Disintegration of PBAT/PLA blown films modified with chain extending cross-linkers

A biodegradable blend of PBAT – poly(butylene adipate-co-terephthalate) and PLA – poly(lactic acid) for blown film extrusion was modified with four multi-functional chain extending cross-linkers (CECL). The anisotropic morphology introduced during film blowing affects the degradation processes. As two CECL cause chain scission and the other two cross-linking, their compost (bio-)disintegration behavior was significantly altered with respect to the unmodified reference blend. The disintegration behavior at 30 and 60 °C was investigated by determining mass changes, Young’s moduli, tensile strengths, elongations at break and thermal properties. In order to quantify the disintegration behavior, the hole areas of blown films were evaluated after compost storage at 60 °C to calculate the kinetics of time dependent degrees of disintegration. The kinetic model of disintegration provides two parameters: initiation time and disintegration time. They quantify the effects of the CECL on the disintegration behavior of the PBAT/PLA compound. DSC revealed pronounced annealing effect after storage in compost at 30 °C, and the occurrence of the additional step-like increase of the heat flow at 75 °C after storage at 60 °C. The disintegration consists of processes which affect amorphous and crystalline phase of PBAT in different manner that cannot be understood by a hydrolytic chain degradation only.