The Measurement of Molecular Orientation in Polyethylene Terephthalate Filaments by X-Ray Diffraction

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Abstract
An x-ray method has been developed to measure the over-all crystalline orientation in polyethylene terephthalate fibers. Coupled with optical birefringence studies which measure total orientation, it allows an estimate to be made of the noncrystalline orienta tion. It has been shown, for yarns drawn under the same conditions as these fibers. that it is the noncrystalline orientation which changes with draw ratio, the crystalline orientation remaining approximately constant with draw ratio and heat treatment. The results are also discussed in rotation to the theories on strain-induced crystalli zation in drawn polyethylene terephthalate fibers. 1 Palmer, R. P., I.C.I. (Plastics Division), unpublished work. 2 Knapp, P. E., I.C.I. (Fibres Division) unpublished work. 3 Howells, E. R., I.C.I. (Plastics Division), unpublished work.