Plasticisers may sometimes bleed or evaporate from the surface of the PVC product after years of use.
Plasticisers may also migrate to other materials which come in contact with PVC products. Such cases can be seen when plasticisers of low-molecular weight or low compatibility (low miscibility) are used, or when large amounts of plasticisers are used. This can be a disadvantage of flexible PVC products but may be alleviated by using plasticisers having higher molecular weight.
The graph shows the result of accelerated tests on the evaporation of plasticisers. Test sheets using plasticisers are heated in an oven. Heat loss (weight loss) due to evaporation of plasticisers is shown.