[en] The extraction process of the low molecular fraction from polethyleneterephthalate irradiated with heavy ions has been studied by its interaction with a series of solutions. It has been established that radiolysis products together with oligomers, formed in the tracks as a result of radiation-chemical properties, can be extracted from the irradiated polethyleneterephthalate. Results of this study show that the increase in the free volume, which causes an increase in the etchability of the tracks, occurs primarily as a result of the removal of the decay products from the polymer. 11 refs., 4 figs., 2 tabs