Bifunctional Reinforcement of Green Biopolymer Packaging Nanocomposites with Natural Cellulose Nanocrystal–Rosin Hybrids

Rosin and cellulose nanocrystals (CNCs) are easily extracted from agricultural pines/conifers and natural cellulose, and poly­(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is extracted from agricultural corn stalks, etc. In this study, PHBV and CNC-grafted rosin (CNC-R) hybrids were successfully fabricated by an efficient solution casting. The nanocomposites with a homogenous microstructure were transparent and had strong barrier resistances to water vapor and two food simulants. The synchronous enchantments in mechanical strength/toughness and thermal stability of nanocomposite films were achieved by addition of CNC-R. The T₀ increased by 31.2 °C for the film with 10 wt % CNC-R; meanwhile, the tensile strength and elongation to break were improved by 107.9 and 43.9% for the sample using 5 wt % CNC-R, respectively. Also, compared to neat PHBV, the nanocomposites with 5 wt % CNC-R exhibited excellent barrier properties, antibacterial activity (100.0% antibacterial ratio), and lower migration levels for both food simulants. The appearance of coated grapes with 10 wt % CNC-R nanocomposites at the 11th day was the best compared to those of PHBV and its nanocomposites with a low CNC-R content (1–3 wt %). Thus, our nanocomposites with CNC-R showed a significant application in packaged grape by extended shelf life and had potential applications in bioactive food packaging materials.