SUPERCRITICAL FLUID EXTRACTION AND CHROMATOGRAPHY FOR THE DETERMINATION OF OLIGOMERS IN POLY(ETHYLENE-TEREPHTHALATE) FILMS

Experimental dynamic supercritical fluid extraction and chromatography of lower oligomers from poly(ethylene terephthalate) films has been carried out both off-line and on-line. Quantitative results for kinetics of extraction of the cyclic ethylene terephthalate trimer have been obtained. Models for continuous (off-line) and discontinuous (on-line) extraction from films are developed and also a model for continuous extraction with nonuniform initial concentration distribution of extractable material across the film. The off-line experimental results compare satisfactorily with the models and indicate that only part of the cyclic trimer is extractable by a supercritical fluid and that the extractable material is distributed toward the surface. Discussion is made on the comparison with Soxhlet extraction and also as to why the on-line experimental results are not suitable for quantitative analysis.