Kinetics of Stability of Foams from Aqueous Solutions of Polyvinyl Alcohol with Different Molecular Weight

The structure, expansion ratio, and kinetics of stability of foams from aqueous solutions of polyvinyl alcohol (PVA) as a one of the main components to produce special-purpose filters were studied. The stability factors of foams from aqueous solutions of PVA are given as a function of the PVA molecular weight and the solution concentration. It was found that the foam stability increases with an increase in the concentration of aqueous solutions of PVA and, at a solution concentration of more than 8 vol %, is sufficient to produce special-purpose filters. The molecular weight M w = 68 000 is the most optimum for producing stable foams from aqueous solutions of PVA. The effect of a surfactant on the expansion ratio and stability factor of foams from aqueous solutions of PVA was studied on solutions with constant molecular weight of PVA M w = 68 000 at two solution concentrations of 4 and 8 vol %. The optimum amount of the surfactant to increase threefold the stability of foams from aqueous solutions of PVA was found to be about 1 vol %. The foam structure was studied using optical microscopy. The pore diameter was shown to insignificantly decrease (from 1.15 to 0.9 mm) upon an increase in the molecular weight from 22 000 to 81 000. A dramatic decrease in the pore size (from 1.15 to 0.5 mm) was observed upon an increase in the concentration of an aqueous solution of PVA from 4 to 24 vol %. An 8 vol % aqueous solution of PVA with a molecular weight of ~68 000 containing ~1.0 vol % of surfactant, providing a sufficient foam stability with time for molding of filters, is recommended for the synthesis of porous filters and the production of stable foams.