Toughening mechanism of thermoplastic starch nano-biocomposite with the hybrid of nanocellulose/nanobentonite

High flexibility and toughness are key criteria for an effective bioplastic packaging film. However, in most studies, the flexibility of thermoplastic starch (TPS) films is always neglected when targeting their tensile strength improvement. Low film flexibility has limited the development of TPS films in replacing the petrochemical-based plastic packaging films. In this communication, we report a method to produce thermoplastic corn starch (TPCS) films with excellent mechanical strength, high flexibility and high toughness through the hybridization of two natural nanofillers: nanobentonite and nanocellulose. The synergistic effect of the hybrid nanofillers can be observed through the arrangement of alternating nacre structures where the nanobentonite silicate layers are responsible for mechanical strength, while the nanocellulose promotes free volume in the TPCS matrix and triggers high film elongation at break. Structural, morphological, and thermomechanical analysis were conducted, and the detailed strengthening mechanism of the TPCS hybrid nano-biocomposite films was revealed. [Display omitted] •High tensile strength and flexibility TPCS nano-biocomposite films made with hybrid nanofillers.•Natural nanocellulose and nanobentonite form compact nacre structure in the TPCS matrix.•Synergistic effect of the hybrid nanofillers trigger an excellent TPS toughening mechanism.•Nanobentonite induces stiffening effect, nanocellulose responsible for higher chain mobility.•Optimal ratio of nanobentonite/nanocellulose brings the greatest toughening effect.