Glow-wire evaluation of polymeric materials for the electric sector: Effect of the interlayer spacing of montmorillonite

Abstract In this study the glow-wire technique was used in the evaluation of synergistic effects between organophilic montmorillonites with different basal spacings and an intumescent formulation containing ammonium polyphosphate (APP) and pentaerythritol (PER) in a poly (ethylene- co -butyl acrylate), EBA 30, polymeric matrix. The flammability of the samples was also evaluated through limiting oxygen index (LOI) analyses, UL-94 standard rating and heating microscopy. The morphology of the samples was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). These analyses revealed that processing in a twin screw extruder led to the formation of intercalated and exfoliated nanocomposites. The influence of processing via internal mixer and twin-screw extruder was also evaluated. Glow-wire tests revealed that the addition of montmorillonites with smaller basal spacings led to a synergistic effect with the intumescent formulation, an effect which was not observed when using montmorillonites with basal spacings larger than 30 A. The intumescent materials containing montmorillonites with smaller basal spacings showed GWFI (glow-wire flammability index) as high as 960 °C, which indicates that they could be used in the electrical area.