Abstract
The intermolecular interaction between polylactide (PLA) and the impact modifier can generate high impact energy dissipation upon fracture. In this study graft copolymer impact modifiers that were composed of poly(n-butyl acrylate) (PBA) on the main chain and crystalline poly(L-lactide) (PLLA) on the side chain were prepared to investigate the intermolecular crystallization between the PLLA moiety and the PLA matrix. L-Lactide or D,L-lactide was graft copolymerized with PBA to yield either crystalline poly(n-butyl acrylate-g-L-lactide) (PBGL) or amorphous poly(n-butyl acrylate-g-D,L-lactide) (PBGDL). PBGL/PLA blend and PBGDL/PLA blend were prepared in the melt state, while the PBA content of each blend was fixed at 10 wt%. Annealing of the blends was performed at 100 oC for 4 h to modify the degree of crystallinity. The degree of crystallinity in all blends and neat PLA was increased by about 20% after annealing. The impact strength of the annealed PBGL/PLA blend was twice of that of the unannealed PBGL/PLA blend. However, the impact strengths of the PBGDL/PLA blend was not affected upon annealing, while annealing caused 10% reduction in impact strength of neat PLA and the PBA/PLA blend. The impact strength of the PBGL/PLA blend was found to be improved due to the intermolecular crystallization, resulting in expanded cavitation, debonding, shear yielding and fibrillar structure during fracturing.
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