Microscopy Study of Distribution of Laundry Fabric Softener on Cotton Fabric

Abstract

AbstractDistribution of fabric softeners on cotton terry cloth was studied using scanning electron microscopy and energy dispersive X‐ray analysis. The unsaturated groups in the quaternary fabric softeners were tagged with osmium tetroxide to provide contrast in the microscopy. Longitudinal specimens showed the fabric softeners distributed over the cotton fiber surfaces with more in the crenulation of the fiber. Cross sectional specimens revealed that the fabric softener was distributed throughout the cotton fibers with higher concentrations of fabric softener observed in the lumen and crenulation than in the secondary wall and non‐crenulated fiber surface. This distribution of fabric softener is consistent with deposition on both external fiber surfaces and internal fibril surfaces. The deposition and final surface coverage is strongly dependent on the pH value of the washing medium. Repeated treatment cycles with fabric softener using a higher pH washing media resulted in higher concentrations of fabric softener on and within the cotton fibers. Neutral or lower pH washing media resulted in a somewhat constant concentration of fabric softener on and with cotton fibers with increased number of treatment cycles. Differences in perception of softness of the treated fabrics are not explained by differences in distribution of the fabric softener; it appear that there is an optimum amount of softener to achieve the desired sensory response and that further deposition build‐up does not increase perception of softness.