Stability kinetics of foam from aqueous solutions of polyvinyl alcohol with different molecular weight

The structure, foaming multiplicity and kinetics of foam stability from aqueous solutions of polyvinyl alcohol (PVA), as one of the main components of obtaining special-purpose filters have been studied. The dependencies of the foam stability coefficient of aqueous solutions of PVA on molecular weight and their concentration are given. It was established that with an increase in concentration of aqueous solutions of PVA, stability of foams increases, and when solution concentration is more than 8% (vol.), its stability is sufficient to produce special purpose filters. The most optimal molecular weight for producing stable foams from aqueous solutions of PVA is Mw = 68 000. The effect of surfactant on foaming multiplicity and the foam stability coefficient from aqueous PVA solutions was studied in solutions with constant molecular weight of PVA, Mw = 68 000 at two solution concentrations: 4 and 8% (vol.). It was found out that the optimal amount of surfactant to increase the stability of foams from aqueous solutions of PVA by ~3 times was ~1% (vol.). The foam structure was studied by optical microscopy. It was shown that with an increase in molecular weight from 22 000 to 81 000, the pore diameter decreased slightly (from 1.15 to 0.9 mm). A sharp decrease in the pore size (from 1.15 to 0.5 mm) is observed with an increase in concentration of aqueous PVA solution from 4 to 24% (vol.). For synthesis of porous filters and production of stable foams, it is recommended to use PVA with molecular weight of ~68000, 8% (vol.) aqueous solution of PVA with content of ~1.0% (vol.) surfactant in the solution, which provides sufficient foam stability during the period of the formation of filters.