Nanosilica-Reinforced Epoxidized Natural Rubber Nanocomposites: Effect of Epoxidation Level on Morphological and Mechanical Properties

Epoxidized natural rubbers (ENRs) with three different epoxide contents (i.e., 20, 35, and 50 mol% indicated as ENR20, ENR35, and ENR50, respectively) were prepared. They were then reinforced with 3-methyacryloxypropyl trimethoxysilane-modified nanosilica (MPTS-SiO2). Influence of epoxide level in ENR molecules on morphological, mechanical, and dynamic mechanical properties of the ENR nanocomposites was investigated. The scanning electron microscopy results revealed larger agglomerates of SiO2 were found in the ENR composites with higher epoxide content. Furthermore, the strength and moduli of the ENR nanocomposites increased with increasing epoxide content. However, the optimal tensile strength and elongation at break were observed in the nanocomposites with the intermediate level of epoxide contents. The correlation between the strength properties and the interfacial silica-matrix adhesion indicated that the maximum interfacial adhesion of the nanocomposites was observed in the nanocomposite with ENR35. Also, DMA results indicated stronger interaction between ENR35 and MPTS-SiO2 due to higher storage modulus. (C) 2015 Society of Plastics Engineers