Influence of modifying agents of organoclay on properties of nanocomposites based on natural rubber

Abstract

Sodium-montmorillonite (Na-MMT) nanoclay was modified with four different modifying agents, differing in alkyl chain lengths. The modified organoclay or modified Na-MMT was then compounded with natural rubber (NR) via melt mixing. The influence of alkyl chain length on the properties of organoclay and NR/organoclay nanocomposites was investigated. The longer alkyl chain lengths were more effective in intercalating and expanding the interlayer spacing of clay. Furthermore, the modification of organoclay accelerated the vulcanization reaction of NR, so that the rubber vulcanizates had an increased degree of crosslinking. The mechanical properties of NR were enhanced by the organoclay filling, and larger organoclays interlayer spacing increased the enhancement. This is due to increasing in the crosslinking density of nanocomposites and better dispersion of organoclay in the rubber matrix. A new technique, temperature scanning stress relaxation (TSSR), was used to characterize thermal-mechanical behavior of the composites. The initial stress correlated well with the mechanical properties of nanocomposites. In addition, stress relaxation was observed at the melting temperature of the agent used to modify the organoclay. The organoclays also enhanced the thermal stability, shifting the stress relaxation peaks to higher temperatures.