Biodegradability of blends based on aliphatic polyester and thermoplastic starch

In this work, biodegradable aliphatic polyester blends of polycaprolactone and polylactide were melted and blended with a natural and biodegradable thermoplastic starch (TPS). The TPS employed in this study was obtained by plasticization of isolated wheat starch using glycerol as plasticizer. Morphology as well as thermal properties of the blends was investigated, and water vapor permeability as a barrier property was also monitored. The biodegradability of the biodegradable blends was performed by a composting process on laboratory scale. The composting process was conducted in an adiabatic closed reactor for 21 days and during the composting process, the temperature, pH value, % moisture and volatile matter and evolved CO2 were monitored. Biodegradation of the blends was determined by weight loss, as well as monitoring of morphological surface change. The thermophilic phase prevailed in the composting process, indicating intensive biodegradation of substrate as well as biodegradation of investigated ternary blends. Since microorganisms use starch as a carbon source, addition of TPS causes considerable acceleration of biodegradation of ternary blends due to higher water vapor permeability as a result of the hydrophilic nature of starch. The thermoplastic starch was first degraded within the blend, which was facilitated access to the microorganisms of other ingredients in the blend, encouraging the biodegradation of other components.