Why Plasticisers Are Used

PVC is not the only polymer that can be plasticised, but less than 15% of all the plasticiser sold is used in any other type of resin. This is because a polymer can only be plasticised if it is (a) compatible with a softening agent and (b) slightly, but not very, crystalline in order to retain elastic recovery when mixed with a plasticiser. Not many polymers fulfil both these conditions. 

Other common polymers cannot absorb as much plasticiser as PVC can, without losing their mechanical properties and becoming putty-like, or imdergoing phase separation. Plasticised polystyrene does not have sufficiently good mechanical properties, and plasticisers do not mix well with polyolefins, polyamides or PET. This leaves only cellulose acetate, certain 

Special plasticisers have recently been proposed as a way of retaining polycarbonate s optical clarity, by inhibiting crystallisation. 

Plasticised or flexible PVC accoimts for about a third of all the PVC polymer sold. The proportion is decreasing in Einope, mostly because of competition from TPOs and TPEs and because of increasing use of rigid PVC in construction. 

Plasticisers must be price-competitive because, unlike many other additives, they often constitute a very large fraction of the product s weight. This explains the dominance of phthalates, which combine low cost with good technical qualities. 

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