Functionalized liquid polyisoprene as a promising toughening agent for poly(lactic acid): Combining stiffness and toughness

Liquid polyisoprene rubbers (LIR) containing anhydride and carboxylic groups along their chains were successfully employed as toughening agent for poly(lactic acid) (PLA) without great influence on the stiffness of the matrix. In fact, the addition of 5% of these functionalized LIR resulted in an improvement of toughness and impact resistance of more than 2000%, whereas the reduction of the yield stress stayed in the range of 12%. No significant variation of the Young modulus was observed for the modified PLA samples. The effect of the LIR on the rheological and thermal properties of PLA was also investigated. The glass transition temperature obtained from dynamic-mechanical analysis of the PLA matrix was not affected by the addition of 10% of the liquid rubber. The scanning electron microscopy analysis revealed a significant decrease in the rubber domains for the blends containing LIR functionalized with anhydride groups. Finally, the modified PLA with anhydride-functionalized LIR was able to produce transparent film with outstanding mechanical performance than neat PLA, making this material a good option for food packaging. Improvement of Toughness of PLA by addition of 10% of functionalized liquid polyisoprene.image