Construction of organophosphate-functionalized α‑zirconium phosphate towards fire-resistant, weather-resistant and antibacterial reinforcement of transparent fireproof coatings applied on wood substrates

To meet the requirements of fire protection and decorative properties of wood, developing transparent fireproof coatings with excellent comprehensive performance is vital. A new category of organophosphate-grafted α‑zirconium phosphate (α-ZrP) was synthesized as functional flame retardant, then in combination with melamine-formaldehyde resin prepared comprehensive transparent fireproof coatings covering fire protection, smoke suppression, anti-bacteria and weatherability. The results show that adding α-ZrP results in an effective improvement of the mechanical properties, fire protection and smoke suppression under the premise of guaranteeing the high transparency of the coatings. In particular, the MZrPPB3 sample containing a 98:2 mass ratio of phosphate ester to modified α-ZrP possesses 55.2 %, 76.2 % and 23.7 % decrement in flame spread rating, smoke density rating and equilibrium backside temperature at 900 s in comparison with MZrPPB0 sample without α-ZrP, respectively, accompanied by superior adhesion classification of 4B rating and pencil hardness of 2H rating. The efficient fire protection performance of α-ZrP-containing coatings attributes success to the high-quality intumescent char formed by the stable crosslinking and aromatic structures, as confirmed by characterization of FTIR and SEM-EDS analyses. Additionally, adding α-ZrP into the coatings confers them extraordinary weatherability rich in appearance integrity and fire protection performance after accelerated aging test. Meantime, the obtained satisfactory antibacterial property of coatings relates to the presence of α-ZrP with an antibacterial rate of up to 99.0 % for MZrPPB3 against Escherichia coli.