Minimising Plasticiser Loss

Loss of plasticiser over time leads to embrittlement and component failure, adversely affecting adjacent plastic components, notably those made of polystyrene, ABS or polycarbonate. 

Several other approaches to reducing plasticiser loss, besides using DINP and similar products, have been considered. Alloys of PVC with polymers like thermoplastic polyurethanes, EVA and nitrile rubber can give fairly flexible materials without using plasticisers at all. Appropriate blends can offer flexibility and low temperature toughness. 

Teknor Apex has alloyed PVC with metallocene polyolefin elastomers to make a range of new materials called FreeFlex. They resemble flexible PVC, but are about 50% more expensive they are intended for flexible hose and tubing and flexible sheeting. The combination of PVC with polyolefins had been unsatisfactory until comparatively recently, when more effective compatibilisers became available. 

Alternatively PVC can be crosslinked with dithiocarbamates to reduce plasticiser migration, and a copolymer of PVC can also be crosslinked when modified with acrylic groups. Applying acrylic topcoats such as Rohm s Degalan also helps to minimise loss through the smface. 

Researchers in Germany claim that a titanimn-based surface coating can cut plasticiser migration from flexible PVC products. The University of Erlangen has co-operated with GfE Medizintechnik to develop an inert, biocompatible 30 nm titanium based system called MigraStop to prevent phthalate migration in medical equipment. 

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The excellent properties of EVOH resins in terms of high gas, hydrocarbon and aroma barrier and transparency have allowed them to become widely implemented in many commercial applications where high barrier properties are needed to minimise product losses due to deterioration. Despite the excellent performance of these materials in high barrier food packaging applications, the materials are easily plasticised by moisture and, consequently, in most packaging applications are commonly encapsulated in multi-layer structures between hydrophobic polymers such as PP or PE. 

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