Chemical changes in oily soils upon aging and their interaction with textile fibers.

摘要

The aging of unsaturated oily soils on textile materials produces yellow compounds that are difficult to remove by washing. To investigate the changes that occur in oily soils when aged, the aging of squalene and artificial sebum were studied. {dollar}sp1{dollar}H-NMR, IR spectroscopy, GC and GPC studies showed that the oily soils were oxidized upon aging, forming low m.w. products that polymerized into higher m.w. compounds with prolonged aging. The oxidation products contained hydroxyl, carbonyl or ester groups. Compounds with yellow chromophores appeared to be mostly those of the 1000 {dollar}sim{dollar} 2500 molecular weight fraction, though in earlier stages of aging, lower molecular weight fractions also seemed to carry chromophores.; By using glucose as a model compound of cellulose, it was found that yellow products of aged squalene covalently bond to the substrate. Since the aging of oily soils is a free-radical oxidation process, oxidation products carrying chromophores are thought to attach to the substrate through radical coupling or through a reaction between the alcohol groups of cellulose and ketones of aged oils resulting in hemiketals. Oily soils also showed possibilities of chemical bonding with nylon but not with polyester. By quantitatively measuring color changes and soil removal upon aging and washing of soiled cotton, nylon and polyester fabrics, it was found that aging of the oils enhanced the oil removal upon washing; however, residual yellow compounds remained. Aged oils were most difficult to remove from cotton, but color removal was most difficult from nylon.; IR spectroscopy and GPC of used motor oil showed that the oil was a saturated aliphatic hydrocarbon with molecular weight around 950. X-ray analysis revealed that particulates present in the oil contained S, Mg, Al, Si, K, Ca, Fe, Ni, Pb, Cu and Zn. Used motor oil was more uniformly distributed within cotton fibers, with higher oil concentrations within the secondary cell walls compared to that of sebum. Dispersant additives of motor oil are thought to enhance penetration into the cotton structure and wicking over the polyester fibers making used motor oil very difficult to remove by detergency.