Sorption kinetics of organic liquids In amorphous poly(ethylene terephthalate) (APET) and biaxially oriented PET (BPET) were determined at 34 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 toluene sorption in APET, 12.7 +/- 4.1 x 10(-9) cm(2)/sec for benzyl alcohol in APET, 0.44 +/- 0.4 x 10(-9) cm(2)/sec for toluene in BPET, and 0.33 +/- 0.4 x 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 degrees 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.