PVC is a product based on two of the earth’s natural resources, salt and oil. Salt water electrolysis yields chlorine (in addition to caustic soda and hydrogen). Ethylene can be derived from naphtha when oil is refined. Chlorine and ethylene can be combined to form the monomer, vinyl chloride (VCM). PVC results from the polymerization of vinyl chloride.
PVC compounds are based on the combination of the polymer and additives. The compound is generated by intimately mixing together the ingredients, which is subsequently converted into the gelled article under the influence of heat (and shear). Depending on the type of PVC and additives, the compound prior to gelation can be a free-flowing powder (known as a dry blend) or a liquid in the form of a paste or solution.
PVC compounds can be formulated, using plasticizers, into flexible materials, usually called PVC-P. Compounds without plasticizer for rigid applications are designated PVC-U.
The compounding of PVC is the combination of appropriate additives with resin to regulate the behaviour of extrusion. It is one of the most important phases in PVC processing. PVC products are produced by mixing PVC powder with other additives aimed to improve and control the properties of the end-product. Low K-value-resins produce end products with poor physical properties. Suspension resins are generally less expensive and easier to process.