The twist moment and energy in twisting of a nylon 6 monofilament were measured at different temperatures. The filament was twisted as high as 80% of the breaking twist. The twisting moment and energy decreased with increasing temperature, particularly above 140°C.
The analysis of the twist moment under different rates of twisting by an Eyring theory gave 32 kcal/mol and 47 kcal/mol as the activation energy below and above 140°C respectively. In order to discuss the difference of the deformation behaviours between twisting and constant rate extension, the stress-strain relation in extension was also measured. Although the stress decreased with increasing temperature, the temperature dependence was less in extension than in twisting.
The difference was also remarkable in the energy recovery ratio, i.e. the ratio decreased slightly above 140°C in twisting, while it increased monotonously in the constant rate extension.
A composite master curve was obtained from the relaxation curves of twist moment at different temperatures. The shift factor was described by an Arrhenius relation, with a deflection point at 140°C. The activation energies from the relaxation data were very close to these from Eyring analysis.
The thermal expansion of the crystal was measured by wide angle x-ray diffraction with the result that the expansion coefficient of the
c* spacing increases above 140°C. The result indicates that the change in the deformation behaviours observed both in twisting and extension at about 140°C is attributed to the plastic deformability of crystals.
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