Changing the Contact Wetting Angles when Adding Surface-Active Substances to Washing Solutions

Introduction. The technological processes of the washing contaminations are largely determined by the nature of the surface being cleaned, the contamination type and the environment, in which the cleaning is carried out. The efficiency of the process depends on the contact of the detergent with the surface being washed. The wetting characteristic is a contact angle, which is a measure of the relative attraction of a liquid to a solid and to liquid itself. The physico-chemical activity of the washing medium determines the costs and, consequently, the optimal parameters of the washing process. In addition, it affects the increase in corrosion resistance. Therefore, it is relevant to determine the functional dependence of the contact wetting angle on the concentration of various combinations of surfactants. Materials and Methods.The determination of the contact wetting angle is based on the statistical processing of a photograph of a detergent drop on a horizontal surface by a specially created program that allows obtaining an array of data to describe the shape of a drop from which the contact wetting angle is calculated. The values of the contact wetting angle were measured when varying concentrations of such synthetic detergents as Labomid-203, MS-8, ML-51, etc. Multiplicative power functions connecting the magnitude of the contact wetting angle with surfactant concentrations were obtained. Results. The studies has shown that an increase in the concentration of potassium monoborate with Labomid-203 by 1 % leads to a decrease in the contact wetting angle by 0.54 %; potassium monoborate with MS-8 by 0.78 %; and potassium monoborate with ML-51 by 0.48 %, the function shows a decreasing return to an increase in concentration. Discussion and Conclusion. In all the considered cases, a decreasing return of the magnitude of the contact wetting angle to an increase in the concentration of surfactants was established, regardless of which combination of substances was used. That is, the investigated concentrations of surfactants exceeded the limit value when they gave an increasing return to the increase in their content in the washing solution. Thus, it can be concluded that for the considered combinations the percentage of surfactant is redundant.