Apparent Diffusion Coefficients for Reactive Dyes in Swollen Cellulosic Micro Capillaries
Apparent diffusion coefficients dictate internal fiber dye transport rate, governing shade levelness and fixation efficiency in swollen cellulosic processing.
Accessible Pore Volume
Internal Space
Total internal cavity space within a swollen cell wall determines the capacity of a substrate to absorb chemical finishes. The accessible pore volume dictates the maximum size of direct dye molecules or polymer precursor molecules that can penetrate the fiber matrix during wet processing. Larger molecular finishes require wider channels to achieve deep penetration.
Restricted networks limit chemical uptake to the fiber surface.
Measurement Protocol
Solute exclusion methods evaluate this characteristic by exposing wet fiber to a series of dextran polymer fractions of varying molecular weights. Low molecular weight fractions enter both large and small cavities easily. High molecular weight polymers remain excluded from the internal network entirely.
Measuring the change in concentration of the bulk solution yields the precise volume of the accessible channels.
Process Performance
Drying regimes exert a strong influence on the structure through irreversible pore collapse. This hornification process reduces the accessible pore volume during subsequent wetting cycles. Reclaiming the initial absorption capacity requires chemical swelling agents like sodium hydroxide to relax the hydrogen bonds.
Restored structural spaces allow uniform distribution of reactive dyes and finishing agents.
Boundary Limit
Mechanical constraints in tightly spun yarns prevent the complete expansion of individual fibers during the measurement phase. The actual chemical uptake in a commercial dye bath may fall below the laboratory values. Consequently, the calculated limit represents a theoretical potential rather than a guaranteed production yield.