Activated carbon spheres (ACS)@SnO₂@NiO with a 3D nanospherical structure and its synergistic effect with AHP on improving the flame retardancy of epoxy resin

Abstract

A novel activated carbon spheres (ACS)@SnO2@NiO hierarchical hybrid architecture was first synthesized and applied for enhancing the flame retardancy of epoxy (EP) resin via a cooperative effect. Herein, using activated carbon microspheres as the template, SnO2 and NiO nanospheres were successively anchored to it by a sedimentation‐calcination strategy. The well‐designed ACS@SnO2@NiO significantly enhanced the flame retardancy for consistency of EP composites, as demonstrated by thermogravimetric and cone calorimeter experiments. For instance, the incorporation of 2 wt% ACS@SnO2@NiO decreased by 15.5% maximum in the total smoke production, accompanying the higher graphitized char layer. In addition, the synergetic mechanism of flame retardancy between ACS@SnO2@NiO and aluminum hypophosphite (AHP) was investigated. The obtained sample satisfied the UL‐94 V‐0 rating with a 5.0 wt% addition of AHP and ACS@SnO2@NiO (the ratio of the mass fraction of AHP to ACS@SnO2@NiO is 4.5:0.5). Notably, the incorporation of AHP and ACS@SnO2@NiO resulted in a significant decrease in the fire hazard properties of EP resin; for instance, 4.5AHP‐0.5ACS@SnO2@NiO/EP resulted in a maximum decrease of 32.4% in the total smoke production as compared with that of pure EP resin. It should be noted that the improved flame‐retardant performance for the EP composites is primarily attributed to the synergistic effect of ACS@SnO2@NiO and AHP in promoting the formation of residual char in the condensed phase.

Flame Retardant Epoxy Composites on the Road of Innovation: An Analysis with Flame Retardancy Index for Future Development

“…Hollow symbols are indicative of fiber-incorporated composites with details earlier given in the bottom of Table 1 as notes a to h . Here: 3TT-3BA-20 [169], GN-3 [28], MWCNT-0.8 [29], OMMT-7 [30], OLDH-1, OLDH-5, OLDH-10 [31], MgAl-LDH-2, ZIF8-2, ZIF8@MgAl-LDH-2, ZIF67-2, ZIF67@MgAl-LDH-2 [170], TAT-20 [52], TNB-1, TNB-5, TNB-10, TNB-15, TNB-20 [171], Cu 2 O-21 [55], MH-3, [56], TN-3.42 [63], EG-20 [66], TMT-8 [67], TMT-7 [68], OMMT-1 [77], TAIC-10 [78], TPT-14 [81], HNT-5, HNT-10, HNT@PDA-5, HNT@PDA-10, HNT@PDA@Fe(OH) 3 -5, HNT@PDA@Fe(OH) 3 -10 [172], MMT-6 [94], OPS-5 [102], OPS-4.1, PPSQ-4.1 [103], OPS-4.1, OAPS-4.6 [104], OPS-4.1 [106], ATH-40, C-40, U-40, BA-40, BO-40, MB-30, GB-30 [173], ODPSS-5 [115], Mg-Al LDH-4 [116], T8POSS-10, TGIC-10 [174], RGO-1 [121], HNT-2, LDH-2, LDH-4, LDH-6 [120], AlO(OH)-30 [124], ACS-2, ACS@SnO 2 -2, ACS@SnO 2 @NiO-2 [125], …”

A Phosphorous-Based Bi-Functional Flame Retardant Based on Phosphaphenanthrene and Aluminum Hypophosphite for an Epoxy Thermoset

“…In contrast, 3%HPDAl/EP had a blowing-out effect at the first ignition time, but for the second ignition time, the flame did not extinguish quickly and the flame lasted for a long time. This was because the increase in flame retardant content locked more phosphorus-containing components in residues, as proven by the following XPS results, and formed a P-rich char layer mixed with aluminum pyrophosphate [ 27 , 28 ]. After the second ignition, it was too tough for the generated pyrolysis products to break through the excessively strong carbon layer, so that the quenching effect of phosphorus-containing free radicals cannot be effectively exerted, resulting in a weakened blowing-out effect.…”

Synergistic effect between phosphorus tailings and aluminum hypophosphite in flame‐retardant thermoplastic polyurethane composites

“…In addition, the THR value also presents a reduction of 68%. That could be illustrated by the generation of phosphoric radicals during combustion process which can capture free radicals to hinder the burning . Meanwhile, the AHP will transform to aluminum hydrogen phosphate and aluminum pyrophosphate during thermal degradation, which could promote the carbonization of materials and formation of char layers, thus inhibiting the release of heat .…”