Recent advances in fire‐retardant carbon‐based polymeric nanocomposites through fighting free radicals

Abstract

Polymeric materials are ubiquitously utilized in modern society and continuously improve quality of life. Unfortunately, most of them suffer from intrinsic flammability, significantly limiting their practical applications. Fundamentally, free-radical reaction is a critical "trigger" for their thermal pyrolysis and following combustion process regardless of the anaerobic thermal pyrolysis in the condensed phase or aerobic combustion of polymers in the gaseous phase. The addition of free radical scavengers represents a promising and effective means to enhance the fire safety of polymeric materials. This review aims to offer a state-ofthe-art overview on the creation of fire-retardant polymeric nanocomposites by adding fire retardants with an ability to trap free radicals. Their specific modes of action (condensed-phase action, gaseous-phase action, and dual-phases action) and performances in some typical polymers are reviewed and discussed in detail.Following this, some key challenges associated with these free-radical capturers are discussed, and design strategies are also proposed. This review provides some insights into the modes of action of free radical capturing agents and paves the avenue for the design of advanced fire-retardant polymeric nanocomposites for expanded real-world applications in industries.

Functionalized Mesoporous Silica Fire Retardant via Hierarchical Assembly for Improved Fire Retardancy of Unsaturated Polyester

“…Specifically, DMMP is released preferentially from the NF3@SiO 2 with increasing temperature, similar to a fire extinguisher. In the gaseous phase, the thermal decomposition of DMMP generates active phosphorus-containing free radicals and captures •H and •OH, thereby interrupting the decomposition of the UP chain . In addition to its main role in the gaseous phase, a DMMP fraction is converted into polyphosphoric acid in the condensed phase, promoting the dehydration and carbonization of the UP to form a protective char layer.…”

Flame-Retardant and Transparent Poly(methyl methacrylate) Composites Based on Phosphorus–Nitrogen Flame Retardants

“…Figure c,d shows several typical absorption peaks of gas-phase decomposition products, and the absorption peaks of −CH 2 and −CH 3 are found at 2981 and 1460 cm –1 , respectively, indicating the escape of hydrocarbons. The absorption peaks of unsaturated olefins (such as olefins and diolefins) can be observed at 3100 and 1640 cm –1 , while the absorption peaks of carbonyl-containing compounds appear at 1740 cm –1 . − During the thermal degradation of PMMA materials containing phosphorus-based flame retardants, some phosphorus-containing units are degraded to small molecules. Therefore, the absorption peaks of P–O–C and P–O–P appear at 1045 and 820 cm –1 , respectively, as shown in Figure d. − On the one hand, the phosphorus-containing unit is pyrolyzed into small molecule monomer volatilized into the gas phase and transformed into the PO • radical trapping agent, which captures H • and • OH radicals generated by the chain radical reaction of PMMA thermal degradation.…”

Preparation and Characterization of Cardanol-Based Flame Retardant for Enhancing the Flame Retardancy of Epoxy Adhesives

“…In addition, the Max-HRR, THR value, and weight loss ratio decreased as the amount of CDPP increased. These results suggest that self-crosslinked CDPP promoted the carbonization of EP series and the formation of the char layer, which inhibited the flame [ 51 , 52 , 53 , 54 ].…”