AMORPHOUS STRUCTURE CHANGES IN POLY(ETHYLENE-TEREPHTHALATE) INDUCED BY ANNEALING UNDER DRY AND WET CONDITIONS AND ITS DYE UPTAKE PROPERTIES

The amorphous structure changes in poly(ethylene terephthalate) (PET) induced by annealing under dry and wet conditions were discussed in te rms of amorphous density (rho(a)) and dye uptake properties. The rho(a ) value of PET decreased with increasing annealing temperature, but it conversely increased at annealing temperatures above 210 degrees C fo r the dry treatment and above 170 degrees C for the wet treatment. Wit h decreasing rho(a) from 1.35 to 1.31 g cm(-3), the conformation of am orphous molecules changed from the gauche to trans form. The rho(a) va lue conversely increased on annealing at higher temperatures; however, the dye exhaustion continuously increased. The ratio of the absorbanc e of the alpha band to that of the beta band of the basic dye crystal violet (alpha/beta ratio), indicating the degree of dye aggregation, i n PET decreased with a decrease in rho(a). The degree of dye aggregati on further increased when rho(a) conversely increased on high temperat ure annealing. These results suggested that the free volume content of PET increased as a result of conformational change from the gauche to trans form in amorphous molecules with increasing annealing temperatu re, and finally the increased free volume converted to microvoids arou nd 1.31 g cm(-3) of rho(a). The dye exhaustion increased with increasi ng annealing temperature according to microvoid formation. (C) 1997 El sevier Science Ltd.