Polypropylene (PP) is a thermoplastic from the polyolefin group. It is a semi-rigid, translucent polymer with good toughness and weather resistance properties, low water absorption and is easily moulded to desired shapes. PP is a largely non-polar, partially crystalline thermoplastic with a crystallinity of 60 to 70% and a density of 0.90 to 3 0.91 g/cm which is amongst the lowest for all plastics. It is generally available in three advanced forms:
PP-Homopolymer (PP-H): Produced by a continuous chain of polypropylene units which results in a high stiffness material. Advanced homopolymer types like beta nucleated PP, are used to make piping systems and sheets.
PP-Copolymer (PP-C): Produced by adding 4-15% ethylene to the polypropylene gives much improved impact strength and considerably lowers the brittle point to below normal service temperatures i.e. -15°C to -20°C.
PP Random Copolymer (PP-R): Random copolymer polypropylene is a clear, semi-crystalline polymer which exhibits high stiffness, better impact strength and good electrical insulation properties.
Other options in PP include fire retardant and electro-conductive grades. PP can also be UV stabilized.