Sorption and migration of organic liquids in poly(ethylene terephthalate)

Abstract

Abstract Sorption kinetics of organic liquids in amorphous poly(ethylene terephthalate) (APET) and biaxially oriented PET (BPET) were determined at 34°C. With heptane and 1,2 propanediol, no sorption or swelling was observed. Estimated diffusion coefficients based on analysis from pseudo‐Fickian sorption data are 3.7 ± 1.0 × 10 −9 cm 2 /sec for toluene sorption in APET, 12.7 ± 4.1 × 10 −9 cm 2 /sec for benzyl alcohol in APET, 0.44 ± 0.4 × 10 −9 cm 2 /sec for toluene in BPET, and 0.33 ± 0.4 × 10 −9 cm 2 /sec for benzyl alcohol in BPET. Weight gain of sorbed APET samples at equilibrium was 11.4 ± 0.1% in toluene and 21.7 ± 0.8% in benzyl alcohol. BPET weight gain at equilibrium was 9.5 ± 0.1% in toluene and 13.5 ± 0.2% in benzyl alcohol. Subsequent migration of sorbed toluene from APET samples into water at 34°C was measured by gas chromatography. Migration from toluene‐sorbed APET films sandwiched between virgin APET layers was two orders of magnitude less than from sorbed films placed directly in water.