The effect of glycerol and boric acid on the properties and destruction of biodegradable cryogels
M. S. FUFAEVA1, V. S. OVSYANNIKOVA1, S. E. DRAGULA1, A. S. BUYAKOV2
1Institute of Petroleum Chemistry, Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
2Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
Keywords: polyvinyl alcohol, potato starch, boric acid, glycerol, cryogel, elasticity, biodegradation, ecology
Abstract
The influence of glycerol and boric acid on the rheological properties of aqueous solutions of polyvinyl alcohol (PVA) and starch, as well as on the elastic and thermophysical properties of cryogels prepared from them, was studied. It has been shown that all solutions exhibit non-Newtonian properties. The addition of 0.5 wt% boric acid caused an increase in the dynamic viscosity of PVA solution by a factor of 1.5-2.3, and starch solution by a factor of 0.8-1.1; the addition of 0.25 wt% boric acid with 10 wt% glycerol as a plasticiser caused a 1.6-2.4 times increase in the viscosity of PVA solution, and the viscosity of starch solution increased by a factor of 0.9-1.3. The addition of 20 wt% plasticiser (glycerol) had a maximum effect and caused an increase in the dynamic viscosity of PVA solution by a factor of 1.8-2.6, and starch solution by a factor of 1.1-1.5. It has been determined that the elastic modulus of cryogels increases with the addition of glycerol and boric acid into the polymer solution (PVA, starch or their mixture). The elastic modulus of cryogels has been determined to depend primarily on the proportion of each polymer in the mixture, and then on glycerol concentration, increasing by a factor of 2.6-12 in its presence. During destruction in water, the mass loss by compositions based on starch was 45-70 % within 20 days. For the mixed compositions with two polymers, the weight loss within 30 days varied within the range of 40-65 %. The presence of glycerol suppressed the destruction of samples with high PVA content (weight loss 24-28 %) and stimulated the decomposition of cryogels with high starch content (weight loss up to 83-87 %). Microstructural studies of films based on PVA and starch with glycerol before and after biodegradation showed the colonisation of surfaces by microbial cells, the appearance of irregularities, cracks and cavities.
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