Opto-thermal properties of fibres. Part 2: Investigation of optical parameter changes in annealed and quenched nylon 6-6
The changes in refractive indices and birefringence of nylon 6-6 fibres with different annealing conditions were studied by interferometry. The polarizing interference microscope was used to determine the mean refractive indices and mean birefringence of these fibres. Also, an acoustic method has been used to measure densities. The results are used to calculate some structural parameters such as the form birefringence, virtual refractive index, harmonic mean polarisability of the dielectric, and the specific refractivity of the isotropic dielectric. Also, the number of monomer units per unit volume and the refractive indices of fully oriented fibre, when using monochromatic light vibrating parallel and perpendicular to the fibre axis, were calculated and found to be 1.5543 and 1.4723. The generalized Lorentz-Lorenz equation given by de Vries was used to determine nylon 6-6 fibre structural parameters. Comparisons between Herman's optical orientation function formula and the corrected formula by de Vries are given.