Bioplastics Made From Starch as Conventional Plastic Substitutes: Evaluation of Physical Properties and Biodegradation

Abstract This work studies the biodegradability of bioplastics (BPs) generated from the combination of starch from the fruit of Sechium edule (SSE) and the starch of Phaseolus vulgaris (SPV) with a plasticizing agent. BPs were obtained using the casting method from filmogenic solutions formed with dispersions of SSE and SPV in concentrations of 1, 3, 5, 6, 7, and 9% w/v individually and in binary combinations at a (1:1) ratio. Those with the best physical properties were chosen to evaluate the biodegradation of BPs in vitro, over-soil (OS), and soil burial (UG) conditions. The results indicated that BPs are transparent and have a high hydrophilic capacity; they also presented high manageability, continuity, and uniformity aspects starting from a concentration of 6% (w/v). The BPs formulated with the starch mixtures (SSE-SPV) show hardness values between 455.20 and 1972.00 gf and an elasticity index greater than 0.86. Under storage conditions of 11.30 and 57.60% RH, the maximum elongation value was reached from the concentration of 6% SSE-SPV, and this property is reduced when the relative humidity of the BPs increases. Under UG conditions, the percentage of biodegradation was 91.02%, with a degradation rate of 7.6854 mg BP/day, the experimental data of the biodegradation process were adjusted to a first-order kinetic model, the biodegradation rate coefficients of BP were 0.1143, 0.0905, 0.6873 days-1 in in vitro, over-soil and soil burial conditions, respectively.