Synergistic toughening effect of hybrid clay particles on poly(lactic acid)/natural rubber blend

In this study, poly(lactic acid) (PLA) is toughened by blending with natural rubber (NR). In order to induce additional toughening, the hybrid of two clays (natural clay (CNa+) and organically-modified clay (C20A)) showing different localization in the blend is added to the PLA/NR 70/30 blend. For the blend with CNa+ localized in the PLA matrix, linear viscoelastic response (G ', G '') of the blend does slightly change with the decreased drop size or the coarsening of NR as CNa+ content increases. On the other hand, the addition of C20A brings notable rheological response with a significant change in morphology from co-continuous structure (< 0.5 wt%) to compatibilized morphology (> 0.5 wt%). With a small amount of clay (0.75 wt%) where G ' and G '' crossover, the mixture of two clays (CNa+/C20A 0.3/0.45 wt%) inducing different morphologies to the blend causes a synergistic effect to form cocontinuous structure, leading to a synergistic elongation at break over 100%. This study shows that the addition of a small amount of clays less than 1 wt% can induce toughening of PLA/NR by morphology control of well-designed particle localization. Also, linear viscoelasticity analysis is useful to detect a subtle change in blend morphology.