Chapter 8 - Overall orientation of textile fibers by sonic modulus and birefringence

Abstract

The dynamic modulus or sonic modulus is estimated using different methods by propagating sound waves through textile fibers at different strain levels. The maturity ratio and other parameters can be calculated by measuring the sonic modulus of cotton fibers. Sonic modulus and birefringence represent molecular chain orientation along the fiber axis in both amorphous and crystalline regions. Birefringence increases upon increasing the molecular chain orientation along the fiber axis. Birefringence of a textile fiber can be quantified directly by estimating the difference in optical path length or retardation in optical wave velocity. The optical path length is the multiplication product of fiber thickness through which the light transmits and the refractive index. In the case of a fiber that absorbs a considerable amount of water in its amorphous phase, the refractive index gets changed. In principle, the Herman’s orientation factor represents the average angle of molecular chains with the fiber axis in the crystalline region of semicrystalline fibers.