Dendritic-hydroxyzinc stannate loaded carbon nanotubes for enhancing flame retardancy of composite coatings

Abstract

A novel tree-like flame retardant was used to enhance the fire resistance of epoxy coatings. Specifically, polydopamine (PDA) was firstly deposited on the surface of carbon nanotubes (CNTs) to endow the surface with abundant active groups and high water dispersibility. Afterwards, zinc hydroxystannate (ZHS) was loaded on the surface of CNT/PDA (CPA) by co-precipitation method. The advantage is that it can fully combine the reinforcement effect of one-dimensional CNTs on the carbon layer, the gas phase flame retardant and the catalytic carbon-forming effect of ZHS, thereby obtaining an efficient nanocomposite fireproof coating. The results showed that the CI of the composite coating was greater than its ΔH* value, suggesting that the introduction of nanomaterials helps the curing process of the epoxy coating. The back-side temperature of the composite coating with 3.0 % of CPA@ZHS hybrids reached the lowest value (169.3 °C). Meanwhile, the CPA@ZHS3.0 %/EP composite coating exhibited the maximum expansion height (21.1 mm) and expansion rate (16.36) during calcination. The thermal weight loss test displayed that the CPA@ZHS3.0 %/EP retained the highest amount of carbon residue (30.2 %) due to the catalytic carbon formation of ZHS, which laid the foundation for its high adiabatic properties. In addition, the smoke density rating (36.8 %) of the CPA@ZHS3.0 %/EP was lower than that of the other samples, indicating its best smoke suppression ability. It can be seen that the composite coating can obtain excellent flame retardant and smoke suppression effects under the lower additive amount of nano-additives, which opens up a new avenue for novel and efficient flame-retardant coatings.