Regulating tannic acid-crosslinked epoxidized soybean oil oligomers for strengthening and toughening bamboo fibers-reinforced poly(lactic acid) biocomposites

Bamboo fibers-reinforced poly(lactic acid) (BF/PLA) biocomposites were strengthened and toughened with tannic acid-crosslinked epoxidized soybean oil (TA-ESO) oligomer via reactive extrusion. By adjusting the concentration of TA-ESO on the BFs surface, TA-ESO oligomer was designed to localize at the interface of the composites and then to disperse within PLA matrix. As evidenced by FTIR and XPS analyses, a low concentration of TA-ESO oligomer generated strong interactions with BFs via natural polyphenol-inspired chemistry and formed a flexible interfacial layer between the BFs and PLA matrix. The TA-ESO oligomer with a high concentration would diffuse inside PLA matrix as a rubbery phase to toughen the matrix and thus the composites. The strengthening and toughening effects of TA-ESO phase on the BF/PLA composites were fully discussed by investigating the crystallization behavior, tensile properties, impact strength, thermo-mechanical properties, and morphological analysis of the resulting fully biobased BF/TA-ESO/PLA ternary biocomposites.