Studies of the process and properties of additionally polycondensed co-polyethylene (terephthalate-isophthalate) in a solid phase

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.