Reactive Micro-Crosslinked Elastomer for Supertoughened Polylactide

Elastomer toughening of plastics is extensively acknowledged as a robust route to develop high-performance materials. However, the drastic sacrifice of tensile strength resulting from overloading of the elastomer remains unresolved. So far, the elastomers used as toughening agents are mainly non-crosslinked since linear chains are usually considered to exhibit superiority in adsorbing the impact energy. Herein, we found that the micro-crosslinking of a commercially available linear elastomer, ethylene-acrylic ester-glycidyl methacrylate terpolymer (EGMA), is significantly beneficial for the toughening of polylactide (PLLA). The reactive micro-crosslinked EGMA (RMCE) with various crosslinking densities was feasibly fabricated through melt processing and used as a more efficient toughener for the brittle PLLA than the linear elastomer. The notched impact strength of the PLLA/RMCE was 35.9 kJ/m2, which was more than 5 times that of PLLA/EGMA (7.0 kJ/m2) at the same 15 wt % elastomer loadings. At the same time, the tensile strength and Young's modulus kept high values of 51 MPa and 1.4 GPa, respectively. Synergistic effects such as wide domain size distribution, small ligament thickness, and suitable interfacial adhesion were believed to be main contributors of the increase. The toughening mechanism was further clarified. This work provides a novel avenue to achieve supertoughened PLLA and new insights into the toughening mechanism as well. Such a feasible, versatile, and low-cost method should be widely applicable.