Preparation and Regulation of Structural-Mechanical Properties of Biodegradable Films Based on Starch and Agar

The problem of recycling polymer waste is one of the most actual problems. One way to solve this problem is to create biodegradable food packaging. By mixing solutions of starch and agar at different mass ratios of polymers in the presence of glycerol, biodegradable films are obtained. Their structural and mechanical characteristics are determined. It is shown that the values of strength, modulus of elasticity and puncture resistance of films are maximal at the mass ratio of agar/starch 7-9. A comparison of the roughness of the films obtained from starch, agar and their mixture showed that the greatest roughness is possessed by films based on starch. The introduction of agar into the films of starch leads to a significant reduction in their roughness. To regulate the structural and mechanical properties of films, it is proposed to use Cа and Mg salts. The influence of Ca 2+ and Mg 2+ ions on the strength and deformation characteristics of biofilms was studied. It is shown that Ca 2+ ions monotonically increase the strength characteristics of starch-agar films, while the curves of changes in these parameters in the presence of Mg 2+ ions have maxima at a concentration of 0.5 %. The difference in the effect of Ca 2+ and Mg 2+ ions on the structural and mechanical properties of films is explained by the hydration degree of these ions. The biodegradability of starch-agar films was controlled by changing their IR spectra. The most significant changes are observed in the intensity and localization of peaks corresponding to O-H, C-H and C-C bonds, which can be evidence of changes in the structure of films due to the destruction of the grid of hydrogen bonds and hydrophobic interactions, as well as the break of hydrocarbon chains and the destruction of the skeleton of carbohydrate molecules.