Current situation and Prospect of modified PP plas

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Current situation and Prospect of modified PP plastic materials for household appliances

hips and ABS are the first plastic materials used in household appliances. Due to the high price of hips and ABS resins, foreign countries have gradually developed PP (polypropylene) modified materials suitable for household appliance parts, and partially replaced hips and ABS resins in household appliance products with their advantages of low cost, light weight and good performance

As one of the four general plastic materials, PP has excellent comprehensive properties, good chemical stability, good molding performance and relatively low price; However, it also has some disadvantages, such as low strength, modulus, hardness, poor low-temperature impact strength, large molding shrinkage, easy aging and so on. Therefore, it must be modified to meet the needs of products. The modification of PP materials is generally through the addition of minerals to strengthen and toughen, weather resistance modification, glass fiber reinforcement, flame retardant modification and super tough modification. Each modified PP has a large number of applications in the field of household appliances. This paper will describe the application status and development trend of modified PP in household appliances

mineral filling modification PP

mineral filling modification is the most widely used modification method. Add calcium carbonate, talc powder, wollastonite, glass beads, mica powder and other minerals to PP raw materials. These minerals can not only improve the mechanical properties and impact toughness of PP material to a certain extent, reduce the molding shrinkage of PP material to strengthen its dimensional stability, but also greatly reduce the cost of PP material due to the huge cost difference between minerals and PP matrix

at present, the application parts of mineral filled modified PP in household appliances mainly include: inner barrel, impeller and clothes taking port of wave wheel washing machine and drum washing machine; Sealing strip of microwave oven, loudspeaker bell mouth and loudspeaker support; Shelf of refrigerator; Shell and base of rice cooker, etc

the inner barrel of washing machine was originally made of stainless steel. In the 1990s, American Basel company and Korean SamSung company began to study "using modified PP to replace stainless steel to make the inner barrel of drum washing machine", and realized commercialization. Since then, washing machine enterprises began to use this modified material in large quantities. The mineral content of this material is as high as 40%, its tensile strength is 33mpa, the elongation at break is more than 90%, and the notch impact strength is about 10kj/m2. At present, this modified PP is not only used to make the inner barrel of washing machines, but also used to make parts such as wave wheels and clothes taking openings. The annual consumption of Haier group alone is about 1700 tons (each inner barrel of washing machines weighs about 2 kg)

many parts of microwave ovens are also made of mineral reinforced and toughened PP materials. For example, the sealing strip of the microwave oven door and the loudspeaker of the microwave oven have innovated the coating technology, such as the horn mouth and horn support. Due to the addition of minerals, the heat-resistant temperature of PP material can be further improved on the basis of its high heat-resistant temperature, so as to meet the requirements of microwave ovens for high temperature

in recent years, the price of raw materials has soared significantly. Under the pressure of cost, many injection molding manufacturers are considering replacing ABS with polystyrene or replacing polystyrene products with modified PP products to reduce costs, so there are a large number of examples of PP materials successfully replacing polystyrene. For example, after choosing mineral reinforced and toughened PP material to replace the original polystyrene material for injection molding refrigerator drawers, the cost per ton of raw materials can be saved by 1500~2000 yuan. Due to the large consumption, Haier group alone consumes about 1000 tons of this PP modified material a year. In addition, many refrigerator enterprises also use mineral reinforced and toughened PP materials for the refrigerator panel, such as Kelon Electric Appliance, Meiling electric appliance and other companies. Although the mechanical properties of PP modified material are slightly worse than that of polystyrene, and there are problems such as distortion, shrinkage marks and poor rigidity. Taking advantage of the good toughness and high MFR of PP material, the product is redesigned, and solid stiffeners are added at the junction of the side and top of the product. Such a design basically solves the problem of poor rigidity of the product, which can save a lot of material costs

PP modified materials used for plastic parts on rice cookers are mainly divided into high gloss and heat-resistant. The shell of rice cookers requires high gloss, while the base requires high heat-resistant materials

the shell of rice cookers used to be mainly made of ABS. Due to cost pressure, now modified PP is mainly used to replace ABS. The shell material of rice cooker requires high gloss and low shrinkage, and the shrinkage can be improved by mineral filling. However, in the selection of minerals, glass beads, barium sulfate, calcium carbonate, etc. that have little impact on the surface gloss should be selected. If necessary, the surface gloss can also be improved by nucleating agents, lubricants, fluorescent agents, etc

weather resistant modified PP

because PP contains unstable tertiary carbon groups, it is prone to aging and degradation after the action of light, heat and oxygen, resulting in discoloration, strength reduction and other problems, which limits its application in outdoor products. Therefore, the weatherability modification of PP can greatly improve the service life of PP materials under outdoor adverse weather conditions. The modified material is mainly used to manufacture household appliances that have been exposed for many years and focus on graphene industrialization and subsequent utilization research, especially for the manufacture of outdoor host shell of air conditioner to replace the traditional metal spray shell

