PP sheet, also known as polypropylene (PP) sheet (pure PP sheet, modified PP sheet, reinforced PP sheet, PP welding rod), is a semi-crystalline material. It is harder and has a higher melting point than PE. Because homopolymer PP becomes very brittle above 0°C, many commercial PP materials are random copolymers with 1-4% ethylene or block copolymers with higher ethylene content. Product name: Copolymer PP materials have lower heat distortion temperature (100°C), lower transparency, lower gloss, and lower rigidity, but have higher impact strength.
The strength of polypropylene (PP) increases with increasing ethylene content. PP has a Vicat softening temperature of 150°C. Due to its high crystallinity, this material exhibits excellent surface stiffness and scratch resistance. PP does not suffer from environmental stress cracking. PP is typically modified by incorporating glass fibers, metal additives, or thermoplastic elastomers. The mean flow rate (MFR) of PP ranges from 1 to 40. PP materials with low MFR exhibit better impact resistance but lower tensile strength. For materials with the same MFR, copolymers have higher strength than homopolymers. Due to crystallization, PP has a relatively high shrinkage rate, typically ranging from 1.8% to 2.5%.
Furthermore, the uniformity of shrinkage is much better than that of materials like PE-HD. Adding 30% glass additive can reduce the shrinkage rate to 0.7%. Both homopolymer and copolymer PP materials have excellent resistance to moisture absorption, acid and alkali corrosion, and solvents. However, it is not resistant to aromatic hydrocarbon solvents (such as benzene) and chlorinated hydrocarbon solvents (carbon tetrachloride). PP also does not retain its oxidation resistance at high temperatures like PE.