Improving the Biodegradability and Mechanical Strength of Corn Starch-LDPE Blends through Formulatio

Six corn starch-LDPE film blends containing starch in the range 5-40 % by weight,oleic acid as a Lewis catalyst with concentration of either 5 % or 10 %, maleicanhydride as a coupling agent with concentration of either 2 % or 10 % and benzoylperoxide as free radical initiator with concentration of either 0.1 % or 0.25 % wereprepared. Fungal growth tests (ASTM G21) using Penicillium funiculosum were carriedout on the samples made according to the above formulations. Tensile tests (ASTMD638) and SEM imaging were also carried out on the samples before and after incubationwith Penicillium funiculosum for three weeks. The results of ASTM G21 test and SEMimaging showed that the increase in starch content from 5 % to 40 % in the formulationscontaining all three additive increases the biodegradability of the samples whereasincrease 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 or40 % 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-LDPE 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 furthe 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- at-break values.