PP is a semi-rigid, transparent, easily formed, economical polymer produced as a result of polymerization of propylene with the help of the ZIEGLER-NATTA Catalyst. Atactic, isotactic and syndiotactic PP of different properties can be prepared. The glassy transition temperature of isotactic PP is -10°C, and the melting temperature is about 160°C. PP has good chemical resistance, but it is affected by chlorine, nitric acid and other strong oxidizers. Although it is resistant to visible zone rays, UV-rays spoil the surfaces of materials made of PP. It can be burned, but it burns slowly. It is nontoxic.