Preparation of natural rubber-OMMT nanocomposites using mechanical mixing and acid free co-coagulation methods: effect of processing method on mechanical properties

Abstract

The masterbatches were prepared by acid free co-coagulation (AFCC) method in which OMMT was incorporated into natural rubber latex (NRL) or conventional mechanical mixing. Inherent slow coagulation, and drying, stages of the AFCC method were overcome by introducing a novel gelling agent; a combination of two surfactants, namely, Cetyl tri methyl ammonium bromide (CTAB) and Sodium dodecyl sulphate (SDS). Six nanocomposites (A-nanocomposite, C-nanocomposite and M-nanocomposite) were prepared at the OMMT loadings of 2 and 5 phr; of them, two with gelling agent (A-2, A-5) and two without gelling agent (C-2, C-5) using AFCC method and two using mechanical mixing (M-2 & M-5). Controls of them (A-0, C-0 and M-0) were prepared without using OMMT. X-ray diffractograms and scanning electron spectroscopic images showed that a higher amount of aggregated clay structures was present in the M-nanocomposites, and less aggregated clay structures were present in C-nanocomposites. However randomly distributed ordered structures along with exfoliated clay structures were in the A-nanocomposites. Crosslink density and the bound rubber content of the A-nanocomposites were significantly higher than M-nanocomposites but lower than C-nanocomposites. The mechanical properties of the A- nanocomposites and C-nanocomposites were greater than those of the M-nanocomposites at each OMMT loading. The cure time of the A-nanocomposites and C-nanocomposites were also remarkably lowered compared to the M-nanocomposites. It was observed that the effect of the combined gelling agent had no adverse effect on mechanical properties.