Aging of oily soils on textiles. Chemical changes upon oxidation and interaction with textile fibers

Abstract Aging of unsaturated oily soils on textile materials produces yellow compounds that are difficult to remove by washing. To investigate changes that occur in oily soils when aged, the aging of squalene and artificial sebum were studied. Proton nuclear magnetic resonance, infrated spectroscopy, gas chromatography, and gel permeation chromatography studies showed that oily soils were oxidized upon aging, forming low molecular weight products that also polymerized to higher molecular weight compounds with prolonged aging. The oxidation products contained hydroxyl, carbonyl, or ester groups. Oxidation compounds with yellow chromophores appeared to be mostly those of the 1000–2500 molecular weight fraction; though in earlier, stages of aging, lower molecular weight fractions also contained chromophores. By using glucose as a model compound of cellulose, it was found that yellow oxidation products of aged squalene were covalently bound to the substrate. Because the aging of oily soils is a free‐radical oxidation process, oxidation products having chromophores are thought to attach to the cotton substrate through radical coupling. Oily soils also showed possibilities of chemical bonding with nylon but not with polyester.