Study of Optical and Structure Properties of Polyester (PET) and Copolyester (PETG) Fibers by Interferometry

In this article results on the influence of drawing on the optical and structure properties of polyester (polyethylene terephthalate) and copolyester (glycol-modified polyethylene terephthalate) (4 wt% of ethylene glycol) fibers are reported. Refractive indices, intrinsic birefringence, mean polarizability per unit volume, optical orientation function, density, volume fraction of crystalline material, weight fraction crystallinity, and volume fraction of amorphous and work per chain of these fibers have been evaluated at different draw ratios. A comparison of optical and structure parameters for copolyester fiber and referenced monopolyester fiber has been done. This study has been carried out by means of computerized double-refracting Pluta interference microscope combined with opto-mechanical devices. Microinterferograms and relationships between the parameters obtained are given for illustration.