SynopsisThe diffusion of C.I. Disperse Violet 1 and Violet 8 in poly(ethy1ene terephthalate) (PET) WBB investigated by the method of cylindrical film roll. The effect of tetrachloroethylene (TCE) on the properties of PET was also studied. The treatment of PET with TCE brought about a strong effect on the thermal properties without degradation of PET. The diffusion of disperse dyes in PET from the TCE dyebath was faster than that from the aqueous dyebath. The activation energies of diffusion in the temperature range of 60' to 95OC from the TCE dyebath were smaller than those from the aqueous dyebath. Some break points were observed in the Arrhenius plots of diffusion coefficients in PET from the TCE dyebath. They were lower than those observed a t dry and water-swollen states.