OPTOTHERMAL PROPERTIES OF FIBERS .2. STRUCTURAL CHARACTERISTICS OF COLD DRAWN ANNEALED EGYPTIAN POLYESTER (PET) FIBERS

Egyptian poly(ethyleneterephthalate) (PET) fibers in the drawn state s how considerable optical and mechanical anisotropy. The polarizing int erference microscope is used with a fiber manipulation device to study , dynamically, the variation of refractive indices and birefringence o f PET fibers with the draw ratio. In addition, the resulting data were used to calculate the strain optical coefficient, Poisson's ratio, th e mean square density fluctuation under different annealing conditions , as well as several other parameters and constants. Also, an empirica l formula has been applied to demonstrate the variation of the cross-s ectional area of PET fibers with draw ratio and the constants of this formula are determined Microinterferograms are given for illustration. The change of refractive index profile of annealed PET fibers at diff erent conditions are also shown. (C) 1997 Elsevier Science Ltd.