Processing, performance and biodegradability of a thermoplastic aliphatic polyester/starch system

Composites of a biodegradable thermoplastic aliphatic polyester, polybutyle ne succinate adipate (PBSA), with granular corn starch were investigated fo r processability, mechanical and thermal properties, and biodegradability. The PBSA/starch films were prepared with starch contents of 5%-30% by weigh t and processed by blown film extrusion. Increasing the starch content led to an increase in modulus and decreases in tensile strength, elongation to break and toughness. The rate of biodegradation in soil, as measured by res pirometry, increased significantly as the starch content was increased to 2 0% and then plateaued. Scanning electron microscopy revealed that the starc h granules were embedded in the continuous-phase PBSA and that starch promo tes the biodegradation of PBSA. Gel permeation chromatography indicated a m olecular weight decrease for the PBSA after soil exposure and confirmed tha t biodegradation was enhanced by the presence of starch. The results demons trated that the biodegradable PBSA/starch system has mechanical properties useful for blown film applications. (C) 1999 Elsevier Science Ltd. All righ ts reserved.