Novel C3N4/PANI@PA for enhancement of fire protection and smoke suppression in intumescent fire retardant epoxy coatings

Graphitic carbon nitride/polyaniline doped with phosphoric acid (g-C3N4/[email protected]) hybrids was prepared by polymerising aniline monomer on the surface of g-C3N4 nanosheets, which used an in-situ chemical oxidative polymerisation method. Intumescent fire retardant (IFR) epoxy coatings with g-C3N4/[email protected] were prepared, and fire resistance and waterproofing performance of coatings were investigated. The energy dispersive X-ray spectrometry image showed phosphorus element dispersing evenly on the fracture surface of epoxy composite with 0.25 wt% g-C3N4/[email protected] ([email protected]), which indicated that g-C3N4/[email protected] dispersed in coating evenly. The results of the cone calorimeter test (CCT) showed that the values of peak heat release rate (pHRR), total smoke release (TSR), total carbon monoxide production (TCOP) of pure epoxy resin (EP-0) were 1389.0 kW/m2, 22.6 m2 and 3.6 g, respectively. In addition, the related data of intumescent fire retardant coating (EP-IFR) were 374.8 kW/m2, 12.9 m2, and 2.1 g, respectively. When 0.25 wt% g-C3N4/[email protected] was introduced into EP-IFR to get [email protected] sample, the pHRR, TSR, and TCOP values were reduced to 347.3 kW/m2, 7.9 m2, 1.5 g, which were reduced by 75.0%, 65.0%, and 60.0% compared with EP-0, respectively. Furthermore, g-C3N4/[email protected] could also improve the hydrophobicity of IFR epoxy coatings. The water contact angle increased from 50.0° (EP-IFR) to 84.8° ([email protected]). It was confirmed that g-C3N4/[email protected] could improve the fire protection, smoke suppression performance, and waterproof performance of IFR epoxy coating. All of those provide a certain theoretical support for applying g-C3N4/[email protected] in intumescent fire retardant coatings.