Influence of the Degree of Exfoliation of an Organoclay on the Flame-Retardant Properties of Crosslinked Ethylene-co-Propylene-co-diene Monomer-g-Maleic Anhydride-Based Composites

Layered montmorillonite was synthesized by hydrothermal method, progressively modified by an alkylammoniumand thoroughly characterized by elemental, thermal, and X-ray diffraction (XRD) analysis. Pristine and modified clayswere introduced inmaleic anhydride-modified ethylene- co-propylene-co-diene monomer matrix. XRD and transmission electron microscopy investigations showed microcomposite as well as intercalated or exfoliated nanocomposites morphologies depending on the organic content of the clay. The inhibitor character of the pristine clay on peroxides as crosslinking agent for rubbers was then demonstrated and overcome by using electron beam irradiation for specimens containing unmodified clay. Dynamic mechanical analyses and swelling measurements showed that it is possible to obtain the same degree of crosslinking of the polymer matrix by electron beam irradiation of the composites based on pristine clay specimens and conventional peroxide curing of modified-clay-based ones. Finally, flame-retardant properties of different clays-based composites showed a direct dependence on the degree of exfoliation. It was observed that the better the exfoliation, the higher is the flame retardancy. (C) 2015 Society of Plastics Engineers