Mechanical Properties and Anaerobic Biodegradation of Thermoplastic Starch/Polycaprolactone Blends

Abstract

Thermoplastic starch (TPS) has emerged as a readily biodegradable and inexpensive biomaterial that can replace traditional plastics in applications such as food service and packaging. TPS is an abundant, renewable resource with a low processing temperature when compared with other biodegradable polymers. However, TPS has very low strength and it is brittle. Therefore, there is a need to modify it or blend it with other biodegradable polymers to achieve the desired performance. Polycaprolactone (PCL) is a rubbery biodegradable plastic that can be used to improve the ductile behavior of TPS. The goal of this research was to determine the viability of TPS as an inexpensive majority component in polymer blends with PCL. A ductile bioplastic that is cost-competitive can promote the use of compostable packaging. This study also evaluated biodegradation through anaerobic digestion under mesophilic (37±2°C) and thermophilic (52±2°C) conditions. Preliminary studies on the anaerobic degradation of PCL revealed that thermophilic degradation conditions were favorable compared to mesophilic conditions. While mesophilic digestion can work when a high percentage of TPS is blended with PCL, thermophilic conditions offer an advantage even at a lower TPS percentage. Addition of TPS improved the biodegradability of PCL significantly, possibly due to increased surface area of PCL exposed after TPS degrades from the blend.