DEVELOPMENT OF A BIODEGRADABLE POLYMER COMPOSITION BASED ON CASEIN MILK

Abstract

The article sums up the results of the study of milk casein as a biopolymer, which is widely used in food industry, construction, pharmacy, etc. and on the basis of which polymer films for biodegradable materials can be obtained. The analysis draws on data on the structure of milk casein molecules as a complex globular micellar system, which is constructed by nanoscale sub-micelles, interconnected by calcium phosphate sites, with the formation of a casein-calcium phosphate complex. Sub-micelles differ in structure and function, according to which their four fractions are distinguished. The hydrophilic carboxyl groups of the glutamic, aspartic and orthophosphate acids of the κ-casein fraction provide the stabilization of casein micelles in the aqueous medium. Such structure of casein does not allow to receive film materials, they have low technological characteristics, very low durability and elasticity, high fragility. Moreover, they are easily soluble in water.
Studies have shown that on the basis of casein it is possible to obtain polymer films, provided the use of a polymer composition, in which besides casein there is a modified polysaccharide. To obtain such a composition, carboxymethylcellulose was used, which also has biodegradable properties, however, unlike casein, it is capable of forming sufficiently strong polymer films. The polymer composition was synthesized in two steps: first, an aqueous solution of carboxymethyl cellulose was prepared, to which freshly precipitated casein with a moisture content of 20%, precipitated from skim milk, was added. The composition of the polymer composition was enriched with a number of additives serving as plasticizers, and structure-forming. The triatomic alcohol glycerol and diphenylamine were added as plasticizers too. In order to regulate the structure of the aqueous dispersion medium and prevent the processes of aggregation of casein micelles, calcium chloride solution was injected in the composition. The given polymer composition after polymerization in the air-drying process makes it possible to obtain sufficiently strong composite polymer films, the transparency of which depends on the type of plasticizer selected and the presence of CaCl2.