Thermoresponsive Hybrid Colloidal Capsules as an Inorganic Additive for Fire-Resistant Silicone-Based Coatings


Improving the fire-resistant efficiency of silicone-based polymeric coatings is important in the building industry and electrical utilities. In this study, the water-containing hybrid calcium carbonate (CaCO3)-silica (SiO2) colloidal capsule has been developed and optimized as an inorganic flame-retardant additive. This capsule exhibits excellent thermal stability up to 1000 degrees C with a remaining intact hollow spherical structure. When used as an inorganic filler at 15 wt %, it not only reduces the potential fire hazards by over 44% (i.e., the sumHRC reduced from 112.00 J/g K to 62.00 J/g K) but also improves the heat-barrier efficiency by over 30% (i.e., the temperature at the steady state reduced from 350 to 360 degrees C to below 250 degrees C) of the silicone-based polymeric coatings. In addition, the capsule-polymer composite coating exhibits excellent ductility which can withstand heat-induced mechanical stresses and prevent crack propagation under radiative heating conditions. The fire-resistant mechanism of the colloidal capsule is related strongly to the encapsulated water core and the reactions between SiO2 and CaCO3 at elevated temperatures. They not only contribute to a cooling effect on the flammable pyrolysis gases but also induce the insulative effect to the resulted char during combustion. The significant advances in this study will have a high impact in customizing the functional inorganic additives for a better design of the flame-retardant composite coating.



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Pham, ST; Tieu, AK; Sencadas, V; Joseph, P; Arun, M; Cortie, D

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The study is funded by the Australian Research Council (ARC) Discovery Project DP190103455 and Linkage Project LP160101871. The authors acknowledge the use of the JEOL 6490 SEM at the UOW Electron Microscopy Centre.

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