Polypyrrole combined with phenylzirconium phosphate loaded carbon spheres for reinforcing flame protection of composite coatings

Abstract

Carbon spheres (CS), an emerging carbon-based nano-filler, suffer from high smoke production and limited enhancement when used alone to improve the fire performance of polymers. For this reason, polypyrrole (PPy), a polymer with a high nitrogen content, was first covered on the CS surface in order to obtain a stable C-N network structure during combustion, thus enhancing the strength and isolation of the carbon slag. Afterwards, zirconium phenyl phosphate (ZrPP), an efficient flame retardant, was immobilised on the CS/PPy surface to obtain the CS/PPy@ZrPP composite filler. The incorporation of ZrPP not only improved the physical barrier effect, but also catalyzed the further cross-linking of some cracked small molecules into carbon. Test results demonstrated that the CS/PPy@ZrPP filled EP possessed the lowest backside temperature (169.7 ℃), the largest expansion height (24.1 mm) and the expansion rate (18.83), which determined the most excellent insulation against heat/oxygen. The thermal weight loss analysis indicated that the carbon retention rate of CS/PPy@ZrPP/EP was increased by 42.1% compared to pure EP due to the positive effect of the catalytic carbon formation of ZrPP. Additionally, the smoke density rating of CS/PPy@ZrPP/EP was reduced from 66.1% (EP) to 40.7%, reflecting the effective suppression of the smoke production process. Furthermore, the CS/PPy@ZrPP/EP exhibited a denser and more complete carbon layer, which is in agreement with its most notable ability to insulate against heat.