Journal of Applied Polymer Science, Vol.77, No.9, 2044-2048, 2000
Conditions of homogeneous deformation of poly(ethylene terephthalate) films during uniaxially drawing
Amorphous poly(ethylene terephthalate) film was uniaxially drawn over a wide range of temperatures from below to above the T-g at a constant strain rate. The geometry of the deformation in macroscopic dimensions of the sample demonstrates that homogeneous deformation can be obtained when the drawing temperature (T-def) is not lower than 69 degrees C. The change of the cold crystallization peak temperature (T-cc) and crystallinity determined by differential scanning calorimetry and density measurement, respectively, were studied in terms of the T-def and the draw ratio (lambda). The orientation, relaxation, and crystallization during drawing were investigated as a function of T-def as well as of lambda. The results suggest that 69 degrees C is the critical temperature at which the sample with the highest orientation and the least slippage of the molecular chain and without obvious crystallization can be obtained.