Water resistance, mechanical properties and biodegradability of methylated-cornstarch/poly(vinyl alcohol) blend film

The main shortcomings of biodegradable starch/poly(vinyl alcohol) (PVA) film are hydrophilicity and poor mechanical properties. With an aim to overcome these disadvantages, cornstarch was methylated and blend films were prepared by mixing methylated-cornstarch (MCS) with PVA. The mechanical properties, water resistance and biodegradability of the MCS/PVA film were investigated. It was found that MCS/PVA film had higher water resistance than the native starch/PVA film. However, the water resistance of MCS/PVA films did not have significant difference with the increase in the degree of substitution (DS) of the methylated starch from 0.096 to 0.864. Enzymatic, microbiological and soil burial biodegradation results indicated that the biodegradability of the MCS/PVA film strongly depended on the starch proportion in the film matrix. The degradation rate of starch in the starch/PVA film was hindered by blending starch with PVA. Both tensile strength and percent elongation at break of the MCS/PVA film were improved as DS of the methylated starch increased. Conversely, increasing the methylated starch proportion in film matrix deteriorated both tensile strength and percent elongation at break of the film.