Influence of Glycerol and Clay Contents on Biodegradability of Corn Starch Nanocomposites

In this study, biodegradation of corn starch/glycerol/Na-MMT nanocomposites by soil burial tests were carried out for up to 6 months. Films were prepared by casting method according to central composite design and response surface methodology was applied for analysis of the results. The effects of formulation on the water solubility, contact angle and tensile strength of starch films were investigated. Increasing in Na-MMT content decreased biodegradability; while presence of glycerol, increased it. The effect of nanoparticles content might have been attributed to interactions between starch and Na-MMT that further prevented enzymatic attack on the biopolymer. In addition, the films with higher initial contact angle and lower water solubility revealed slower biodegradation. The effect of glycerol is debated because higher hydrophilicity and weaker mechanical properties enhanced the amylase attack on the samples. Furthermore, weight loss due to soluble matters caused an increase to account of the biodegradability. By increasing in glycerol amount as a water holding agent, the films could store sufficient water content for microbial activities around the buried samples. According to FTIR spectra for partially biodegraded films, the intensity of the peaks associated with starch glycosidic linkages decreased which indicates the action of alpha-amylase produced by soil microorganisms.