Polypropylene Properties

The strength of PP increases as the ethylene content increases. The Vicat softening temperature of PP is 150 °C. Due to the high degree of crystallinity, this material has excellent surface stiffness and scratch resistance. There is no environmental stress cracking problem in PP. Typically, PP is modified by the addition of glass fibers, metal additives or thermoplastic rubber. The flow rate of PP has a MFR ranging from 1 to 40. Low MFR PP materials have better impact resistance but lower elongation. For materials of 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 to 2.5%. And the direction uniformity of shrinkage is much better than materials such as PE-HD. The addition of 30% glass additive can reduce the shrinkage to 0.7%. Both the homopolymer type and the copolymer type PP materials have excellent moisture absorption resistance, acid and alkali corrosion resistance, and solubility resistance. However, it is not resistant to aromatic hydrocarbons such as benzene solvents, chlorinated hydrocarbons (carbon tetrachloride) solvents, and the like. PP does not have oxidation resistance at high temperatures like PE.