Synergistic effect of amino silane functional montmorillonite on intumescent flame-retarded SEBS and its mechanism

A functional modified montmorillonite (F-OMMT) was prepared by intercalating pristine montmorillonite using phosphonium salt and subsequent grafting through alkyl amino silane coupling. The synergistic effect of F-OMMT on the flame retardancy and char-forming mechanism of intumescent flame-retarded polystyrene-b-(ethylene-co-butylene)-b-styrene (SEBS) composite (SEBS/IFR) was investigated. When 2 wt % F-OMMT was introduced to the SEBS/IFR composite, the limited oxygen index (LOI) value of the composite increased from 24.9% to 26.9%, and the peak heat release rate significantly reduced according to microscale combustion calorimeter (MCC) test. The outer char demonstrated that F-OMMT produced dense and intact nanoparticles with a stabilised graphite structure. Meanwhile, F-OMMT helped form a crosslinking network containing large amounts of P, O, N, and Si in the char layer. Along with IFR, the amino functional group on the clay released nonflammable ammonia in the gaseous phase, the enhanced blowing effect can overcome the high-viscosity resistance of SEBS, more intumescent coating with strengthened clay platelets was then produced. In addition, the tensile properties of SEBS/IFR/F-OMMT composite increased evidently for the good dispersion effect. F-OMMT can serve as an effective and environmentally friendly additive for SEBS/IFR composite.