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

Abstract

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.

Feasibility of Reprocessing Natural Fiber Filled Poly(lactic acid) Composites: An In-Depth Investigation

“…Both types of molecular weights, weight averaged ( ) and number averaged ( ), showed a decrease with successive recycling. These results agree with the work of other researchers [25]. The polydispersity index (PDI) showed an increase with increased number of reprocessing cycles.…”

Long-term properties and end-of-life of polymers from renewable resources

“…Traditional simulation of mechanical recycling by multiple processing and servicelife by accelerated thermal ageing was previously developed for commodities such as PE [264], PP [265], poly(styrene) (PS) [191], [192], poly(vinyl chloride) (PVC) [266] or PET [179], [267]- [269], among others. Concerning bio-based polymers, the main effort has been dedicated to PLA in great extension, and other materials such as PHAs [270]- [272], poly(caprolactone) [273] or biocomposites with matrixes of PLA or thermoplastic starch (TPS) [274].…”

“…Studies focused on the characterization of multi-injected PCL have revealed that PCL technological waste is suitable to be reused as an additive to a neat polymer [273]. Regarding PHAs, their performance of mechanical recycling was tested during successive injection [270], [271] and extrusion cycles [272], showing successive diminution of molecular weight after increasing cycles, with its consequent decrease in mechanical properties. within the same polymer fraction, or in combination with other material, which hinders the continuation of material flow inside the mechanical recycling loop and thus suggests the design for further valorization.…”

Dynamic mechanical properties of PLA/PHBV, PLA/PCL, PHBV/PCL blends and their nanocomposites with TiO2 as nanofiller

“…Wu et al [31] reported an improvement in the miscibility between PLA and PCL when multiwalled carbon nanotubes were added, which was attributed to the emulsification that occurred at the interface in the presence of the amphiphilic carboxylic MWCNTs, leading to a thermodynamic stabilization of the interface. PLA/PHBV blends and their blend nanocomposites were also studied, but to a lesser extend [2,[38][39][40][41]. Ma et al [2] reported that the storage modulus of PLA was higher than that of PHBV in the glassy state, and blending of the polymers and an increase in the PHBV content reduced the storage modulus of PLA.…”