Influence of addition of organic fillers on the properties of mechanically recycled PLA

Abstract

Poly(lactic acid) (PLA) is one of the most used biobased and biodegradable polymers. Due to their high stability, some of the newest grades of PLA are only degradable under severe industrial conditions. For these grades, mechanical recycling is a viable end-of-life option, with great environmental advantages. However, the polymer undergoes degradation during its service life and in the melt reprocessing, which leads to a decrease in properties that can compromise the demand for recycled plastic. The goal of this work was to evaluate the usefulness of adding small amounts of two organic fillers, during the recycling process, for improving the properties of the recycled plastic. The two organic fillers, chitosan and silk fibroin nanoparticles, are obtained from renewable resources. The behavior of the recycled plastics depends on the degradation level of the aged polymer and the nature and amount of the organic filler added. The fillers reduce the further degradation during the melt reprocessing of PLA previously subjected to severe hydrolysis, thus increasing the intrinsic viscosity of the recycled plastic. A careful selection of the organic filler added, based on the nature of the aged plastic, lead to recycled plastics with significant improvements in key mechanical, thermal and barrier properties. Thus, the use of organic fillers obtained from renewable resources can be the basis of a cost-effective and environmentally sound way for improving the mechanical recycling of plastics such as PLA.