Dispersion and flame retardancy of ethylene vinylacetate/layered silicate nanocomposites using the masterbatch approach for cable insulating material

Ethylene vinylacetate (EVA) copolymer-based nanocomposites with maleic anhydride-grafted ethylene-vinylacetate (EVAgMA) and organically modified clay (o-clay) were prepared in a twin screw extruder by following a two-step melt compounding method. EVAgMA/o-clay masterbatches with various clay contents up to 50 wt% were examined, after which the masterbatch with the highest clay content was melt compounded with EVA for the preparation of EVA/o-clay nanocomposites containing specific amounts of clay. Further morphological dispersion of the clay particles by highly polar EVA and shearing was confirmed in the EVA/o-clay nanocomposites by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These morphologies led to increased thermal properties in air as well as a considerable decrease in heat release rate (HRR). EVA/o-clay/MDH nanocomposites were also prepared using a high clay-bearing masterbatch to confirm the synergistic flame retardancy of clay as a co-additive in EVA/MDH composites. EVA/o-clay/MDH nanocomposites prepared by substituting o-clay for MDH showed significantly lower and wider HRR during combustion compared to EVA/MDH composite.