Improving the Biodegradability and Mechanical Strength of Corn Starch-LDPE Blends through Formulation Modification.

Six corn starch-LOPE film blends containing starch in the range 5-40 % by weight, oleic acid as a Lewis catalyst with concentration of either 5 % or 10 %, maleic anhydride as a coupling agenl with concentration of either 2 % or 10 % and benzoyl peroxide as free radical initiator with concentration of either 0.1 % or 0.25 % were prepared. Fungal growth tests (ASTM G21) using Penicillium funiculosum were carried out on the samples made according to the above formulations. Tensile tests (ASTM 0638) and SEM imaging were also carried out on the samples before and after incubalion with Penicillium funiculosum for three weeks. The results of ASTM G21 test and SEM imaging showed that the increase in starch content from 5 % to 40 % in the formulations containing all three additive increases the biodegradability of the samples whereas increase in the concentration of oleic acid from 5 % to 10 % has an opposite effect. Formulations containing only 5 % starch with a fairly high concentrations of additives or 40 % starch with no additives supported none or very little growth after three weeks, which indicates the importance of the concentration of starch and the presence of additives on the biodegradability of starch-LOPE film blends. Tensile test results showed that increase in starch content in the range of 20-30 % leads to a decrease in the values of the tensile strength and increase in the values of the elongation-at-break whereas further increase up to 40 % has the opposite effect. Tests with blends containing 40 % starch and no additive or 5 % starch with a fairly high concentration of additives resulted in low yield stresses and high elongation-at-break values. Increase the concentration of oleic acid from 5 % to 10 % in the blends resulted in a decrease in both the yield stress and elongation-ai-break values.