The purpose of this study is to correlate surface properties of laundry detergents and model surfactant solutions with their washing abilities. For the study, laundry detergents available on the Polish market were selected and categorized according to their retail price: the cheapest (P1, P2, P3), average priced (P4, P5, P6, P7, P8) and the most expensive (P9, P10). Anionic sodium dodecylbenzenesulfonate and nonionic nonaethylene glycol monodecyl ether were used for the preparation of the model solutions. The content of the anionic and nonionic surfactants in the detergents was determined. Cotton fabrics were soiled with black carbon/olive oil, make-up, curry, red wine, tomato sauce, blood, chocolate, peat, tea, -carotene, grass, animal fat/red dye, baby food, clay, butter and used engine oil. Detergency tests were carried out at a temperature of 40 C in laboratory conditions using washing powders and model surfactant solutions in various concentrations. On the basis of the correlation between detergency and detergent properties, the most favorable size range of powder granules was identified. The negative correlation between contact angle, surface tension and detergency and the positive relationship between phosphorus pentoxide and active oxygen content, spreading coefficient, diffusion coefficient and detergency were determined. The closest correlation between surfactant content and detergency was observed at a concentration of 10 g/L, which resulted in maximum detergency. When the emulsifying properties were better, their soil removal efficiency was greater. Based on the analysis of the correlation, the characteristics of the tested laundry detergent solutions that had the greatest ability to remove dirt were described.
