Polymer was used for the first time in 1835 by chemist Rnolt and the first commercial of application materials began with the discovery of rubber in 1834, however, the first synthetic plastic called cellulose nitrate discovered in 1862 and was entered the market in 1868, nylon in 1938, polyethylene in 1942, polypropylene in 1957, polybutylene in 1974 and polymer liquid crystals for the manufacture of electronic components were established in 1985. Polymers are divided to three types of natural polymers, modified natural and artificially. The first modern industrial plastics were introduced about 100 years ago but in recent decades occurred growth and variety in industry. So far, 60 very important polymer has established and the derivatives of that are more than 2000 and is still increasing.
Polyethylene or polyethene is one of the easiest and cheapest polymers. Polyethylene is solid, waxy and inactive. This material is obtained from the polymerization of ethylene (abbreviated PE).
Polyethylene pipes grades:
Classification of minimum required strength for bar
50 years strength
Over bar 6.3 and less than bar 7.99
Over bar 8 and less than bar 9.99
Over bar 10