Plasticised Polyvinyl Chloride (PVC)

Abstract

In this chapter, brief consideration will be given to a rubber-like product which is obtained by plasticising the rigid plastic known as polyvinyl chloride. The principal repeat unit present in polyvinyl chloride is shown at (LXXXIV). Polyvinyl chloride can be obtained in several forms, depending upon the method by which it is prepared. The common form is produced by Open image in new window the free-radical polymerisation of vinyl chloride, and in the unplasticised state has a glass-transition temperature in the region of 80–90°C. It is therefore apparent that, at normal temperatures, unplasticised polyvinyl chloride will behave as a rigid, glassy material. Unplasticised PVC is resistant to most acids and alkalis, although it is decomposed by sulphuric, nitric and chromic acids. It is soluble in a few organic solvents, such as tetrahydrofuran, and is swollen to varying extents by polar solvents such as ketones and esters, and by aromatic and chlorinated hydrocarbons. It is essentially unaffected by aliphatic hydrocarbons and oils. The solubility behaviour of polyvinyl chloride is determined primarily by the presence of the dipoles, associated with C—CI bonds, at regular intervals throughout the polymer sequence. In addition to its general chemical resistance, an important attribute of polyvinyl chloride is its low flammability. This also is a consequence of its high chlorine content.