Preparation and Properties of Biodegradable Cryogels Based on Polyvinyl Alcohol and Potato Starch for Use in Soil Erosion Control

Compositions for the formation of three-component elastic cryogels based on the aqueous solutions of polyvinyl alcohol (PVA) and potato starch are proposed. It is shown that the viscosity of aqueous solutions depends both on the kind of polymer and on the total content of polymers in the system. The elasticity modulus of threecomponent cryogels depends on the concentration of starch in them and increases from 5 to 15 kPa with the addition of starch in the amount of 1-5 wt. %. By introducing a dispersed material (soil) into the matrix of twoand three-component cryogels, due to the high adhesion of the polymer to the filler, the filled cryogels were obtained, with the elasticity modulus 16 times higher than that of cryogels without the filler. The introduction of potato starch in the amount of 5 wt. % into PVA cryogel caused an increase in the time of its complete drying by 24 h, and an increase in its destruction during exposure in water by 5% within a week. Two-component cryogels exhibited sharply different types of behaviour during storage in water: PVA cryogel did not lose its mass, while mass loss by the cryogel of potato starch was 11% within a week. A decrease in the mass of three-component cryogels by 75-89% due to the loss of moisture and destruction was demonstrated in the soil test under the action of aboriginal soil microflora. The mass loss by the two-component cryogel based on PVA was 60%. Soil testing for phytotoxicity after the destruction of three-component cryogels revealed a decrease in the germination capacity of white mustard (Sinapis alba L.) by 2-10% with respect to the reference experiment, depending on starch content, while for the reference two-component PVA cryogel the corresponding decrease was by 18%. Cryostructuring of the upper soil layer by PVA cryogel caused an increase in the dry above-ground mass of plants by 3.2% in comparison with the reference, while the cryogel with potato starch caused an increase by 7.1%, and cryogel based on PVA and potato starch gave 9.4%.