Layer-by-layer deposition of copper and phosphorus compounds to develop flame-retardant polyamide 6/montmorillonite hybrid composites

Abstract

Nowadays, increasing attention is devoted to the search for polymeric composite materials that are characterized by reduced flammability. In this work, the layer-by-layer (LbL) technique was applied to form multilayered protective coatings for polyamide 6/montmorillonite (PA6/MMT) hybrid nanocomposites. This time, the double layers LbL deposition was used in order to improve the thermal properties or flammability of PA6 materials. Our goal was to check how five, 10, and 15 triple-layer depositiononto the surface ofPA6 andPA6/MMTcomposites influencedthese relevantproperties. For this reason, disodium H-phosphonate, sodium montmorillonite, and iodo-bis(triphenylphosphino)copper were used for polyelectrolyte solution preparation. Itwas found that the LbLmethod could be successfully used to improve the flammability characteristics of polyamide 6-based composites. Nevertheless, the deposition of the copper complex should be combined with other flame retardants-preferentially containing phosphorus-which enable synergistic effects to occur. Moreover, microscopic observations confirmed that the surfaces onwhich the formation of interwoven fibrous crystal structureswas observed had a tendency to protect the entire material against the destructive effects of heat, contributing, among other things, to reduce the maximum point of heat release rate (PHRR).