Chemical stability of PP sheet
PP has excellent mechanical properties. Its yield strength, tensile strength, compressive strength, hardness, and elastic modulus are higher than HDPE. However, at room temperature and low temperature, due to its high molecular structure regularity, the impact strength is poor. PP has outstanding bending fatigue strength, good heat resistance, and good friction resistance, but it will be brittle at temperatures below 35 ° C, and its cold resistance is not as good as polyethylene; PP is very chemically stable Well, in addition to being attacked by concentrated sulfuric acid and concentrated nitric acid, it is relatively stable against various other chemical reagents, but low molecular weight aliphatic hydrocarbons, aromatic hydrocarbons, and atmospheric hydrocarbons can soften and swell polypropylene; high-frequency insulation of PP Excellent performance. Because it hardly absorbs water, the insulation performance is not affected by humidity. It has a high dielectric constant and can be used to make heated electrical insulation products. It has a high breakdown voltage and is suitable for electrical use. Accessories, etc.
PP has poor thermal stability and is very sensitive to light and heat. Adding a stabilization aid can improve its aging performance. PP products are sensitive to gaps, so care must be taken to avoid sharp corners when designing the mold, otherwise stress concentration will occur and the product's service life will be affected.
There are many molding methods for PP, such as injection molding, extrusion, blow molding, vacuum thermoforming, coating, rotary molding, welding, machining, electroplating and foaming, etc., and spraying on metal surfaces. That is to say, when it comes into contact with the metal wall for a long time, decomposition and carbonization will occur, so care must be taken during the processing to prevent the material from staying in the barrel for a long time. During injection molding, in order to facilitate plasticization, it is best to lengthen the diverter shuttle of the injection molding machine. If you want to shorten the injection cycle, you can also increase the injection temperature appropriately, but it is limited to not causing serious degradation. It is very important to choose an appropriate mold temperature during injection molding, because polypropylene molecules are prone to orientation, and after the molecular orientation, strain will occur and reduce the impact strength. Orientation phenomenon is most likely to occur during low temperature and high pressure injection, so the temperature cannot be too low (mold The best temperature is about 8OC, not lower than 50 ℃), otherwise the surface gloss of the molded product is poor, or defects such as welding marks are generated. Of course, the mold temperature should not be too high, too high mold temperature will cause the product to warp. PP has good secondary processing performance, and its printing performance is better than polyethylene. Products can be stamped, printed, glued, etc. Electroplating is used 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 processing technology, it can be divided into blown film, cast film, biaxially stretched film, etc .; injection molded products can be used in automobiles, electrical appliances, machinery, instruments, Radio, textile, national defense and other engineering accessories can also be used in daily necessities, turnover boxes, medical and health equipment, construction materials; extruded products, pipes, profiles, monofilaments, fishing ropes, packing straps, strapping ropes, woven bags, fibers , Composite coatings, sheets, plates, etc .; blow-molded hollow molded products, there are various small containers, etc .; rotary molding can make a variety of large-scale chemical storage tanks, containers, tanks, etc .; other products include calcium plastic plates, laminates, Synthetic paper, high foam structure foam, etc.