Silicon oxide encapsulated ZIF-8 loaded on reduced graphene oxide to improve flame retardancy of waterborne epoxy coatings

Abstract

Herein, the ZIF nanoparticles were firstly anchored uniformly on the reduced graphene oxide (RGO) surface, and then a layer of silica was deposited on the surface to avoid the negative impact of the pores generated by the decomposition of the ZIF nanoparticles on the thermal insulation properties. The effect of reduced graphene oxide/zeolitic imidazolate framework-8@silicon oxide (RGO/ZIF@SiO2) hybrids on the fire performance of the coatings was analyzed by big plate experiments, furnace test, and thermal weight loss test. The results showed that the backside temperature of RGO/ZIF@SiO2 based intumescent fire-retardant coating (IFR) reached the minimum value (173.9 °C) compared to other samples. The expansion characteristics of the coatings were significantly increased by the addition of nanoadditives. By comparison, RGO/ZIF@SiO2/IFR composite coating exhibited the largest expansion height (21.5 mm) and expansion rate (16.28). Moreover, the IFR loaded RGO/ZIF@SiO2 displayed the highest maximum thermal decomposition temperature (Tmax, 371.1 °C) and residual char (29.8%), indicating its best fire resistance properties. The cone calorimeter test results illustrated that RGO/ZIF@SiO2/IFR had the lowest PHRR (482 ± 21 kW/m2), THR (15.57 ± 0.9 MJ/m2), PSPR (0.10 ± 0.01 m2/m2), TSP (2.01 ± 0.11 m2/m2) and CRR (28.8%) values, indicating its best flame retardant and smoke suppression properties.