Surface-Confined Nanoclays in Ethylene Butyl Acrylate Copolymer: Toward Smarter Flame Retardancy

This study explores the development of nanostructured flame-retardant systems using ethylene-butyl acrylate (EBA) copolymer and nanoclays. This was achieved following two strategies: namely, the incorporation of the nanofiller into the bulk material or its confinement to the surface through the utilization of coatings. First, the effectiveness of the bulk approach was evaluated. To this aim, 4 wt.% nanoclays were embedded within EBA, resulting in a 50% reduction in peak heat release rate and a significant delay in flame-out time when compared to the unfilled copolymer. Then, films containing 4 wt.% nanoclay with a thickness of 300 µm produced via compression molding or cast extrusion, were applied as surface coatings to unfilled EBA substrates, yielding an overall clay content of 0.36 wt.% of the total sample. Despite the reduced nanoclay content, the surface confinement proved to be more effective than the bulk incorporation in delaying ignition time (an increase of 20% and 50% compared to the bulk nanocomposite and neat copolymer, respectively), suggesting more efficient initial protective action. Overall, the obtained results indicate that the nanoclay surface localization leads to slower fire propagation and improved fire safety while preserving polymer bulk properties.