Influence of biodegradation on crystallization of poly (butylene adipate-co-terephthalate)

The biodegradation of aromatic-aliphatic biodegradable polyester poly (butylene adipate-co-terephthalate) (PBAT) was studied under mesophilic (37°C) and thermophilic (55°C) anaerobic conditions. Anaerobic sludge from municipal wastewater treatment plant was utilized as an inoculum. Non-isothermal crystallization kinetics of PBAT before and after biodegradation was explored by differential scanning calorimetry. Under mesophilic anaerobic conditions (37°C), the biodegradation after 126 days was only 2.2%, molecular weight changed from 93 000 to 25 500 g/mol, and the crystallization behavior was changed only slightly. However, biodegradation under thermophilic anaerobic conditions (55°C) caused much bigger changes: biodegradation according to biogas production reached after 126 days 8.3%, molecular weight changed from 93 000 to 9430 g/mol, and the crystallization behavior was changed significantly. While T_m increased only slightly, T_c on the other hand increased significantly for the sample after biodegradation at 55°C. Also, the crystallization rate was slower (particularly at lower cooling rates), but crystallinity was slightly higher. The diffraction pattern was observed by X-ray diffraction.