Mechanical Recycling of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/Polylactide Based Blends

The effects of recycling cycles (up to six repeated cycles) on the structure and properties of neat poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), neat polylactide (PLA) and PHBV/PLA: 50/50 (wt%) blends elaborated by melt molding process were investigated. The changes in the chemical structure, the morphology and the thermal, mechanical and rheological properties of the recycled materials were studied. The reduction of molecular weights of both PHBV and PLA showed the predominance of chain scission mechanism as a result of degradation inducing an enhancement of PHBV chain mobility, as also revealed by the increasing of the PHBV crystallinity measured using differential scanning calorimetry and wide angle X-ray scattering. Nevertheless, all these effects were significantly smaller for neat PLA and PHBV-PLA blends compared to those of neat PHBV. Contrary to PLA, PHBV seems to be relatively more sensitive to the thermomechanical degradation and the presence of PLA in the PHBV-PLA blend tends to partially prevent the degradation of PHBV. Mechanical results evidenced the great recyclability of PHBV/PLA blends, even after six reprocessing cycles, since the values of mechanical characteristics remain more or less constant compared to the initial ones revealing the preservation of the material mechanical properties. A stabilizing effect of PLA on the recyclability of PHBV-PLA blends was highlighted and it can be concluded that the incorporation of PLA in PHBV/PLA blends might be a promising route to extend the PHBV applications.