ORIENTATION OF AMORPHOUS POLY(ETHYLENE-TEREPHTHALATE) BY TENSILE DRAWING, ROLL-DRAWING, AND DIE-DRAWING

Orientation of initially amorphous poly(ethylene terephthalate) films and sheets was carried out by means of tensile drawing in a tensile te ster, roll-drawing using a series of four rolling stations, and by die -drawing. The drawing temperature was 80 and 90 degrees C and drawing rate ranged from 2 to 20 cm/min in the different processes. Crystallin ity was observed to increase with draw ratio for all these processes. The onset of crystallinity development depends on the drawing rate. Th e glass transition temperature was essentially constant and crystalliz ation temperature decreased with increasing draw ratio. The trans conf ormers content was observed to increase with draw ratio at the expense of the gauche conformers for the three processes. The orientation of the trans conformers increases readily from the beginning of draw and saturates rapidly. The orientation of the gauche conformers was neglig ible. Some differences are observed for the behavior of the 1020 and 7 30 cm(-1) benzene ring bands, which may be due to differences in the b enzene ring configuration at the surface as a result of different defo rmation mechanisms for the die and roll-drawing. However, further inve stigations to elucidate this hypothesis are needed. The mechanical pro perties obtained in the longitudinal direction increased for all the p rocesses. In the transverse direction, the roll and die-drawing proces ses induced a decrease in modulus and strength with increasing draw ra tio, similar to that observed for uniaxial orientation. This indicates that these processes are mainly uniaxial, despite the plane strain na ture of the deformation.