Relation between Drawing Temperature and Critical Necking Tension on Zone-Drawing for Polyether Ether Ketone Films

The relation between the drawing temperature (Td) and the critical necking tension (σc) has been investigated in the Td range of 20°C to 280°C for unstretched amorphous polyether ether ketone films. The σc varied inversely with Td in the Td range of 20°C to 100°C. It was found that the temperature difference between Tg (143°C) and Td was proportional to σc. This relation is represented by the following equation: σc=0.055 (Tg-Td). The draw ratio, birefringence, and crystallinity were also measured for the zone-drawn films. The draw ratio and birefringence were almost independent of Td, and were 2.4 and 0.165, respectively. However, the cystallinity remained constant at 3.8% up to Td=100°C and then rapidly increased with a rise of Td. This suggests that the orientation cystallization takes place on zone-drawing above 110°C. Although the films zone-drawn below 100°C shrank up to about 60%, the film zone-drawn at 120°C shrank by only 4%, on heating in a silicone oil bath. The thermal shrinkage rapidly decreased also with increasing crystallinity. This relation between shrinkage and crystallinity suggests that the crystallites prevented the thermal motion of amorphous chains.