Polyvinyl chloride (PVC) occurs as white, amorphous, odourless powder. It is soluble in nitrobenzene, cyclohexanone, and tetrahydrofuran but insoluble in vinyl chloride. It is resistant to dilute alkalis and acids but is attacked by concentrated nitric and chromic acids.
Two types of PVC homopolymer are produced: rigid resins which are inflexible and hard; and flexible resins which contain a large proportion of plasticiser to make them soft and can be stretched. Products made from rigid PVC include pipe and conduit and roofing tiles.
Flexible PVC finds outlets in wire and cable coating, flooring, coated fabrics and shower curtains. Other outlets for flexible PVC are film and sheet and flooring.
Polymerisation is normally performed at 40-70oC with the vinyl chloride monomer (VCM) in a liquid state under pressure in a batch reactor. Suspension polymerisation is the most common PVC process because the resins produced are the most versatile and suitable for a wide range of applications.
The resin produced from the polymerisation process is hard and brittle and requires conversion into a compound by the incorporation of additives such as plasticisers, modifiers, stabilisers and processing aids before conversion into finished products.