What are the main types of polyethylene and their applications?

Polyethylene (PE) is the most widely produced plastic. Main types: LDPE (Low Density) - branched structure, flexible, used for films, bags, squeeze bottles, wire insulation. LLDPE (Linear Low Density) - linear with short branches, tougher than LDPE, used for stretch films, liners. HDPE (High Density) - linear structure, rigid, strong, used for bottles, pipes, containers, drums. UHMWPE (Ultra High Molecular Weight) - very high strength, wear resistant, used for bearings, medical implants. Production: LDPE by high-pressure free radical polymerization (1000-3000 bar), HDPE and LLDPE by catalytic polymerization (Ziegler-Natta or metallocene catalysts) at lower pressures. Properties depend on density, molecular weight, and branching.