Crystallization of poly(diethylene glycol terephthalate)

The crystallization of a low molecular weight fraction of poly(diethylene glycol terephthalate) (PDET) was studied from the melt and from benzene, ethyl acetate and chlorobenzene. From the melt, crystallization does not occur, irrespective of the crystallization temperature. When PDET is crystallized from solutions in the three solvents, by isothermal growth at temperatures from 10 to 30°, crystals are obtained in the concentration range examined. Crystals were investigated by X-ray diffraction and by differential scanning calorimetry in order to measure the crystallinity, the melting points, glass transition and melting depression of mixtures of the polymer with solvents. Prior to crystallization, at given undercoolings and sufficient concentrations, gelation occurs due to microstructural heterogeneity.