Study on the biodegradation of thermoplastic starch and bacterial cellulose based sandwich panel biocomposites

There is currently a growing interest in biopolymers, such as bacterial cellulose and thermoplastic starch, which are renewable and abundantly available in nature. This study investigated the multilayer sandwich composite with thermoplastic starch and bacterial cellulose, using water (TPS/BC-w) and glycerol (TPS/BC-g) as coupling agents. The composites produced by compression molding resulted in a homogeneous, transparent and flexible structure. TPS/BC-w showed superior mechanical property and better adhesion compared to TPS/BC-g. Therefore, the permeability, biodegradation, hydrothermal aging and stability analyses were conducted only for TPS/BC-w. The water vapor permeability of TPS/BC-w is 6.7 times lower than that of thermoplastic starch, indicating better barrier performance. Thermoplastic starch and bacterial cellulose degraded in about 9 days, and TPS/BC-w degraded in 60 days. Biodegradation analysis by CO₂ release confirmed the complete biodegradation process, with CO₂ emissions of 57 %, 42.5 % and 39.6 % after 120 days for thermoplastic starch, bacterial cellulose and TPS/BC-w, respectively. TPS/BC-w remained intact for more than a year, in an environment without direct contact with soil or water. These results indicate that TPS/BC-w composed of natural macromolecules may exhibit functional properties and is useful for applications such as short-shelf-life packaging, particularly for dry products, due to its barrier properties and controlled biodegradability.