Plasticizing effect of depolymerized suberin derivatives from natural cork and potato periderm in poly(lactic acid) (PLA) for improved toughness and processability

In this study, the inherent brittleness of biodegradable poly(lactic acid) (PLA) was mitigated through the utilization of a carbon-neutral biomass—depolymerized suberin derivatives (DSDs)—as a plasticizer. The DSDs were subjected to repolymerization under mild conditions, resulting in weight-average molecular weights of 2744 g/mol and 11546 g/mol. These polymerized DSDs (pDSDs) were subsequently blended with PLA, leading to a notable reduction in the glass transition temperature of the blends, confirmed through differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) characterizations. Remarkably, the tensile toughness exhibited a substantial increase up to 1148% from 0.56 MJ/m³ in the neat PLA to a range of 4.37–6.99 MJ/m³ for blends incorporating more than 3 wt% of pDSDs. Furthermore, the blends demonstrated a marked reduction in shear viscosity compared to neat PLA, corroborated by an increased melt flow index which shifted from 10.0 g/10 min to a range of 29.3–33.3 g/10 min. This alteration promises to be beneficial in enhancing the quality and producibility during the injection molding process. Importantly, the biodegradability of the pDSDs/PLA blends remained comparable to that of the neat PLA, showing a 90% degree of disintegration in 12 weeks from the biodisintegration test. This study can pave the way to valorize other bio-based materials with aliphatic compounds for the plasticizing modification of various polymers. Furthermore, understanding the interactions between different bio-based aliphatic compounds and various polymers could lead to tailor-made solutions for specific applications, ranging from biomedical devices to structural parts, further broadening the scope of biodegradable and sustainable materials in many engineering fields.