Drawing mechanism of peek filaments - Effects of drawing temperature and draw ratio.

Abstract

Drawing mechanisms are described for poly (ether-ether-ketone) (PEEK). Unoriented amorphous PEEK filaments were drawn at -115 to 300°C, and the effects of drawing temperature and draw ratio to the crystallinity and the molecular orientation of resulting filaments were analyzed. The elongation at break increased at about -100°C and -20_??_40°C. It also showed sharp peak at Tg. Then so-called super-draw was not observed. These temperatures corresponded to the mechanical relaxation peaks. The drastic drop of elongation above Tg was caused by crystallization in drawing process. The density of drawn filaments also decreased and showed minimum at 160 to 180°C. These results indicate microvoid formation in drawing. Above 280°C. drawn filaments became unhomogenous, while homogenous filaments were obtained at 300°C by drawing previously at 145°C. Above 0°C, density of filaments increased in drawing, nevertheless the crystallization was not observed below 140°C. It was caused by enthalpy relaxation with rearrangement of chain conformation. The birefringence of drawn filaments was almost independent of drawing temperature at -74_??_150°C. When the draw ratio was up to 1.5 times, molecular orientation could be approximated by rubber elasticity and no density change was observed. On the other hand, drawing behavior could be described by pseudoaffine model and the density increased in drawing at ratios more than 2 times.