Abstract: Aiming at improving the char layer strength and fire resistance of intumescent waterborne steel-structure fireproof coatings, titanium dioxide was modified with boron/silicon ceramic precursors and phytic acid, and then incorporated into coatings formulated with an ammonium polyphosphate-pentaerythritol-melamine intumescent flame-retardant system and waterborne epoxy emulsion together with curing agent as film-forming substances, yielding a series of intumescent char-reinforced fireproof coatings. The results showed that, compared with unmodified titanium dioxide, the introduction of modified titanium dioxide enhanced the adhesive strength of the coatings. With increasing proportion of the modified titanium dioxide, the residual char yield and char layer strength after ablation were improved, whereas the expansion ratio decreased. Notably, the backside temperature of the PBSTi/FPC-2 sample was only 266.4 ℃ after continuous methane-jet torch ablation for 20 min. In addition, compared with the fireproof coating without modified titanium dioxide, its peak heat release rate, total heat release, and total smoke production were all reduced, which is attributed to the participation of modified titanium dioxide in forming a dense and continuous intumescent char layer that effectively impedes heat transfer and reduces the release of combustible volatiles and smoke particles.

Key words: intumescent fireproof coatings, modified titanium dioxide, thermal insulation, combustion performance, char layer strength