Effects of Glycerin and Carboxymethyl Cellulose on the Mechanical, Water-solubility and Soil-burial Biodegradation Properties of Corn-starch Bioplastic Films

Starch-based films are being investigated as potential alternatives to petroleum-derived plastics, but brittleness and sensitivity to water restrict their performance. This study examined the separate effects of glycerin and carboxymethyl cellulose (CMC) on corn-starch films prepared by solution casting. The glycerin series contained 0, 10, 20, 30 or 40 mL of glycerin per 10 g of starch, while the CMC series contained 0, 1.0, 1.5, 2.0 or 2.5 g of CMC at a constant, but unspecified, glycerin level. Tensile strength, elongation at break, water solubility and soil-burial mass loss were assessed. Across the glycerin series, tensile strength decreased from 32.0 to 6.0 MPa, while elongation at break increased from 10.0% to 65.0%. Water solubility increased from 33.0% to 82.0%, and soil-burial mass loss increased from 27.5% to 88.0%. In the CMC series, tensile strength rose from 12.0 to 90.0 MPa and elongation at break from 15.0% to 75.0%; water solubility declined from 34.9% to 6.38%, while soil-burial mass loss increased from 5.8% to 55.0%. The findings indicate different property trends for the two additive series. However, the series cannot be directly compared because their baseline formulations differ. In addition, soil-burial mass loss does not establish microbial mineralisation. These results provide preliminary information for selecting corn-starch film formulations, subject to further methodological validation.