Poly(l-lactide) (PLLA) was melt blended with a set of polyethylenes (PE) in an effort to increase the impact strength of the PLLA. As compatibilizers, we prepared a series of molecularly distinct polylactide-polyethylene block copolymers. The influence of the copolymer structure on the matrix/dispersed phase interfacial adhesion was correlated with the mechanical properties of the PLLA composites. For the lowest modulus PE dispersed phase, the block copolymer that gave the strongest interfacial adhesion was necessary to achieve the most significant improvement in toughening. Whereas with the stiffest PE, the block copolymer that gave the weakest interfacial adhesion resulted in the greatest improvement in impact strength. For the intermediate stiffness PE, an intermediate degree of adhesion was necessary to obtain the largest increase in the impact properties. The impact properties of the composites were also found to be highly dependent on the dispersed phase properties.
Bibliographical noteFunding Information:
The authors would like to thank Laura Crawford for performing the tensile testing of the Engage 8540 and Engage 8100 polyethylenes. The authors also thank Professor Christopher W. Macosko and Dr Yonathan Thio for helpful input during the preparation of this manuscript. The David and Lucile Packard Foundation and the Toyota Motor Company are acknowledged for financial support of this work.
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- Interfacial adhesion