Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications and produced via chain-growth polymerization from the monomer propylene. It belongs to the group of polyolefins and is the second-most widely produced commodity plastic after polyethylene.
Chemical and Physical Properties
PP is a semi-crystalline, non-polar polymer with the chemical formula (C₃H₆)ₙ. It is a white, mechanically rugged material characterized by low density—the lightest among all commercial plastics—which makes it ideal for weight-sensitive applications. Its properties are similar to polyethylene but it is slightly harder and exhibits superior heat resistance, with a high melting point around 320°F (160°C) that enables sterilization and high-temperature applications. The material demonstrates excellent chemical resistance to acids, bases, and solvents, high tensile strength (approximately 4800 psi), and exceptional fatigue resistance that allows it to withstand repeated flexing without cracking.
Key Characteristics
Polypropylene offers waterproof properties with extreme resistance to moisture absorption, and its semi-crystalline nature provides high flexural strength, making it resilient to general wear and tear. The material is non-toxic and FDA-approved for food contact, resistant to mildew, mold, rot and bacteria, and features excellent electrical insulation properties. It carries the SPI (Society of the Plastics Industry) recycling code number 5 and is recyclable, supporting sustainable manufacturing practices.
Major Applications
PP finds extensive use across multiple sectors including packaging and labeling, automotive components (bumpers, interior trim, instrument panels), textiles (ropes, thermal underwear, carpets), medical equipment (syringes, diagnostic devices, specimen bottles), consumer goods, reusable containers, laboratory equipment, and industrial applications such as chemical tanks, pipes, and films. Its combination of durability, chemical resistance, low cost, and versatility makes it suitable for both commodity and advanced functional applications including air and water filtration, battery separators, and protective clothing.
Kokel, Nicolas
