Combustion behaviour of EVA/fluorohectorite nanocomposites

Octadecylammonium (ODA) or aminododecanoic acid (ADA) exchanged fluorohectorite (FH) was dispersed in ethylene-vinyl acetate copolymer (EVA) in an internal mixer. A nanocomposite was obtained in the case of FH/ODA with exfoliation of the FH crystalline layers which were separately distributed in EVA as shown by X-ray diffraction (XRD). Whereas distribution of particles formed by multiple crystalline layers with overall size of the order of 1 micron resulted in the case of FH/ADA. In the horizontal combustion mode of the mass loss calorimeter, the nanocomposite shows acceleration of EVA deacetylation and delayed volatilisation of the resulting polyene. The overall heat release rate is much lower than in the case of EVA as measured by the gas combustion temperature. A partial protection of EVA from the flame is also found in the case of the immiscible composite although in this case the volatilisation of the polymer during combustion occurs at a larger rate than in EVA alone. Cumulation of the silicate on the surface of the burning specimen may create a protective barrier to heat and mass transfer which is however much more effective in the case of ablative reassembling of crystalline layers of the nanocomposite than in that of the particles of the immiscible composite. Dripping of burning particles in vertical combustion is suppressed only in the case or the nanocomposite which reduces the hazard of fire spread to surrounding flammable materials. (C) 2001 Elsevier Science Ltd. All rights reserved.