PVC: Production properties and uses PDF

In the plastics industry the terms PVC or pvc are used indiscriminately to describe a wide variety of different products characterised only by the fact that they are based on polymers of vinyl chloride, or copolymers of vinyl chloride with minor proportions of other monomeric compounds. The same terms are used to describe the polymers themselves, as well as compositions derived from these polymers by combination with other materials such as stabilisers, plasticisers, and fillers. In the extreme case of vinyl floor tiles the vinyl chloride content can be as low as 15 per cent, yet these products are frequently referred to as PVC. It would probably be unrealistic at this late stage of development to attempt to obtain widespread restriction of the application of the terms PVC and pvc to the material for whose chemical name they are abbreviations, namely polyvinyl chloride. Moreover, both forms of abbreviation are so convenient that it would also be both unrealistic to try to ban them altogether as well as embarrassingly restrictive to have to avoid using them, even in written form as in a Monograph such as this. Users of the terms should, however, ensure that the context is such that no ambiguity arises, and listeners and readers should exercise caution whenever the terms are used in circumstances which do not make their meaning clear. In this Monograph the abbreviations will be used for convenience wherever this is possible without loss of meaning. The author has found it convenient to use the capital form 'PVC' whenever reference is being made to a composition containing polymer and other ingredients' restricting the lower case 'pvc' to polymer without additives.

A second controversial issue arises when considering the full name for homopolymers of vinyl chloride. Over two decades ago it was proposed that where the name of a monomer comprises more than one word (e.g. vinyl chloride, methyl methacrylate) the name of its homopolymer should consist of the prefix 'poly' followed by the full name of the monomer enclosed in brackets. Thus for vinyl chloride the homopolymer should be called 'poly(vinyl chloride)' rather than 'polyvinyl chloride'. The advantages of using the former nomenclature seem to the present author too marginal to support the inconvenience of writing it. In any case, the form with brackets has gained little acceptance, and the older form without brackets will be used throughout this Monograph. Where copolymers are concerned there is perhaps a greater case for using the brackets, but this leads to rather clumsy names, and it is preferred here to avoid the prefix 'poly' altogether and to use an alternative such as 'vinyl chloride/vinyl acetate copolymer'.

There is also confusion about names for other materials referred to herein. Thus when polymers of ethylene were first introduced by I.C.I. in the 1930s they were dubbed 'polythene' and produced by LC.L under the trade-name' Alkathene'. Later other manufacturers regarded 'polythene' as a trade-name and preferred the term 'polyethylene'. Later still when I.U.P.A.C. agreed on a new nomenclature for olefines 'ethylene' became 'ethene', so that 'polyethene'became the logical term for the polymer. However, although this latter term is used in schools, it has not obtained acceptance in industry, and the latest I.U.P.A.C. recommendation has reverted to 'polyethylene', which is therefore used throughout this volume.

Another word applied to vinyl chloride polymers, which has a slight aura of ambiguity, is 'resin'. This word was originally applied to some synthetic polymers to indicate their resemblance to already known natural resins, and has since passed into more general usage to distinguish those polymers which are not rubber-like from those which are. In the particular context of PVC the word 'resin' is sometimes useful in distinguishing polymers as such from compositions containing them. Moreover, expressions such as 'vinyl resin' can be used where it is desired to embrace a whole variety of homopolymers and copolymers.

Edited by: George Matthews