T. Wodka et al., Studies of the process and properties of additionally polycondensed co-polyethylene (terephthalate-isophthalate) in a solid phase, FIBRES TEXT, 8(1), 2000, pp. 41-44
A run of an additional polycondensation process of co-polyethylene(terephth
alate-isophthalate) in a solid phase was investigated at a temperature of c
a. 230 degrees C during 7-13 hours by evaluating changes in the properties
of this polymer i.e., molecular weight, intrinsic viscosity, acetic aldehyd
e content and carboxyl groups content, melt temperature, crystallinity degr
ee, and polydispersity degree. It was found that the initial polymer formed
during a liquid phase and having a molecular weight of ca. 16500 increases
in weight after its additional polycondensation in a solid phase, even up
to eel 28000. Simultaneously, the content of acetic aldehyde in the polymer
decreases from 150 ppm (initial polymer) to 2.3 ppm (after additional poly
condensation). It was found at the same time that such a decrease in acetic
aldehyde content in the polymer takes place already during the initial pro
cess of polymer during and its crystallisation, and that the changes in its
content during additional polycondensation are inconsiderable. Moreover, a
distinct decrease in polydispersity degree in the case of an additionally
polycondensed polymer was confirmed.