Solvent Extraction Methods for NonFibrous Additives in Spun Yarns
Solvent extraction isolates spin finishes and waxes from spun yarns, preventing excess processing aids from inflating commercial mass and landed duty costs.
Polymer Swelling
Volumetric Expansion
Increase in the physical dimensions of a polymer mass caused by the absorption of a solvent or moisture into its molecular structure. During polymer swelling, the solvent molecules penetrate the intermolecular spaces and push the polymer chains apart. This action reduces the glass transition temperature and increases the flexibility of the material.
Dyeing Mechanism
Successful coloration of synthetic fibres often depends on the deliberate use of heat or chemical agents to induce this state. When polymer swelling occurs in a dye bath, it opens up the crystalline structure to allow large dye molecules to enter the interior of the fibre. Without this expansion, the dye would remain on the surface and wash away during the first laundry cycle.
The degree of expansion is monitored to prevent permanent loss of fibre strength. Finishers use specific carriers to accelerate this process in low-temperature environments.
Mechanical Impact
Dimensional stability in wet conditions is a direct result of how much a fibre expands. Fabrics that exhibit high levels of expansion can suffer from puckering at the seams or loss of shape.
Solubility Boundary
Expansion stops when the internal elastic forces of the polymer chains balance the chemical potential of the solvent. Excessive polymer swelling can lead to the total dissolution of the fibre if the solvent strength is too high.