Styrene migration from general-purpose and high-impact polystyrene into food-simulating solvents

General-purpose and high-impact polystyrenes (GPPS and HIPS, respectively) are used in many food-contact applications for the packaging of aqueous-based, fatty and dry foods. The correlation of residual styrene concentrations in polystyrene with styrene migration into food-stimulating solvents is of interest in order to predict the potential exposure of consumers to styrene from food-packaging applications. Studies of the migration of styrene into 8% ethanol and cooking oil from a GPPS and a HIPS polymer, each containing three different residual styrene levels, have been completed at temperatures ranging from 70 to 180 degrees F (21 to 82 degrees C). The results showed that the amount of styrene migrating from both polymers into cooking oil was proportional to the square root of the time of exposure, and the total amount of styrene migrating was proportional to the residual levels of styrene in the polymers. The calculated diffusion coefficients were found to be independent of the residual levels of styrene in a given polymer at a given temperature. While the partition equilibrium was not approached when the polymers were exposed to cooking oil, it was observed in the 8%-ethanol exposure studies. The calculated partition coefficients between the polymers and 8% ethanol appeared to be independent of the residual levels of styrene in the polymers at a given temperature. Linear relationships were observed between the logs of the diffusion and partition coefficients and the inverse of the absolute temperature of exposure.