Rigid molecular chains trapped reactive elastomers for high performance PLLA composites with excellent tough-strength balance

The enhancement in the stiffness-toughness balance of PLLA composites poses great challenges. Herein, we proposed a two-step reactive processing strategy to design unique "sub-inclusion" microstructure for high performance polylactide (PLLA) composites. The rigid PLLA chains trapped reactive elastomer (RCRE) was first prepared by the reactive blending of a multiple-carboxyl PLLA (mcPLLA) with the random copolymer of ethylene-acrylic ester-glycidyl methacrylate (EGMA). The pre-grafted mcPLLA chains can be fixed and trapped in the rubber domains, inducing sub-inclusion morphology after the following mixing of RCRE with the virgin PLLA. Promisingly, excellent stiffness-toughness balance can be realized: on the one hand, the notched impact strength of the obtained PLLA alloys was as high as 58.7 kJ/m2, which was more than 8 times of the virgin EGMA toughened PLLA blend (7.0 kJ/m2) at the same EGMA content (15 wt%); on the other hand, the Young's modulus and tensile strength kept almost the same (1.4 GPa and 47 MPa). The synergistic improvement of the PLLA composites is attributed to the sub-inclusion structure in the dispersed rubber domains, as well as the strong interfacial adhesions. This work expands the scope promising to prepare high-performance polymer composites with excellent stiffness-toughness balance via construction of sub-inclusion morphology, and also provides depth of understanding on toughening mechanism for plastic/elastomer system.