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., 37:1735–1743, 2016. © 2014 Society of Plastics Engineers