Fully biodegradable food packaging materials based on functionalized cellulose nanocrystals/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanocomposites

Abstract

Current packaging materials (mainly composed of petroleum-based synthetic polymers) face environmental and disposal issues, and as a result, developing eco-friendly and bio-based nanocomposites as alternatives have motivated academic and industrial research. We report here on our effort to develop a transparent nanocomposite-based packaging film comprised of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and functionalized cellulose nanocrystals (cellulose nanocrystal methyl ester, CNC-me). The resultant CNC-me with hydrophobic ester groups are uniformly dispersed in PHBV without the aid of a compatibilizer or surfactant. Therefore, both the crystallization temperature and crystallinity of the PHBV matrix were increased due to the heterogeneous nucleating effect of CNC-me. With an increase of CNC-me concentration, significant improvements in mechanical performance, thermal stability, barrier and migration properties were achieved, which were ascribed to the improved interfacial interaction and increased crystallinity. Compared to neat PHBV, the tensile strength and maximum decomposition temperature (Tmax) of the nanocomposites all achieved their maximum values at loading levels of 20 wt% CNC-me. Meanwhile the overall migration levels in both non-polar and polar simulants were well below the limits required by the current legislative standards for food packaging materials.