UV-protective and high-transparency poly(lactic acid) biocomposites for ecofriendly packaging of perishable fruits

The past decades have witnessed the archetypal shift from petroleum-based to bioplastics including poly(lactic acid) (PLA) for multifunctional packaging. Here we disclose a microwave-assisted functionalization (MAF) approach to functionalize wood fibers (FWFs) at minute level and high yields (approaching 99 %), conferring high affinity to PLA matrix and significant promotion of mechanical properties. By incorporating of 10 wt% FWFs, the tensile strength and toughness of PLA composite films were elevated to 54.5 MPa and 1.6 MJ/m³, increasing nearly 28 % and over 45 % compared to those of the counterpart loaded pristine wood fibers (PWFs), respectively. It is of significance to note the FWF-enabled unique optical properties for PLA, as exemplified by approximately 100 % UV-blocking ratio (UVR) in the whole UV region with the addition of 20 wt% FWFs. By contrast, the UVR values of PWF-filled PLA (5 %-20 %) gradually decreased as the fiber contents increased, mainly ascribed to the UV reflection at the poorly bonded interfaces and relatively inferior functionality of PWFs. This distinction allowed us to fabricate UV-barrier packaging for preservation of fresh fruits, which were perishable under the UV light of sunshine. The impressive mechanical robustness and high UVR, may prompt affordable and ecofriendly PLA/FWF composites appropriate for packaging.