Methylene Chloride Migration in Polycarbonate Packages: Effect of Initial Concentration Profile

The migration of small molecules out of polymeric food packages into food can be predicted if the important thermodynamic and transport parameters are known. These parameters can be measured in convenient extraction experiments. The surface region of a sample used in extraction testing can be substantially depleted of migrant. When extraction data for a depleted sample are interpreted with respect to a mathematical model which assumes a flat initial migrant concentration profile, the thermodynamic and transport parameters are in error, resulting in an inaccurate prediction of long-time migration behavior. The results presented here demonstrate that even freshly manufactured polymer samples can be substantially surface depleted because migrant diffusion is very rapid at the high temperatures the polymer sees during manufacture.