Chemical stability of PP sheet
PP has excellent mechanical properties. Its yield strength, tensile strength, compression strength, hardness, elastic modulus, etc. are higher than HDPE, but at room temperature and low temperature, due to its high molecular structure regularity, the impact strength is poor ; PP has outstanding flexural fatigue strength, good heat resistance, and good friction resistance, but embrittlement will occur at a temperature lower than -35°C, and its cold resistance is not as good as polyethylene; PP has very good chemical stability Good, in addition to being corroded by concentrated sulfuric acid and concentrated nitric acid, it is relatively stable to various other chemical reagents, but low molecular weight aliphatic hydrocarbons, aromatic hydrocarbons and aromatic hydrocarbons can soften and swell polypropylene; PP high-frequency insulation Excellent performance. Because it hardly absorbs water, its insulation performance is not affected by humidity. It has a high dielectric coefficient and can be used to make heated electrical insulation products. Its breakdown voltage is also high, and it is suitable for electrical applications. Accessories etc.
PP has poor thermal stability and is very sensitive to light and heat. Adding stabilizing additives can improve its aging performance. PP products are sensitive to notches, so care must be taken to avoid sharp corners when designing the mold, otherwise stress concentration will occur, which will affect the life of the product.
There are many molding methods for PP, such as injection molding, extrusion, blow molding, vacuum thermoforming, coating, rotational molding, welding, machining, electroplating, foaming, etc., and spraying on metal surfaces. That is to say, decomposition and carbonization will occur when it is in contact with the metal wall for a long time, so be careful not to make the material stagnate in the barrel for a long time during the processing. During injection molding, in order to facilitate plasticization, it is best to lengthen the shunt shuttle of the injection molding machine. If you want to shorten the injection molding cycle, you can also increase the injection temperature appropriately, but it must not be severely degraded. It is very important to choose an appropriate mold temperature during injection molding, because polypropylene molecules are prone to orientation, which will cause strain and reduce impact strength after molecular orientation. Orientation is most likely to occur during low-temperature and high-pressure injection, so the temperature cannot be too low (mold The temperature is better to be around 8OC, not lower than 50℃), otherwise the surface gloss of the molded product will be poor, or defects such as weld marks will occur. Of course, the mold temperature should not be too high, too high mold temperature will cause the product to warp. The secondary processing performance of PP is very good, and its printing performance is better than that of polyethylene. The products can be bronzed, printed, bonded, etc., and electroplated for decorative parts such as instruments, meters, and electronics.
PP film is transparent and shiny, and has low permeability to water vapor and air. According to the processing technology, it can be divided into blown film, cast film, biaxially stretched film, etc.; injection molded products can be used for automobiles, electrical appliances, machinery, instruments, Engineering accessories such as radio, textile, national defense, etc., can also be used for daily necessities, turnover boxes, medical and health equipment, building materials; extruded products, including pipes, profiles, monofilaments, fishing ropes, straps, strapping ropes, woven bags, fibers , Composite coatings, sheets, plates, etc.; blow-molded hollow molded products, various small containers, etc.; rotational molding can manufacture various large chemical storage tanks, containers, tanks, etc.; other products include calcium plastic board, laminate, Synthetic paper, high foam structure foam, etc.
