Comparative Study of M(Ⅱ)Al (M=Co, Ni) Layered Double Hydroxides for Silicone Foam: Characterization, Flame Retardancy, and Smoke Suppression

Abstract

To compare the different actions of the two representative transition metal cations of Co2+ and Ni2+ in layered double hydroxides (LDHs), CoAl-LDH and NiAl-LDH intercalated with CO32− were synthesized, and the chemical structures, microstructures, and surface areas thereof were successfully characterized. Then, the two LDHs were utilized as flame retardants and smoke suppressants for silicone foam (SiF). The densities, flame retardancy, smoke suppression, thermal stabilities, and compressive strengths of the two SiF/LDHs nanocomposites were investigated. The introduction of LDHs slightly decreased the density of SiF due to the catalytic actions of Co and Ni during the foaming process of SiF. With respect to the flame retardancy, the addition of only 1 phr of either CoAl-LDH or NiAl-LDH could effectively improve the limiting oxygen index of SiF from 28.7 to 29.6%. Based on the results of vertical flame testing and a cone calorimeter test, the flame retardancy and fire safety of the SiF were effectively enhanced by the incorporation of LDHs. In addition, owing to the good catalytic action and large specific surface area (NiAl-LDH: 174.57 m2 g−1; CoAl-LDH: 51.47 m2 g−1), NiAl-LDH revealed higher efficiencies of flame retardancy and smoke suppression than those of CoAl-LDH. According to the results of energy-dispersive X-ray spectroscopy, Co and Ni participated in the formation of protective char layers, which inhibited the release of SiO2 into the gas phase. Finally, the influences on the thermal decomposition and compressive strength for SiF resulting from the addition of LDHs are discussed.

Flame-Retardant Cycloaliphatic Epoxy Systems with High Dielectric Performance for Electronic Packaging Materials

“…It is noted that BCEP 1 -TGIC 3 achieves a lower PHRR and THR than the reference sample; in addition, it shows a relatively low FIGRA value of 7.5 kW•m −2 s −1 (FIGRA of ERL-4221 is 12.3 kW•m −2 s −1 ). This indicates that the flame-retardant epoxy system presents a relatively low heat release rate and fire spread rate under simulated fire conditions [34,35]. In addition, due to the incomplete combustion of the flame-retardant material, the cured BCEP 1 -TGIC 3 show a higher TSP than the cured ERL-4221 (39.1 m 2 versus 30.5 m 2 ) and it finally achieves more char residues than the contrast sample (0 versus 4.8%).…”

Flame retardancy, combustion, and ceramization behavior of ceramifiable flame‐retardant room temperature vulcanized silicone rubber foam

“…Generally, introducing flame retardants is the most effective way to improve the flame‐retardant properties of SRF. Many flame retardants have demonstrated excellent flame‐retardant performance in SRF, including aluminum hydroxide (ATH), 10 calcium carbonate, 11 expandable graphite, 12 graphene oxide, 13 dimethyl methylphosphonate, 14 melamine, 15 and layered double hydroxide 16,17 . Nonetheless, these flame retardants have little effect on the integrity and strength of the char layer, implying that they cannot effectively improve the fire resistance of SRF.…”

“…Many flame retardants have demonstrated excellent flame-retardant performance in SRF, including aluminum hydroxide (ATH), 10 calcium carbonate, 11 expandable graphite, 12 graphene oxide, 13 dimethyl methylphosphonate, 14 melamine, 15 and layered double hydroxide. 16,17 Nonetheless, these flame retardants have little effect on the integrity and strength of the char layer, implying that they cannot effectively improve the fire resistance of SRF. The fabrication of ceramifiable polymer composites can achieve the improvement of fire resistance for polymers.…”

Recent advances in metal-family flame retardants: a review

“…It can also promote char formation by suppressing ames in the gas phase through thermal decomposition to produce non-combustible gas dilution. 27,28 This increases ameresistance of the polymer, and they can also reduce emission of smoke and hazardous gases during polymer burning. [29][30][31] The earliest metal-based ame retardants developed were metal hydroxides, most commonly aluminum trihydroxide (ATH) 32,33 and magnesium hydroxide (MH).…”