Toughening Effect of Clay Particles on Poly(Lactic Acid)/Natural Rubber Blend

In this study, the effect of clay particles on toughening behavior of poly(lactic acid) (PLA)/natural rubber(NR) blend is investigated. PLA and NR were blended in various compositions (70/30, 60/40 and 50/50 PLA/NR) with two types of clay, organoclay and natural clay (Montmorillonite). Linear viscoelasticity analysis and morphology observation of the blends were carried out to investigate change in the blend morphology in the presence of clay. As the NR content increases from 30 wt% to 50 wt%, the NR domains coarsens, changing the blend morphology from droplet to apparent co-continuous structure. With the change in the blend morphology, tensile behavior of the blend including tensile strength and elongation at break differs. Besides, the addition of clay to the blend affects the blend morphology in different way, especially depending on the localization and the clay content. Natural clay localized in the PLA phase induces coalescence of the NR droplets while organoclay reduces the NR drop size due to interfacial localization of clays in the PLA/NR blend. For the droplet morphology, toughening behavior of the PLA/NR blend improves (~ 60% elongation at break of 70/30 PLA/NR blend) only when a small amount of organoclay (0.5 wt%) is added. On the other hand, the 50/50 PLA/NR blend with the apparent co-continuous morphology improves the elongation at break as clay content increases regardless of the type of clay.