Function of chitosan in aDOPO‐based flame retardant modified epoxy resin

Abstract

A bio‐based flame retardant (PDE) was synthesized through a facile one‐pot reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with protocatechualdehyde and ethanol. PDE was fully characterized by fourier transform infrared spectroscopy (FTIR), 1H NMR, 31P NMR and ESI‐MS. Epoxy resin (EP) with 9 wt% PDE (EP/9%PDE) passed UL94 V‐0 rating and possessed the limited oxygen index (LOI) value of 33.2%, the curved EP thermosets kept transparent. When chitosan (CS) was used to replace one‐third of PDE in EP/9% PDE, the modified EP also passed UL94 V‐0 rating with the LOI value of 32.3%, the curved thermosets kept transparent and owned better absorption effect toward ultraviolet light. Cone calorimeter test and TG‐FTIR analysis were performed on the EP samples, the chars after burning were characterized by scanning electron microscope (SEM), energy‐dispersive X‐Ray spectroscopy (EDX), Raman spectrum and FTIR. The results showed that the synergistic effect of PDE‐CS on flame retardant was ascribed to the protective effect of denser char layer, the release of some phosphorus containing free radicals and the dilution effect of released nonflammable gases such as H2O and CO2.

A new‐type terephthalonitrile derivative flame retardant of bi‐DOPO compound with hydroxyl and amino groups on epoxy resin

“…A new-type flame retardant DEZ of bi-DOPO compound containing bi-hydroxy and two amino groups, was synthesized. 1 H NMR, 31 P NMR spectra, and FTIR have determined the chemical structure of DEZ. The LOI of EP composites with 5 wt% of DEZ was 29.7% and EP composites reached a V-0 rating in the UL-94 test, as well as THR was decreased by 11.2% compared with neat EP.…”

“…Thermofisher Nicolet IS5 spectrophotometer has performed Fourier transform infrared spectra (FTIR) analysis. 1 H and 31 Pnuclear magnetic resonance (NMR) spectras were measured on a Bruker AV400 NMR spectrometer (Bruker, Switzerland) with DMSO-d 6 as the solvent. Thermofisher Quanta 400 FEG measurement was applied to the scanning electron microscope (SEM) image.…”

“…Epoxy resin (EP) has excellent mechanical and chemical properties and has been widespread used in coatings, adhesives, architectural decoration, and other fields. 1,2 However, the main constituent elements of EP are C and H, which lead to the flammability of EP and the release of a large amount of heat during combustion. They significantly limit the further application of EP and make it easy to break out of the fire.…”

Flame‐retardant epoxy resin with good smoke‐suppression endowed by chitosan–cobalt/phosphorus complex

“…Although the addition of pure chitosan to EP improved its charring ability, it was not effective in reducing the amount of smoke released during combustion and even increased the heat release. 13 Thus, researchers have prepared a variety of CS derivatives to endow polymer materials with better smoke suppression properties. 14,15 Although chitosan derivatives can reduce the release of smoke, but when used alone, they fails to give EP good flame self-extinguishing behavior (UL-94 V-1 or V-0 rating), need to be used in combination with other flame retardants, such as ammonium polyphosphate and DOPO.…”

“…CS has the potential to be a carbon‐forming agent due to its rich carbon source. Although the addition of pure chitosan to EP improved its charring ability, it was not effective in reducing the amount of smoke released during combustion and even increased the heat release 13 . Thus, researchers have prepared a variety of CS derivatives to endow polymer materials with better smoke suppression properties 14,15 .…”