The characteristics of pp plastic include: good heat resistance, small density, good mechanical properties, good chemical properties, and most chemicals do not react, etc.; in addition, can be used in machinery and automotive manufacturing parts, electronic and electrical industrial devices, construction industry, etc., the following detailed description of the relevant content.
First, the characteristics of pp plastic
1, heat resistance is very good, pp products can be used for a long time in a high temperature environment below 100 degrees, and the temperature will not be significantly deformed to about 150 degrees.
2. The density is small, 0.81---0.91g/cm3, which is the smallest density among commonly used plastics.
3, pp material has good mechanical properties, with high heat resistance, good chemical properties, almost no water absorption, and the vast majority of chemicals do not react, pure texture, non-toxic, good electrical insulation.
4, if the storage is appropriate, it does not need to be dried.
5. The back pressure of the melt adhesive can be used for 5 bar, and the back pressure of the color powder can be appropriately adjusted.
6, the melting point is 160-175 °C, the decomposition temperature is 35O °C, but in the injection processing, the temperature setting can not exceed 275 °C, the mold temperature is 50-90 °C, for higher dimensional requirements with high mold temperature, the core temperature is more than 5 °C lower than the cavity temperature.
7. Injection pressure, using higher injection pressure and packing pressure, the packing pressure is about 80% of the injection pressure. At about 95% of the total stroke, the pressure is turned over, with a longer packing time.
8, injection speed, in order to reduce internal stress and deformation, high-speed injection should be selected, but if the surface of the engraved pattern appears by the gate diffusion of chiaroscuro stripes, then use low-speed injection and higher mold temperature.
9. Mold. The general runner passes through 4 to 7mm, the needle-shaped gate length is 1 to 1.5mm, and the diameter can be as small as 0.7mm. The shorter the length of the edge gate, the better, about 0.7mm, the depth is half of the wall thickness, the width is twice the wall thickness, and with the melt flow length in the mold cavity gradually increases, the mold must have good exhaust, the exhaust hole depth is 0.025mm - one by one 0.038mm, thick 1.5mm, to avoid shrinkage marks to use a large and round nozzle and circular runner, the thickness of the reinforcement should be small.
10. The viscosity of pp melt decreases significantly with the increase of shear speed, and is less affected by temperature.
Second, the industry application of PP plastics
1. Machinery and automobile manufacturing parts
Polypropylene has good mechanical properties, can be directly manufactured or modified to manufacture various mechanical equipment parts, such as the manufacture of industrial pipelines, agricultural water pipes, motor fans, infrastructure templates, etc. The modified polypropylene can be molded into bumpers, anti-scaffolds, car steering wheels, instrument panels and interior trim parts, which greatly reduces the weight of the body to achieve the purpose of saving energy.
2. Electronic and electrical industrial devices
Modified polypropylene can be used to make insulated shells for household appliances and washing machine liners, and is commonly used as insulation materials for wires and cables and other electrical appliances. Using 60 to 80 parts of homopolymer polypropylene by weight, 20 to 40 parts of ethylene-vinyl alcohol copolymer, 1 to 10 parts of compatile (reaction of polypropylene maleic anhydride graft and ethylene-vinyl alcohol copolymer), polypropylene composite materials mixed and refined at 170 °C ~ 190 °C have high toughness, their impact strength is as high as 210J/m, with high gas barrier performance, and the permeable vapor rate is close to 2000g·μm/(m2·24h). When preparing barrier films, the traditional film making process can be used for production, the process is relatively simple, and the production cost is lower.
3. Construction industry
Polypropylene fiber is the lightest of all chemical fibers, its density is (0.90 ~ 0.92) g / cm3, with high strength, good toughness, chemical resistance and microbial resistance and low price and other advantages, with glass fiber reinforced modified or modified with rubber, SBS modified polypropylene is used in a large number of construction project templates after foaming polypropylene can be used to make decorative materials. At the time of the earthquake, the destruction form of polypropylene fiber ceramic concrete was plastic destruction, with no fragment peeling. The use of polypropylene fiber ceramic concrete is safer than plain ceramic concrete.
4. Agriculture, fishery and food industry
Polypropylene can be used to make greenhouse gas, mulch film, culture bottles, agricultural tools, fishing nets, etc., and to make food turnover boxes, food bags, beverage packaging bottles, etc. Reactive blending with waste PET (polyethylene terephthalate) is made of multifunctional waste PET, and in situ fiber forming composite materials are made by composite multifunctional waste PET with polypropylene in situ fibrosis. The composite material has the structural characteristics of waste PET formation of special-shaped microfibers, waste PET microfibers and PP matrix resins form a moderate flexible and strong combination of interface, waste PET and PP composite prepared in situ fiber-forming composites the toughness rigidity is significantly improved than PP, the reproducibility of mechanical properties is quite good. The recycling of waste, that is, waste PET, which is generated in Large Quantities every year in China, has significant economic and social benefits.
5. Textile and printing industry
Polypropylene is the raw material of synthetic fiber, polypropylene fiber is widely used to make lightweight and beautiful durable textile supplies, the application of polypropylene material printing out of the picture is particularly bright, bright and beautiful. [6]
6. Other industries
In the chemical industry, polypropylene can be used in the preparation of a variety of corrosion-resistant conveying pipelines, storage tanks, valves, packing towers in the lining of special-shaped fillers, filter cloths, corrosion-resistant pumps and corrosion-resistant containers; in medicine, it can be used to make medical appliances; polypropylene can also be developed and applied in the energy field through grafting, compounding and blending processes.