Using a simple diffusion model to predict residual monomer migration--considerations and limitations

A simple mathematical equation based on a diffusion model has been utilized recently to estimate migration of both acrylonitrile and styrene from polymers produced from these monomers which are used under a wide variety of food-contact applications. These calculated migration values have subsequently been used to estimate the US consumer's exposure to acrylonitrile and styrene from food stored in these materials. The basic assumptions integral to the model are discussed in relation to potential errors in migration estimates that could be experienced if the assumptions are not true. In addition to the discussion of the basic assumptions, factors affecting the migration predictions such as polymer 'ageing', temperature changes during the lifetime of the polymeric article, the effects of polymer-modifying materials (plasticizers, impact modifiers), and the physical form of the article or test sample are discussed.