Dimensional Expansion
Rate at which textile filaments expand in diameter upon exposure to moisture or chemical agents. The study of yarn swelling kinetics allows engineers to predict how a fabric will behave during wet processing stages such as mercerization or dyeing. Fibres like cotton or viscose show immediate diameter increases when they absorb water molecules into their regions.
This change affects the overall porosity of the textile web.
Reaction Rate
Speed of the expansion depends on the temperature and the concentration of the liquid medium. Most yarn swelling kinetics measurements occur in the first few seconds of immersion.
Mechanical Consequence
Pressure increases within the yarn structure as the individual fibres push against each other during the swelling phase. This internal force can lead to changes in the tensile strength and the elasticity of the material. In tightly woven fabrics, the expansion of the yarns reduces the space between the interlacing points.
This restriction often results in the stiffening of the fabric hand and a reduction in the drape quality. High swelling rates can also lead to the permanent deformation of the yarn geometry if the material is held under tension.
External Influence
Finishers control the swelling by adding salts or adjusting the pH of the bath. Proper management of yarn swelling kinetics ensures uniform dye penetration across the entire cross section of the yarn.
