Application of Differential Scanning Calorimetry to Assess Molecular Weight Degradation of Poly(butylene Adipate-co-terephthalate)-Based Plastics

The use of biodegradable plastics is increasing as customer expectations toward sustainability are addressed. However, their biodegradation processes, mechanisms, and dynamics in real applications are still not well understood. Commonly available analytical techniques such as differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy can help to better understand the biodegradation kinetics of biodegradable plastics in different environments, e.g., home compost, industrial compost, and soil. Polymer fragmentation, mainly through hydrolysis, is the first stage of biodegradation. Evaluating the evolution of the molecular weight is a challenging measurement in uncontrolled environments, e.g., open soil or ocean, and requires expensive instrumentation and chemical solvents. This work presents how DSC can be used to evidence plastic degradation (e.g., reduction in molecular weight) of biodegradable polybutylene adipate-co-terephthalate-based plastics in home and industrial compost settings. Significant increases in crystallization temperature, T_C, were found in degraded samples using DSC. This increase in T_C was correlated with a loss in reduced viscosity, a metric widely used to infer polymer molecular weight. A positive monotonic relationship was observed, establishing T_C as a possible indicator of polymer degradation.