A facile strategy for enhancing tensile toughness of poly(lactic acid) (PLA) by blending of a cellulose bio-toughener bearing a highly branched polycaprolactone

Abstract

In this research, a series of PLA bio-blends with a highly-branched polycaprolactone (PCL)-grafted cellulose biotoughener (CghbP) (i.e., PLA/CghbP series) were facilely fabricated and characterized to improve the tensile toughness of neat PLA. The prepared PLA/CghbP bio-blends were examined by attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy and differential scanning calorimetry (DSC) analysis to be physically intact and partially miscible at the scale of ca.10-30 nm. It was confirmed by the DSC and wide-angle X-ray diffraction (WXRD) analyses that the incorporation of CghbP into PLA matrix can induce a more disordered alpha ' crystalline phase of PLA in the prepared PLA/CghbP blends. The tensile properties of PLA/CghbP bio-blends investigated by universal testing machine (UTM) suggested that the mechanical behavior of highly-tough hard/ soft multiphase polymeric system was realized with the incorporation of 5 wt% CghbP to PLA (i.e., PLA/ CghbP5), resulting in a -215% increase in the tensile toughness (56.1 MJ m-3) compared to pristine PLA (17.8 MJ m-3). This research empirically identified that the improved tensile toughness of PLA/CghbP bearing 5 wt% CghbP are conjunctly correlated with the concurrent formation of more ordered hard PLA alpha crystalline and highly-branched soft phase induced by the loading of an appropriate CghbP into PLA. Furthermore, the PLA/ CghbP5 bio-blend showed remarkably higher migration stability with the weight loss -0.1% CghbP after additive spillage test than those of other PLA/CghbP blends and PLA blends with conventional low molar mass plasticizers.