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Styrene migration from general-purpose and high-impact polystyrene into food-simulating solvents
P G Murphy1, D A MacDonald, T D Lickly
1Analytical Chemistry Laboratory, Dow Chemical Company, Midland, MI 48674.
Summary
Styrene migration from general-purpose and high-impact polystyrene packaging into food simulants was studied. Migration into cooking oil increased with residual styrene and exposure time, while migration into ethanol reached equilibrium.
Area of Science:
- Polymer Science
- Food Packaging Safety
- Analytical Chemistry
Background:
- General-purpose and high-impact polystyrenes (GPPS and HIPS) are widely used in food packaging.
- Understanding styrene migration is crucial for assessing consumer exposure from food-contact materials.
Purpose of the Study:
- To correlate residual styrene levels in polystyrene with migration into food simulants.
- To predict potential consumer exposure to styrene from packaging applications.
Main Methods:
- Studied styrene migration from GPPS and HIPS into 8% ethanol and cooking oil.
- Tested polymers with varying residual styrene levels at temperatures from 70 to 180°F (21 to 82°C).
- Analyzed migration kinetics, diffusion coefficients, and partition coefficients.
Main Results:
- Styrene migration into cooking oil was proportional to the square root of time and residual styrene levels.
- Diffusion coefficients were independent of residual styrene levels at a given temperature.
- Partition equilibrium was reached with 8% ethanol but not with cooking oil.
- Partition coefficients in 8% ethanol were independent of residual styrene levels.
Conclusions:
- Styrene migration behavior differs significantly between fatty (cooking oil) and aqueous (8% ethanol) simulants.
- Migration is predictable based on residual styrene and exposure conditions.
- Temperature influences diffusion and partition coefficients linearly with their logarithms.