MECHANICAL-BEHAVIOR OF POLY(ETHYLENE 2,6-NAPHTHALENE-DICARBOXYLATE) (PEN) FIBERS NEAR THE GLASS-RUBBER TRANSITION-TEMPERATURE

The mechanical properties of as-spun poly(ethylene 2,6-naphthalene-dic arboxylate) (PEN) fibres were studied in order to characterize this re latively new material near its glass-rubber transition. Tensile tests were carried out on amorphous (low-speed spun) PEN filaments. The temp erature range of 90-degrees-C up to 160-degrees-C was covered using in crements of 10-degrees-C. A transition from necking and cold drawing t o rubber-like behavior was observed in the stress-strain relationship. Dynamic mechanical experiments were carried out on PEN yarns spun at speeds from 500 to 4000 m min-1. Both temperature and frequency were v aried. The maxima in loss modulus depend on spinning speed. Tensile be havior and dynamic mechanical behavior of PEN fibres demonstrate that the glass-rubber transition temperature of PEN is approximately 125-de grees-C.