Electron Microscopical Analysis. of Oily Soil Penetration into Cotton and Polyester/Cotton Fabrics

A method was developed for microscopical analysis of oily soils on fiber surfaces and in the fiber structure. Triolein, an unsaturated triglyceride which is a dominant consituent of human sebum, was applied to cotton and polyester/cotton fabrics with durable press finishes. Osmium tetroxide was used to label the triolein by reaction with the double bond. Backscattered electron imaging and electron beam X-ray microanalyses were used to study the location of the oil in the interfiber capillaries within yarns and in the fiber structure after 5, 10, and 15 soil-age-wash cycles.

Large amounts of residual triolein accumulated in the interfiber capillaries within the yarns. Cotton fibers also entrapped oil in the crevices of fibers that had bean- shaped cross sections and in the lumen. Retention of oily soil by cotton fibers was thus highly dependent on fiber maturity. For polyester fibers, no triolein was ob served in the interior region of the fiber, although there were large quantities of residual oil on the fiber surfaces.

A powdered detergent containing carbonate and zeolite builders cleaned fiber surfaces better than an unbuilt, liquid laundry detergent. Less residual triolein remained in the interfiber capillaries of cotton fabrics after laundry treatments using longer wash time, increased mechanical action, and a higher concentration of detergent. Treating with a prewash product containing an organic solvent re moved oil from the interfiber capillaries and the crevices of the cotton fibers. Oil in the lumen of the cotton fibers was partially removed by a prewash product followed by laundering, and completely removed by extraction with an organic solvent.