Reaction Ratio
Quantitative relationships govern the molecular ratio of a chemical swelling agent to the polymer repeat units during fiber treatment. In textile finishing, swelling stoichiometry determines the number of sodium hydroxide molecules associated with each anhydroglucose unit of cotton cellulose during mercerisation. This ratio directly influences the extent of crystalline transformation and the final fiber properties.
Processing Impact
The maximum swell of cotton fibers occurs at a specific concentration and temperature of the alkali bath, where the hydrate structure matches the swelling stoichiometry. If the concentration deviates from this optimum, the swelling is incomplete, and the fabric does not achieve the desired luster or dye affinity. This behavior requires precise control of the caustic soda concentration.
Structural Changes
During the swelling process, the crystal lattice of cellulose I expands to accommodate the solvent molecules and ions. This expansion allows the subsequent conversion to the cellulose II structure during the rinsing and neutralization stages. The mechanical strength of the wet fabric depends heavily on how uniformly this transition occurs across the fiber cross-section.
Process Monitoring
Textile mills analyze the barium activity number to evaluate the uniformity of the treatment. A high, consistent number indicates that the optimal chemical ratio was achieved throughout the fabric.
