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General process information
Like all plastic materials, PVC (Polyvinyl chloride) results from a series of processing steps that convert hydrocarbon-based raw materials (petroleum, natural gas or coal) into unique synthetic products called polymers. The vinyl polymer is unusual, however, because it is based only in part on hydrocarbon feedstocks: ethylene obtained by processing, or cracking, natural gas or petroleum. The other half of the vinyl polymer is based on the natural element chlorine.
Ethylene and chlorine are combined to form a liquid, ethylene dichloride (i) which is then heated to give a gas called vinyl chloride monomer (VCM).
A final step, called “polymerization,” converts the monomer into vinyl polymer. Pressure is applied to vinyl chloride (dispersed in water as a suspension or an emulsion) in high pressure chambers at temperatures of 50-70°C. The role of water is to remove and control the heat given off in the polymerization process.
PVC forms as tiny particles which grow and when they reach a desired size the reaction is stopped. The PVC is separated off and dried to form a white powder (PVC) or resin (S-PVC).
Vinyl resin, however, is still one step away from being a usable material: it must be combined with selected chemical additives and modifiers to achieve the various properties desired in vinyl end-products. Once these are added, the resulting material — vinyl compound — can be converted into an almost limitless range of applications.