Influences of surfactant content and type on physical properties of natural rubber/organoclay nanocomposites

Montmorillonite clay (MMT) was modified by octadecylamine (ODA) or octadecyltrimethyl ammonium bromide (ODTMA) surfactants. The surfactant contents were varied, i.e. 0.5, 1.0 and 2.0 times the cation exchange capacity (CEC) of the MMT. The intercalation of surfactant molecules into MMT layers was confirmed by the increase in interlayer spacing of the modified MMT, the appearance of C-H stretching bands of alkyl ammonium surfactants and the increase in decomposition temperatures of the intercalated surfactant. With increasing surfactant content, the excess amounts of surfactant which had low interaction with MMT surface increased. The MMT-ODA and MMT-ODTMA were used as reinforcing fillers for natural rubber (NR). Effects of surfactant content and type on cure characteristics, tensile and morphological properties of NR nanocomposites were determined. NR nanocomposites containing 5 phr of the organoclays were prepared by a two-roll mill. With increasing surfactant content, morphologies of the NR nanocomposites revealed the exfoliated structure and the good dispersion of the organoclay in the NR matrix. These caused the enhancement of tensile properties of the NR nanocomposites. Among all the nanocomposites, NR/MMT-ODA2 had the highest tensile strength and provided optimum scorch time and cure time.