Online observations and process analysis of chain extended polylactides during injection moulding

The present work focuses on the processability and degradation control during injection moulding of two different polylactide grades after chain extension achieved using epoxidized and maleated chain extenders. In the first part of the contribution, the influence of chain extension and the resultant change in the viscosity on the processing parameters, such as injection pressure, melt temperature, or flowability, will be discussed. For this purpose, besides a normalized MFI test, a special investigation methodology, which included a flow-spiral test and the measurement of injection pressure, was employed for online observations. In regards of the flow behaviour, it was confirmed that the different functional groups of the used chain extenders play a dominant role in counteracting the degradation of polylactide. The second part deals with the mechanical performance of modified PLA. It was shown that the chain extension reaction leads to chain branching, and, thus, the crack stopping mechanism is influenced positively. As a consequence, the polymer toughness was affected and the mechanical behaviour improved.