Strain‐induced crystallization in uniaxially drawn PETG plates

Abstract

ABSTRACT: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 100°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 spherulitic 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.

Effects of thermoforming on the physical and mechanical properties of thermoplastic materials for transparent orthodontic aligners

“…This finding is inconsistent with that in a previous study showing an increase in transparency with a decrease in thickness 28. In another study, however, the transparency of thermoplastic plates that deformed from amorphous to crystalline structures decreased according to the temperature, pressure, and working time, while light was scattered by the thermoplastic materials after thermoforming 29. Therefore, structural deformation of thermoplastic materials results in decreased transparency.…”

Preparation and characterization of thermoplastic materials for invisible orthodontics

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Finite strain behavior of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate)-glycol (PETG)

“…Recent work by Kattan, et al [38] addressed the difference in crystallizability between the two polymers. They conducted uniaxial tension experiments on both materials at a strain rate of 0.14 s K1 and a temperature of 95 8C.…”