A water-based flame-retardant coating with cenospheres

This work explores how cenospheres (hollow microsphere) can provide a flame-retardant ability to the waterborne acrylic coating. For this purpose, the intumescent fire-retardant coating was prepared on the steel surface, from the acrylic emulsion polymer, flame-retardant additives (ammonium polyphosphate, melamine, pentaerythritol), and flame-retardant fillers (TiO₂, Al(OH)₃). The experimental results showed that after 60-min fire resistance test under burning torch of 900–1000 °C, the backside temperature of coated steel was in the range of 200–250 °C. Addition of cenosphere into the acrylic polymer coating (at 2–10 wt%) enhanced its fire resistance performance by reducing the backside temperature of coated steels from 27 to 76 °C, as compared to the pure coating without FACs. Data from the furnace test showed that the presence of FACs in coating reduced its intumescent factor (from 14.9 to 33.5%) but produced the denser char layer with a better heat shielding ability. XRD analysis confirmed the interaction between cenosphere and coating matrices at high temperatures by forming the heat-stable compounds. TGA data demonstrated that increasing the content of FACs in coating increased its char weight residue at high temperatures and enhanced its thermal stability and fire resistance. Data from the mechanical test indicated that the presence of cenosphere in the acrylic polymer coating did not affect its hardness but decreased its adhesion to the steel surface (from 5.3 to 23.8%).

Graphical abstract