EFFECT OF MODIFIED KAOLINITE BY USING FATTY ACIDS ON NR- AND SBR-REINFORCED COMPOSITES

Abstract

ABSTRACT Natural rubber (NR) and styrene butadiene rubber (SBR)–kaolinite clay (KC) composites (NR-KC and SBR-KC) were synthesized and characterized. The interfacial surface between rubber and KC was investigated in the presence of stearic acid (SA), palmitic acid (PA), and oleic acid (OA) coupling agents. A monolayer of modifiers was formed on the surface of KC particles. X-ray diffraction (XRD) was carried out to study the effect of fatty acid coupling agents on KC. Modifier concentrations were determined using an adsorption isotherms technique. Sedimentation rate and volumes of modified KC in toluene were measured. Rheometric characteristic and physico-mechanical properties of rubber composites were investigated. Stress–strain behavior and hardness of NR-KC and SBR-KC composites were studied. Experimental results were compared with calculated results using the Cambridge Engineering Selector program. The XRD patterns showed a decrease in the peak intensity of unmodified KC compared with modified KC, asserting an intercalation process. The optimum concentrations of chemical modifiers are 16 × 10−5, 18 × 10−5, and 37 × 10−5 mol/g for SA, OA, and PA, respectively. Mechanical testing showed that high tensile strength can be obtained in the presence of the SA modifier. The degree and kinetics of equilibrium swelling and soluble fraction for NR and SBR vulcanizates were investigated.