Spray-Drying-Assisted Layer-by-Layer Assembly of Alginate, 3-Aminopropyltriethoxysilane, and Magnesium Hydroxide Flame Retardant and Its Catalytic Graphitization in Ethylene–Vinyl Acetate Resin

Abstract

Alginates (nickel alginate, NiA; copper alginate, CuA; zinc alginate, ZnA) and 3-aminopropyltriethoxysilane (APTES) were alternately deposited on a magnesium hydroxide (MH) surface by the spray-drying-assisted layer-by-layer assembly technique, fabricating some efficient and environmentally benign flame retardants (M-FR, including Ni-FR, Cu-FR, and Zn-FR). The morphology, chemical compositions, and structures of M-FR were investigated. With 50 wt % loading, compared with EVA28+MH, the peak heat release rate, smoke production rate, and CO production rate of EVA28+Ni-FR decreased by 50.78%, 61.76%, and 66.67%, respectively. The metals or metal oxide nanoparticles arising from alginates could catalyze the pyrolysis intermediates of EVA into graphene and amorphous carbon, which could bind the inorganic compounds (the decomposition products of MH and APTES) together and form some more protective barriers. For each M-FR, the flame retardant and smoke suppression efficiency were different, which were caused by the diverse carbonization and graphitization behaviors of three alginates. ZnA generated some ZnO aggregations and could not catalyze the graphitization of intermediates. For CuA, the catalytic graphitization was limited by the tightly binding graphene layer. As for NiA, the configuration of the Ni atom could not provide strong binding of Ni substrate and carbon. The liquid-like Ni nanoparticles could restructure and get out from firm graphene shells, so the catalytic graphitization of NiA was efficient and sustainable. This work displayed the catalytic graphitization mechanism of alginates while exploring a simple and novel strategy for fabricating efficient green flame retardants.

Effect of natural basalt fiber for EVA composites with nickel alginate‐brucite based flame retardant on improving fire safety and mechanical properties

“…Among these volatiles, benzene skeleton and ester groups, which were likely to generate crosslinks particles derived from light-extinction precursor, obviously decreased. 12 And in the 475°C peak, 3BF/52NiFR released more CO 2 produced by complete combustion, and less C-H, benzene skeleton, and ester groups, leading to the reduction of smoke production.…”

“…Recently, layer‐by‐layer assembly for fabricating FRs has been considered feasible, which can deposit multifunctional modifier onto FR particles . Among these agents, silane coupling agents for improving compatibility and transition metals for promoting charring effect have been widely concerned .…”

“…Among these agents, silane coupling agents for improving compatibility and transition metals for promoting charring effect have been widely concerned . In our past studies, several metal alginates and silane coupling agents have been layer‐by‐layer deposited onto brucite particles, which enhanced both charring effect and the interfacial interaction with polymers . Among these FRs, the nickel alginate‐brucite based NiFR exerted highest efficiency in promoting charring when used in EVA composites .…”

“…10,11 Recently, layer-by-layer assembly for fabricating FRs has been considered feasible, which can deposit multifunctional modifier onto FR particles. [12][13][14] Among these agents, silane coupling agents for improving compatibility and transition metals for promoting charring effect have been widely concerned. [15][16][17][18][19] In our past studies, several metal alginates and silane coupling agents have been layer-by-layer deposited onto brucite particles, which enhanced both charring effect and the interfacial interaction with polymers.…”

“…[15][16][17][18][19] In our past studies, several metal alginates and silane coupling agents have been layer-by-layer deposited onto brucite particles, which enhanced both charring effect and the interfacial interaction with polymers. 7,12 Among these FRs, the nickel alginate-brucite based NiFR exerted highest efficiency in promoting charring when used in EVA composites. 13 However, this char residue was with low intensity and exhibited fragile hole and cracks, thereby limited its flame-retardant effect.…”