SORPTION AND MIGRATION OF ORGANIC LIQUIDS IN POLY(ETHYLENE-TEREPHTHALATE)

Sorption kinetics of organic liquids In amorphous poly(ethylene tereph thalate) (APET) and biaxially oriented PET (BPET) were determined at 3 4 degrees 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 x 10(-9) cm(2)/sec for t oluene sorption in APET, 12.7 +/- 4.1 x 10(-9) cm(2)/sec for benzyl al cohol in APET, 0.44 +/- 0.4 x 10(-9) cm(2)/sec for toluene in BPET, an d 0.33 +/- 0.4 x 10(-9) cm(2)/sec for benzyl alcohol in BPET. Weight g ain 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. Subse quent migration of sorbed toluene from APET samples into water at 34 d egrees C was measured by gas chromatography. Migration from toluene-so rbed APET films sandwiched between virgin APET layers was two orders o f magnitude less than from sorbed films placed directly in water.