pp material description
PP is a semi-crystalline material. It is harder than PE and has a higher melting point. Since homopolymer PP is very brittle when the temperature is higher than 0°C, many commercial PP materials are random copolymers with ethylene added or clamp copolymers with higher ethylene content. Copolymer PP material has lower thermal distortion temperature (100°C), low transparency, low gloss, low rigidity, but has stronger impact resistance. The strength of PP increases with the ethylene content. The Vicat softening temperature of PP is 150°C. Due to the high crystallinity, the surface stiffness and scratch resistance of this material are very good. PP does not have the problem of environmental stress cracking. Usually, the PP is modified by adding glass fiber, metal additives or thermoplastic rubber.
The flow rate MFR of PP ranges from 1 to 40. PP materials with low MFR have better impact resistance but lower elongation strength. For materials with the same MFR, the strength of the copolymer type is higher than that of the homopolymer type. Due to crystallization, the shrinkage rate of PP is quite high, generally 1.8~2.5. And the direction uniformity of shrinkage is much better than that of PE-HD and other materials. Adding 30% of glass additives can reduce the shrinkage to 0.7%. Both homopolymer and copolymer PP materials have excellent moisture resistance, acid and alkali corrosion resistance, and solubility resistance. However, it has no resistance to aromatic hydrocarbon (such as benzene) solvents, chlorinated hydrocarbon (carbon tetrachloride) solvents, etc. PP does not have oxidation resistance at high temperatures like PE.
