Effect of weak intermolecular interactions in micro/nanoscale polyphosphazenes and polyethylene terephthalate composites on flame retardancy

Abstract

This study investigates the effects of weak intermolecular interactions on the flame retardancy of a poly(ethylene terephthalate) (PET) and polyphosphazene flame retardant. Monodispersed poly-(cyclotriphosphazene-co-4,4 0 -sulfonyldiphenol) (PZS) microspheres with different diameters were synthesized by controlling the reactant concentration. Simulation studies revealed that the weak intermolecular interactions between PZS and PET predominantly include strong hydrogen bonding and π-π interactions. The weak intermolecular interactions imparted high thermal stability, even in the molten state, and PZS microspheres with smaller diameters achieved stronger hydrogen bonds and π-π interactions with PET. The diameter of the PZS microspheres influenced the limiting oxygen index value and UL-94 rating. Increasing the carbon residue alone was insufficient to promote the flame retardancy, and the weak intermolecular interactions played an important role. Thus, stronger weak-intermolecular-interactions are beneficial for realizing a material with superior flame retardancy and anti-dropping performance.

Fire retardant polyethylene terephthalate containing 4,4′-(hexafluoroisopropylidene)diphenol-substituted cyclotriphosphazene microspheres

“…For one thing, the chain reactions between the •H radical and •O radical in gas phase might be stopped by the •PO radical produced by the pyrolysis of PZAF. 54,55 For another, PZAF was involved in the charring process. More phosphate esters could be generated by the pyrolysis of PZAF, which encouraged the development of char residues.…”

Synthesis and Characterization of a Novel DOPO-Based Flame Retardant Intermediate and Its Flame Retardancy as a Polystyrene Intrinsic Flame Retardant

“…However, polystyrene is easy to burn when heated, which will release toxic gases and a large amount of smoke, and can melt, drip, and flow in the combustion process, thus making the fire spread. Therefore, it is imperative to improve the flame retardant performance of polystyrene. − According to the flame retardant system, it mainly includes mineral flame retardant, halogen flame retardant, phosphorus flame retardant, silicone flame retardant, biobased flame retardant, and so on. − Among them, halogen flame retardants are all the rage, but they are prohibited because of their toxicity and bioaccumulation. ,,− Phosphorus flame retardants have attracted much attention because of their excellent flame retardant efficiency and environmental friendliness, and have gradually become one of the research hotspots in today’s society. ,,,− Phosphorus flame retardants mainly include ammonium polyphosphate, aluminum hypophosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and its derivatives. ,,,, Phosphorus flame retardants will produce phosphoric acid or similar substances during thermal degradation, which can inhibit the combustion process of the condensed phase. In addition, PO · radicals produced by phosphorus flame retardants have a gas phase flame retardant effect. ,, …”

Effect of aluminum diisobutyl hypophosphate in polyethylene terephthalate and its flame retardant mechanism

“…Therefore, the interaction between the flame retardant and polymer molecules plays a crucial role in enhancing the final flame retardant properties. 10 Besides, the structures of flame retardants largely affect the final flame retardant performances, such as the types of metal and alkyl in alkyl hypophosphate. 6 The metal type mainly affects the condensed phase to enhance the flame retardant performance.…”