The effect of dynamic vulcanization systems on the mechanical properties and phase morphology of PLA/NR reactive blends

Abstract

The effects of dynamic vulcanization systems including sulfur, peroxide, and sulfur/peroxide mixed vulcanization were investigated for dynamically-vulcanized blends of polylactic acid (PLA) and natural rubber (NR) at the PLA/NR ratio of 85/15. For the sulfur system, the CV sub-system (CV1), which used much lower accelerator (TBBS) content than the EV sub-system, rendered higher impact strength and higher %crystallinity. When compared to the peroxide system using DCP as a curative, the impact strength of CV1 sample was almost 4 times lower than the peroxide-cured sample even though their rubber domain sizes and size distributions were comparable. Interestingly, the highest impact strength which was almost 6 times that of the unmodified PLA/NR was achieved when using the mixed sulfur/peroxide system at the CV1/peroxide ratio of 30:70 (S30/DCP70). The lower impact strength of the sulfur-cured system (CV1) compared to those of the peroxide and the mixed-vulcanization systems was potentially due to its significantly higher % crystallinity.