AMORPHOUS PHASE ORIENTATION IN BIAXIALLY DRAWN POLY(ETHYLENE-TEREPHTHALATE) FILMS

An experimental study of the development of molecular orientation in t he amorphous phase during the transverse drawing of one-way drawn poly (ethylene terephthalate) films has been carried out. Both the behaviou rs of phenyl ring normals or chain axes and of fluorescent rigid probe s have been considered. The influence of the size of the crystallites in the one-way drawn films has been studied. It is first shown that th e phenyl ring normals in the amorphous phase tend to become more perpe ndicular to the draw direction, as expected. However, there is no mark ed tendency for the rings to lie in the plane of the film, on the cont rary with the crystalline phase. The chain axes, as well as the fluore scent probes, tend to align along the second draw direction. In films possessing initially long crystals, this reorientation appears less ef ficient at equivalent draw ratios. A memory of the state of the amorph ous orientation in the one-way drawn films is observed in the sense th at more relaxed one-way drawn films will lead to broader distributions in the final biaxially stretched films. (C) 1997 Science Ltd.