PVC compounds also known as a dry blend are based on the combination of the PVC and additives that give the formulation necessary for the end-use application. The convention in recording the additive concentration is based on parts per hundred of the PVC resin (phr). 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/dry blend or a liquid in the form of a paste or solution. PVC compounds can be formulated for flexible materials using plasticisers, called PVC Plasicized Compounds and for rigid application without plasticizer called UPVC compound.
Rigid pipes are usually made of plain concrete, reinforced concrete, vitrified clay, cast iron and asbestos cement. Rigid pipes have sufficient strength to support loads even if no side support, such as backfill, is provided. However; this load carrying capacity can be significantly increased by providing proper bedding and backfill. Rigid pipes made of plain concrete are considered as failed if a crack or fracture is observed, however; for reinforced concrete pipes, cracks up to 0.01-inch are considered permissible.
The market is segmented based on the end-use applications and type of materials, diameter size of pipes, and regions with different criss-cross.