The excellent chemical resistance of polyvinyl chloride (P.V.C.) makes it particularly suitable for a wide range of applications in which this property is of primary importance.
Most of the data on the chemical resistance of P.V.C. has been obtained from short term immersion tests carried out in the laboratory. These tests involve qualitative assessment of the effect on a reagent of the surface of a specimen and it is difficult to use these results to predict the performance of fabricated forms in service. Attack of the surface of specimens in laboratory tests is recorded because it will probably be observed in practice, e.g. as a change of surface appearance, but it does not necessarily mean the P.V.C. is unsuitable for use in contact with the reagent. Even when chemicals actually dissolve or degrade the P.V.C., or cause marked swelling, other factors such as concentration of the reagent and the conditions of service have their effect. Only by trials on the fabricated article under actual or simulated service conditions can the suitability of P.V.C. in a specific application be ascertained.
Resistance of Plasticised P.V.C.
Plasticisers are incorporated in P.V.C. compounds so as to confer flexibility and softness. Plasticised compounds can cover a very wide range of flexibility and softness and will also differ in other respects e.g. tensile strength and resilience, according to the type and/or amount of plasticiser(s) used. For example, the type of plasticiser used will effect the chemical resistance, but in these notes it has been assumed that a commonly used, fairly resistant plasticiser dioctyl phthalate (DOP) would be present.
The amount of plasticiser incorporated will also effect the chemical resistance, an increase in plasticiser content leading to a deterioration in chemical resistance because the plasticiser is less resistant to attack than is the P.V.C.
Acid & Alkalis
Diluted acids and alkalis have little effect at room temperature, but at elevated temperatures some hydrolysis and extraction of plasticiser may occur. Concentrated acids and alkalis hydrolyse plasticiser slowly in the cold and more rapidly when heated.
The main effect of organic liquids on plasticised P.V.C. is to extract the plasticiser and this results in some hardening, particularly when the P.V.C. is removed from contact with the liquid. The compound may become rigid and less tough.
Most organic solvents will extract plasticiser and give rise to these effects, but with aromatic and chlorinated hydrocarbons, aliphatic and aromatic nitro compounds, ketones, aliphatic and cyclic ethers, this plasticiser extraction is accompanied by a softening of the P.V.C. and the overall effect is difficult to predict.
With certain solvents too, the plasticiser extracted is replaced by the solvents so that the compound remains flexible provided it remains in contact with the liquid. On allowing the solvent to evaporate the material will stiffen and will not soften on re-immersion.
Information in this publication and otherwise supplied to users is based on our general experience and is given in good faith, but because of the many particular factors which are outside our knowledge and control and affect the use of products, no warranty is given or is to be implied with respect to such information.
The relative resistances are listed in the following groups:
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