Strain-Induced Crystallization in Uniaxially Drawn PETG Plates

摘要

The copolyester poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG) is used industrially as an uncrystallizable polymer, whereas PET is an inherently crystallizable polymer. Nevertheless, a crystalline phase could appear in the material. To create a strain-induced crystalline phase in an initially amorphous PETG material, plates were placed in the heating chamber of a tensile machine at 100deg C and uniaxially drawn to obtain different samples with various draw ratios. During DSC analysis of highly drawn samples, perturbations of the baseline appear above the glass-transition temperature, consisting of weak exothermic and endothermic phenomena. Comparison of DSC and X-ray diffraction analysis of drawn PETG and PET shows that a strain-induced crystalline phase appears in this copolyester. A spherclitic superstructure could also appear after lengthy annealing. Analysis of this semicrystalline material allowed estimation of the degree of crystallinity, about 3% after a drawing at high draw ratio and about 11% for undrawn annealed material.