Thermo-rheological probe of microstructural evolution and degradation pathway in the flame-retarded PP/EVA/NOR/clay nanocomposites

We perform comprehensive rheological and morphological investigations of multicomponent system of polypropylene (PP)/ethylene vinyl acetate copolymer (EVA)/Clay/N-alkoxy hindered amine type flame-retardant (NOR) in the presence of two types of compatibilizers. Effects of each component on the relaxation mechanisms were discussed in detail and correlated with the microstructural evolution governed by physical and chemical interactions between the components. Temperature sweep experiments indicated that in the blend nanocomposites, viscosity always increases by increasing temperature. This was found to be related to the migration of nanoclay in the system, originated from new thermodynamic state at the elevated temperatures. Differences in kinetics of morphological evolutions in the blend nanocomposites were explained based on the initial location of clay platelets, Stokes–Einstein relation in association with the rheological properties of the counterpart flame-retarded blend systems, and presence of chemical reactions. Moreover, enhanced miscibility/compatibility between PP and EVA phases at high temperatures was inferred from time sweep rheological data and then visualized using scanning electron microscope. Graphical abstract