Effect of poly lactic acid trays on the optical and thermal properties of recycled poly (ethylene terephthalate)

Abstract

To progress towards a more sustainable plastic system, multiple interventions are required, including the decoupling from fossil feedstock. Biobased plastics therefore have to be integrated in plastic waste management systems. This should, however, not hamper the performance of current recycling systems. Several studies have previously suggested that the uptake of poly lactic acid (PLA) in this system would endanger poly (ethylene terephthalate) (PET) recycling. This study reports the estimated concentration of PLA in recycled PET and the effect of the presence of this impurity on the optical and thermal properties of recycled PET. The current concentrations of PLA in recycled PET in the Netherlands were modelled to vary between 0% and 0.019%. When the PLA consumption rises, the concentration in recycled PET can be kept below 1% with NIR technologies. The impact of 0.1 to 1% PLA in recycled PET on the optical and thermal properties was negligible. Conversely, the negative impact of 0.1% PVC was substantial. Also the impact of 0.1% EVOH on recycled PET was studied and like PLA found to be limited. This study therefore contravenes previous studies on the impact of PLA on the quality of recycled PET. The difference between this study and the previous studies is that within this study, recycled PET has been processed in agreement with industrial methods. Therefore, in case the sorting and recycling facilities maintain their current careful operation, no negative impact of PLA on PET recycling can be foreseen, and further integration of biobased plastics in the plastic waste management system can be pursued.