Effects of drawing conditions on fiber structures and properties of PEEK filaments (Part 2). Structures and mechanical properties of peek filaments.

Abstract

Crystal orientation function, crystallite sizes and mechanical properties of drawn poly (ether ether ketone) (PEEK) filaments obtained by drawing amorphous unoriented filaments at temperatures from 20 to 280°C were investigated. The properties of filaments redrawn at 260 to 320°C after drawing at 145°C and 150°C (“two-step-drawn” filaments) were also examined. The degree of orientation increases with drawing temperature above 160°C and reached to the maximum value at 260°C. The maximum value of the crystal orientation function and the birefringence of amorphous region are 0.983 and 0.234, respectively. The largest value of tensile modulus of drawn filaments was 12.2GPa. Plots of amorphous compliance against birefringence of amorphous region showed a straight line, which have a large slope below the draw ratio of 2 and a small slope above the value of the draw ratio. The filaments redrawn at 260°C after drawing at 145°C showed almost the same values of the degree of crystallinity and orientation as the filaments drawn directly at 260°C. While the degree of orientation of amorphous region decreased with drawing temperature for the filaments drawing directly above 260°C, it increased up to 300°C for the “two-step-drawn” filaments. The number of crystallite in the filaments seems to affect the restriction of the amorphous regin.