the outdoor unit shell of the air conditioner should withstand the test of different climatic conditions such as sunshine, rain and severe cold, and should meet the requirements of long-term use. The technology of using plastic instead of metal spray was first developed and put into use by Sumitomo and Mitsubishi Chemical Co., Ltd. in the early 1990s. This technology overcomes the shortcomings of the original metal spray shell, such as complex manufacturing process, high cost, large weight, easy to rust (which can affect the performance and service life of the whole machine), and finally reduces the labor intensity of workers, reduces energy consumption Extended service life. In addition to the shell of the outdoor unit of the air conditioner, weatherproof PP is also used for the axial fan blades of the outdoor unit of the air conditioner and the air outlet of the heater. In recent years, with the increase of the output of air conditioners, the application of modified weather resistant PP in the product market is also gradually increasing

flame retardant modified PP

in order to avoid fire, many countries now require that the materials used in electronic and electrical components of household appliances must be flame retardant. Among flame retardant PP, 63% are required to reach UL94V-0 level, 23% are required to reach UL94V-2 level, 12% are din4102b1 level, and 1% are other flame retardant levels. The high crystallization and flammability of PP make it difficult to reach the high flame retardant level required by electrical and other industries, and the cost increases a lot. However, with the improvement of social requirements for flame retardancy of plastic products, the proportion of flame retardant PP will increase. At present, the annual growth rate of flame retardant PP is 8%

because PP is a flammable material, br/sb composite flame retardant is generally used in the market to modify its flame retardancy. Through flame retardant modification, PP products can reach UL94V-0 level, and can withstand 650 ℃ or even 750 ℃ hot wire without ignition. This flame-retardant modified PP material is generally used to make components with potential Combustion Hazards, such as TV shell, washing machine control panel base, wire controller shell, refrigerator evaporating dish, ventilation duct and so on

glass fiber reinforced modified PP

generally, the tensile strength of PP material is between 20m~30mpa, the bending strength is between 25m~50mpa, and the bending modulus is between 800m~1500mpa. If you want to use PP in engineering structural parts, you must use glass fiber for reinforcement

generally speaking, the mechanical properties of PP products reinforced by glass fiber can be doubled or even several times improved. Specifically, the tensile strength reaches 65mpa~90mpa, the bending strength reaches 70mpa~120mpa, and the bending modulus reaches 3000mpa~4500mpa. Such mechanical strength is completely comparable to ABS and reinforced ABS products, and it is more heat-resistant. Generally, the heat-resistant temperature of ABS and reinforced ABS is between 80 ℃ ~98 ℃, while the heat-resistant temperature of glass fiber reinforced PP material can reach 135 ℃ ~145 ℃. It can be used to make axial flow fans and cross flow fans in refrigerators, air conditioners and other refrigeration machines, and its cost is much lower than that of ABS enhanced products. In addition, it can also be used to manufacture the inner barrel, wave wheel and belt pulley of high-speed washing machine to meet its high requirements for mechanical performance. It can also be used in places where the strength of materials with high requirements for temperature resistance is higher, such as rice cooker base and handle, electronic microwave oven and so on

development trend and Prospect of modified PP

modified PP has a very good application prospect in the household appliance industry. On the one hand, China has become the production center of household appliances in the world, and has a number of influential production enterprises, which can actively choose materials; On the other hand, industry competition also urges enterprises to apply materials with more reasonable cost performance. From the perspective of the development of home appliance technology in the future, the humanization of home appliances will be more prominent. According to the influence of the size of different parts of the structure on the deflection of the beam and the characteristics of structural stress distribution, the product variety will be more complete, and the traditional home appliances will develop in the direction of miniaturization and large-scale. The continuous emergence of new products also puts forward higher requirements for PP modification. Modified PP will have four main development trends:

1 High rigidity, high gloss PP. This product may replace PS and ABS in some household appliances, especially small household appliances

2. Halogen free flame retardant PP. With the implementation of the European Union RoHS decree and the attention paid by all countries to environmental protection, the research and development of halogen-free flame retardant PP is urgent, and the market prospect is broad

3. Long glass fiber reinforced PP. Ordinary short glass fiber reinforced PP, because the glass fiber contained is short, easy to warp, low impact strength, easy to deform when heated, long glass fiber can overcome the above defects of short glass fiber, and the products have better surface, higher service temperature, higher impact strength, and can be used in refrigerators and kitchen appliances with high heat resistance

4. Antibacterial PP. This kind of plastic is a new functional polymer material with bactericidal and antibacterial properties. It can be used in washing machine liners and plastic parts in refrigerators, and has a broad prospect. (end)

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