Quantifying Radial Fixation Gradients in Ultra High Twist Viscose Ply Yarns under Dynamic Alkali Steaming
Dense viscose ply yarns require controlled swelling alkali blends to eliminate core fixation gradients during dynamic steam fixation.
Fiber Swelling Factor
Dimensional Metric
Physical expansion measurements quantify the dimensional changes of cellulosics and synthetics when exposed to aqueous liquids or chemical reagents. The fiber swelling factor expresses the ratio of swollen fiber cross sectional area or diameter to dry fiber dimensions. Mercerization of cotton drastically alters this ratio by converting cellulose I to cellulose II crystal structures.
Microscopic image analysis or liquid displacement techniques measure the volumetric shift during saturation.
Sorptive Mechanics
Water molecules penetrate amorphous regions of hydrophilic fibers, pushing adjacent polymer chains apart and expanding the cross section. Synthetic fibers experience minimal swelling in water due to high crystallinity and hydrophobic functional groups. Chemical agents like caustic soda disrupt hydrogen bonding in cotton, forcing rapid lateral expansion while longitudinal length decreases.
Fiber swelling factor values increase proportionally with liquor temperature up to structural saturation points.
Process Consequence
Increased fiber dimensions reduce pore volume between adjacent yarns in tight woven fabric constructions. Liquid transport slows as capillary channels constrict under high volumetric expansion. Dye liquor penetration improves within individual fibers because expanded amorphous regions allow larger dye molecules to diffuse into internal active sites.
Laboratory Protocol
Gravimetric and optical protocols measure wet and dry fiber dimensions under controlled atmospheric humidity. Standardized procedures require constant temperature baths during measurement.