PP is a semi-crystalline material, harder and with a higher melting point than PE. Due to the brittleness of homopolymer PP above 0°C, many commercial PP materials are produced by adding 1-4% random copolymers or block copolymers with higher ethylene content. Copolymer PP materials have lower heat distortion temperatures (100°C), lower transparency, lower luster, and lower rigidity, but offer greater impact strength. The strength of PP increases with the addition of ethylene content. The Vicat softening temperature of PP is 150°C. Due to its high crystallinity, this material exhibits good surface rigidity and scratch resistance.

PP does not have the issue of environmental stress cracking. Typically, modifications to PP are achieved by adding glass fiber, metal additives, or thermoplastic rubber. The melt flow rate (MFR) of PP ranges from 1 to 40. PP materials with lower MFR have better impact resistance but lower elongation strength. For materials with the same MFR, the copolymer type has higher strength than the homopolymer type. Due to crystallization, PP has a relatively high shrinkage rate, generally 1.8% to 2.5%. Moreover, its shrinkage rate uniformity is much better than that of PE-HD and other materials. Adding 30% glass additives can reduce the shrinkage rate to 0.7%. Both homopolymer and copolymer PP materials have excellent moisture resistance, resistance to acid and alkali corrosion, and resistance to solubility. However, it is not resistant to aromatic solvents (such as benzene) and chlorinated hydrocarbons (e.g., carbon tetrachloride) solvents.