White spirit solubility parameter

Of the instances of so-called solvent cracking of amorphous polymers known to the author, the liquid involved is not usually a true solvent of the polymer but instead has a solubility parameter on the borderline of the solubility range. Examples are polystyrene and white spirit, polycarbonate and methanol and ethyl acetate with polysulphone. The propensity to solvent stress cracking is however far from predictable and intending users of a polymer would have to check on this before use. 

While the Hildebrand solubility parameter is justified on theoretical concepts, the Kauri butanol test is an empirical method of testing based on the solubility of a natural gum in hydrocarbon solvents. It is a good guide to the solubility of resins in paraffinic, naphthenic and aromatic hydrocarbons and some chlorohydrocarbons. Many of the hydrocarbons used in industry are mixtures, such as special boiling point spirits and white spirit, and it is easier to measure their solvent performance rather than to try to calculate it (Table 13.5). 

Polymers of acrylonitrile are predicted to have good resistance to attack by aliphatic hydrocarbons (e.g. white spirit). These polymers will also be most soluble in solvents with higher solubility parameters (e.g. butyl glycol). 

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