Diffusion Coefficients of Organic Compounds in Molten High‐Impact Polystyrene

ABSTRACT Polystyrene (PS) is a widely used packaging material, but its recycling for food‐contact applications is still limited, partly due to a lack of quantitative data on the migration behavior of potential contaminants. This study investigates the diffusion behavior of organic compounds in high‐impact polystyrene (HIPS) under vacuum and controlled thermal conditions. Virgin HIPS was intentionally spiked with five organic compounds covering a broad range of molecular weights and polarities. The contaminated material was pressed to plates with various thicknesses which were then exposed to defined combinations of temperature and residence time in a vacuum oven. Initial and residual concentrations were quantified using gas chromatography, and the data were used to calibrate a one‐dimensional diffusion model based on Fick's second law including Arrhenius‐type temperature dependency. The results confirm that the model adequately describes the experimental data and allows reliable estimation of diffusion coefficients. Clear correlations were observed between the diffusion coefficients and the molecular weight, polarity, and volatility (boiling point) of the surrogates. These findings provide fundamental parameters for predicting diffusion‐driven mass transfer in HIPS processing and establish a scientific basis for future risk assessments of recycled PS in applications requiring particularly high purity standards, such as food‐contact materials.