Unplasticised Polyvinyl Chloride (UPVC), also known as Rigid PVC, is a chemical compound of chlorine, carbon and hydrogen. ‘U’ stands for Unplasticised, , so that it is rigid for strong window frames.
It is a relatively simple plastic, consisting of 50% ordinary salt (sodium chloride, the source of the C in PVC). About 40% is ethylene, which is separated from fuel products during refining. Other additives include stabilizers and coloring. Ethylene is also found naturally in plants, leading to the prospect of totally renewable supply through bio-fuels.