Polypropylene is produced from liquid or gaseous propene, which is derived from gas oil, naphtha, ethane and propane. The process of creating polypropylene from propene is known as polymerization.
Polymerization uses Ziegler-Natta catalysts in order to create stable molecular chains. This is possible due to the asymmetrical nature of the propene molecule. After polymerization, the catalyst remains and must be removed before the polypropylene can be used. The final product has a range of positive attributes from recyclability to heat resistance. Therefore, polypropylene is a versatile polymer and is used in a range of products including clothing, carpeting, car bumpers and pipes. Over 52 million tons of polypropylene was manufactured worldwide in 2011.