What is polypropylene and what are its key properties?

Polypropylene (PP) is a thermoplastic polymer made from propylene monomer. Production: Ziegler-Natta or metallocene catalyst polymerization at 50-80C and 10-40 bar. Key properties: low density (0.90-0.91 g/cm3), high stiffness, good chemical resistance, excellent fatigue resistance (living hinge applications), higher melting point than PE (160-170C). Types: homopolymer (rigid), random copolymer (with ethylene, more flexible), and impact copolymer (contains rubber phase for toughness). Applications: automotive parts, packaging, textiles (fibers), furniture, medical devices, pipes. Second largest volume plastic after polyethylene. Global production exceeds 75 million tons/year.