Construction of CMS@MoS2 core-shell structure to enhance flame retardancy and smoke suppression performance of waterborne epoxy fireproof coatings for steel structures

As a carbon-based flame retardant, carbon microspheres (CMS) not only block heat transfers at low temperature, but also the inert gas produced by its high-temperature decomposition can act as a dilution of combustible gases. However, its barrier effect is limited at high temperature. Herein, CMS were synthesized by a facial hydrothermal method with glucose as raw material. Then, a layer of molybdenum disulfide (MoS2) nanosheets was uniformly loaded on its surface to obtain a novel CMS@MoS2 hybrids with core-shell structure, which was used to improve the fire resistance of composite coating. The results showed that the backside temperature of the composite coating with 3% of CMS@MoS2 hybrids reached the lowest value (173.1 degrees C), revealing its highest heat shielding effect. Moreover, due to the improvement of the synergistic barrier effect of CMS and MoS2 nanosheets on gas and heat at high temperature, the EP/CMS@MoS2-3.0% coating exhibited the maximum expansion height (16.87 mm) and expansion rate (13.18). Meanwhile, the values of Tmax (372.9 degrees C) and carbon residue (30.6%) also reached the maximum, which is due to the catalytic carbon formation effect of Mo atom and the improvement of thermal and mass barrier performance of char layer. Moreover, smoke density tests showed that the EP/CMS@MoS2-3.0% had the lowest SDR (36.4%). Further, the EP/CMS@MoS2-3.0% exhibited the lowest PHRR (577 +/- 13 kW/m(2)), THR (18.71 +/- 0.9 MJ/m(2)), PSPR (0.118 +/- 0.02 m(2)/m(2)) and TSP (2.80 +/- 0.07 m(2)/m(2)) values, demonstrating its excellent flame retardant and smoke suppression properties.