Effect of organoclay loading level on mechanical properties, thermomechanical behavior, and heat build-up of natural rubber/organoclay nanocomposites

Sodium-montmorillonite nanoclay was modified with octadecylamine and compounded with natural rubber (NR) by dry mixing method. The effects of organoclay loading level on mechanical properties, thermal–mechanical behavior, and heat build-up of NR/organoclay nanocomposites were investigated. Temperature scanning stress relaxation technique was used to characterize the thermal–mechanical behavior of the composites. The morphological properties were assessed by X-ray diffraction and transmission electron microscopy. Loading levels of organoclay below 5 phr gave improved mechanical properties and heat build-up, along with exfoliated clay structure in the nanocomposites. On the other hand, with loading levels above 7 phr the organoclay tended to agglomerate, and X-ray diffraction revealed an intercalated structure. In these cases, the excess residual organoclay caused significantly increased stress relaxation and heat build-up. Unmodified sodium-montmorillonite as filler did not significantly affect the mechanical and heat build-up properties of NR vulcanizates. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers