Green-plasticized poly(lactic acid)/nanofibrillated cellulose biocomposites with high strength, good toughness and excellent heat resistance

In this paper, nanofibrillated celluloses (NFCs) with network-like structure were extracted from microcrystalline cellulose for the first time through swelling and mechanical shearing. The aim was to study the effect of the novel NFC on the mechanical, thermal, morphological, and crystallization properties of non-plasticized and green-plasticized PLA composites as well as to study the optimal composition of NFC and green plasticizer (ATBC). Interestingly, NFC particle presented a rod-shape as a whole with plenty of nanofibrils on edges. The addition of NFCs not only enhanced the strength and toughness remarkably, but it also improved the thermal stability of PLA composites. The maximum tensile strength, modulus, elongation, and impact strength values (4 wt% NFC content) increased by ca. 37%, 21%, 126%, and 78% compared with pure PLA, respectively. More importantly, after ATBC plasticization, the strength and thermal properties of PLA/NFC composites showed no decrease. Particularly, for 6 wt% NFC content, the strength and modulus of the as-prepared composites were comparable to those of pure PLA, and the elongation and toughness were improved by ca. 259% and ca. 121%. Beyond the above mentioned, wire-drawing and pull-off morphology revealed the evolution process of the molecule and microstructure of PLA during tensile deformation.