Upgrading of mechanically recycled poly (lactic acid) by use of maleinized linseed oil

In this work, post-consumer PLA bowls were mechanically recycled and further combined with maleinized linseed ( Linum usitatissimum ) oil (MLO) as an environmentally friendly plasticizer. Post-consumer PLA bowls were washed, dried, milled and reprocessed, by melt blending with MLO, into optically transparent thin films (r-PLA), varying the MLO content from 1 to 9 wt% (r-PLA-MLO). The effect of the addition of MLO on the structural, thermal, mechanical, transparency, and wettability properties of PLA matrix was studied. Results of intrinsic viscosity measurement showed that service life and mechanical recycling induced degradation of the polymeric material, evidenced by reduced thermal stability, increased crystallization ability, and modified hydrophobicity. The incorporation of MLO between 1 and 3 wt% led to a notable plasticizing effect, while plasticizer saturation was observed above 5 wt%. Thus, using small amount of MLO, between 1 and 3 wt%, recycled r-PLA-MLO systems showed increased thermal stability, improved flexibility and cold crystallization behavior, without significant reduction of the intrinsic viscosity, due to positive interactions between r-PLA and MLO in the blend. Additionally, all the plasticized PLA-MLO based films were disintegrated under composting conditions at laboratory scale level, proving to be interesting films for agricultural applications. • A novel MLO-based upgrading strategy is presented for recycled post-consumer PLA. • Low MLO loadings (≤3 wt%) improved ductility (+40%) and thermal stability (+8 °C). • High MLO loadings (≥7 wt%) induced phase separation and reduced ductility. • Films disintegrated within 3 weeks under ISO 20200, supporting agricultural use.