Opto-thermal properties of fibers XVIII - Skin-core structures variations in nylon 6 fibers due to different annealing conditions

Nylon 6 fibers (Amilan) were annealed at constant temperature 140 +/- 1 deg reesC for different time durations (1-10 h). Refractive indices have been p reviously measured interferometerically. Two independent techniques were us ed to study the optical an isotropy and density in these fibers. The first was the application of a multiple-beam to determine the skin and core "mean " refractive indices and birefringence of the samples. The technique used m ultiple-beam Fizeau fringes in transmission. The second technique was an ac oustic method for measuring the density of the investigated fibers. The opt ical results were used to calculate the optical orientation factors for ski n and core. The values of (Delta alpha /3 alpha (0)), which depend upon the molecular structure of the polymer, remain constant and in agreement with the previous published data. The density results were used to calculate the degree of crystallinity of nylon 6 fibers. In addition, the results were u sed to calculate the mean square density fluctuation, the harmonic mean pol arizability of the dielectric, specific refractivity of the isotropic diele ctric and the virtual refractive index. Also, the number of monomer units p er unit volume, and n(1) and n(2), which are the refractive indices of full y oriented fiber, were calculated and found to be (1.606 and 1.534). Herman s optical orientation functions have been compared with the generalized Lor entz-Lorenz equation given by de Vries. Microinterferograms and curves are given for illustration. (C) 2001 John Wiley & Sons, Inc.