Controllable layer‐by‐layer assembly based on brucite and alginates with the assistance of spray drying and flame retardancy influenced by gradients of alginates

Abstract

With the aim of tailoring and controlling surface assembly, multifunctional flame retardants (FRs) were obtained based on depositing alginates and silane coupling agents on brucite via the spray-drying-assisted layer-by-layer assembly technique. The assembly was controllable in both structure and gradient mass. Two series of FRs were named CuFR1-3 and NiFR1-3 based on the assembly content of metal alginates. With the assistance of spray drying, good compatibility between FRs and ethylene-vinyl acetate (EVA) was obtained, resulting in better mechanical properties. Meanwhile, the FRs improved flame retardancy and smoke suppression when used in EVA composites. With 55 wt % loading, composites with CuFR3 and NiFR1 passed UL 94 V-0 rating, while those with brucite were not rated. The peak of heat release rate decreased by 51.7 and 49.3% while the residue increased by 9.8 and 11.9%, respectively. The FRs also reduced the smoke and CO production rates. For the two series of FRs, the relationship between FR efficiency and alginate contents is different. The CuFRs assembled more copper alginates and exerted better flame retardancy caused by lower catalytic graphitization. NiFRs exerted a higher catalyzing efficiency at low assembly content. However, at high assembly content, the catalytic graphitization effect would decrease by thermally oxidized degradation leading to excess nickel alginates.

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

“…The nickel alginate‐brucite based flame retardant (NiFR) was prepared by assembling 3‐aminopropyltriethoxysilane, nickel alginate, and vinyl‐(β‐methoxy‐ethoxy) silane in turn with the assistance of spray‐drying technology in our laboratory according to past study. We selected NiFR (named as NiFR1 in Wang et al) as flame retardant due to its best efficiency when used in EVA. The content of Mg (OH) 2 of the selected NiFR was about 83.2 wt% and nickel content was 0.54 wt%; the decomposing temperature at 1 wt% loss was 320°C.…”

“…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 .…”

“…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 . However, this char residue was with low intensity and exhibited fragile hole and cracks, thereby limited its flame‐retardant effect.…”

“…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.…”

“…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. Thereby, we expect the…”