modified material is mainly used for manufacturing household appliances exposed to the open air all the year round, especially for manufacturing the outdoor main casing of the air conditioner, instead of the traditional metal sprayed plastic outer casing, thereby overcoming the production of the original metal sprayed plastic outer casing. The complex process, high cost, heavy weight, easy to rust (can affect the performance and service life of the whole machine) and other shortcomings, ultimately reduce the labor intensity of workers, reduce energy consumption, and extend the service life. This technology was first developed and put into use by the Japanese Sumitomo and Mitsubishi Chemical Co., Ltd. in the early 1990s.

The glass fiber reinforced polypropylene material is the mechanical property of the polypropylene material itself. The requirements of the engineering structural parts are very different. Generally, the tensile strength is between 20 and 30 MPa, the bending strength is between 25 and 50 MPa, and the flexural modulus is between 800 and MPa. Between 1500MPa. If you want to use it on engineering structural parts, you must use glass fiber for reinforcement. In general, the mechanical properties of glass-reinforced polypropylene products can be multiplied or even multiplied. Specifically, the tensile strength is 65 to 85 MPa, the bending strength is 70 to 95 MPa, and the flexural modulus is 3,000 to 4,500 MPa. This mechanical strength is comparable to ABS and reinforced ABS products, and is more resistant to heat. Generally, the heat resistant temperature of ABS and reinforced ABS is between 80 ° C and 98 ° C, and the heat resistance temperature of the glass fiber reinforced polypropylene material can reach 135 ° C to 145 ° C. It can be used to make axial fans and cross-flow fans in refrigeration machines such as refrigerators, air conditioners, etc., at a much lower cost than ABS enhanced products or AS enhanced products. In addition, it can also be used to manufacture the inner cylinder of a high-speed washing machine to meet its high mechanical performance requirements.

Flame-retardant modified polypropylene materials are used to avoid fires. Many countries now require that the materials used in electronic and electrical components in household appliances must be flame-retardant. Generally, the flame retardant grade V0 of UL94 is required. Since polypropylene is a flammable material, it is generally used in the flame retardant modification of Br/Sb composite flame retardant. Through flame retardant modification, polypropylene products can be extinguished in case of fire, and can withstand 6500C or even 7500C glow wire without burning. Such flame retardant modified polypropylene materials are generally used to make components such as washing machine control trays, wire controller housings, refrigerator evaporating dishes, air ducts, and the like that are potentially hazardous to combustion.