Rigid epoxy microspheres reinforced and toughened polylactic acid through enhancement of interfacial reactivity

Polylactic acid (PLA), as a biodegradable thermoplastic resin, has received extensive research and attention. However, PLA exhibits severe brittleness at room temperature, which will greatly limit its practical engineering application. Herein, five kinds of epoxy microspheres (EPs, 0.07–20 μm) with high surface reactivity were synthesized by the double emulsion method for toughening and reinforcing PLA. It is found that EPs efficiently improve the toughness of films while maintaining the high tensile strength and modulus. At only 0.5 wt% EPs, the elongation at break of PLA is increased to 19.5%, which is 4.9 times that of pure PLA. The efficient improvement in toughness is attributed to the reaction between surface epoxy groups of EPs and O–H of PLA. Toughening mechanisms mainly involve stress concentration, debonding cavitation, crazing growth and shear yielding plastic deformation. Meanwhile, due to the high rigidity of EPs, the tensile strength and modulus of PLA/0.5% 300 nm EPs film are 15.1% and 7.3% higher than that of pure PLA, respectively. This work exhibits a potential and promising application in toughening and reinforcing PLA.