Opto-mechanical properties of fibres. Part 2. Effect of stretching on some optical and structure parameters of PET fibres (Woollen type)

The influence of cold drawing on the birefringence, orientation, crystallinity and other structural parameters is examined for polyester (Egyptian PET woollen type). A two-beam Pluta polarizing interference microscope connected to a device for dynamically studying the effect of the draw ratio on the refractive indices has been used. The optical data obtained the densities and crystallinities of the samples. The mean square density fluctuation [eta(2)], crystalline orientation function, amorphous orientation function, the number of chains per unit volume N-c and the number of random links between the network junction points N-1 are then calculated. Calculations are also carried out to determine the strain optical coefficient, the orientation factor, the orientations angle, the number of molecules per unit volume N, and the isotropic refractive index. In addition, Poisson's ratio over all strain ranges, the distribution of segment at an angle theta with respect to the draw ratio, the electric polarizability constant (Delta alpha/3 alpha(o)) and other structural parameters and constants are calculated. An empirical formula is suggested to correlate the change in Delta n, F-o, F-a, omega(cos theta), A and N-c, and its constants are determined. The refractive index profile is studied. Interferograms and curves are given for illustration. (C) 1999 Society of Chemical Industry.