Amorphous films of poly(ethylene 2,6-naphthalate) (PEN) were drawn isothermally at temperatures between 1308C and 1608C, more specially at 1458C up to the desired draw ratios, mainly to study structure formation during uniaxial drawing by differential scanning calorimetry. During drawing, a rigid phase structure was induced and the results were analyzed in comparison with stress–strain curves in order to relate the amount of induced rigid phase structure at the earlier-mentioned temperatures with the observed stretching behaviour. During the uniaxial drawing of PEN at temperatures between 1308C and 1608C, the amount of amorphous phase was linearly related to the square root of the extra first strain invariant. The stress–strain curves were characterized by a necking behaviour and the end of the yielding or necking was reached when the amount of induced rigid phase attained 50%. The rigid phase then acted as the continuous phase and the stress increased very strongly. The stretching behaviour of PEN was characterized more by the strain induced rigid phase formation than by the stress or strain induced crystallization.
Посилання на статтю:
Relationship between stress and orientation induced structures during uniaxial drawing of poly(ethylene 2,6-naphthalate) / G. Schoukens // Polymer. – 1999. – N 40. – P. 5637–5645.