OPTO THERMAL-PROPERTIES OF FIBERS - IX - STUDY CHANGES OF OPTICAL-PARAMETERS BY MULTIPLE-BEAM TECHNIQUE DUE TO THERMAL ANNEALING FOR NATURAL SILK FIBERS

Multiple-beam Fizeau fringes were used for studying the effect of the annealing process on the refractive indices and birefringence of natur al silk fibers (best yellow Italian silk, Ford & Co. Ltd). Silk fibers were annealed at a constant time of 2 h with different annealing temp eratures ranging from 60 to 160 +/- 1 degrees C. A scanning electron m icroscope was used for measuring the cross-sectional shape and a longi tudinal view of the natural silk fibers. The Becke-line method was use d for measuring the skin refractive indices and the birefringence of t he natural silk fibers. The thermal coefficient of the refractive inde x, Cauchy dispersion constants, dispersive power, dielectric constant at infinity, polarizability per unit volume, isotropic polarizability, and isotropic refractive index were determined interferometrically. M icrointerferograms and curves are given for illustration. (C) 1998 Joh n Wiley & Sons, Inc. J Appl Polym Sci 69: 1495-1504, 1998.