A facile strategy to construct ZnO nanoparticles reinforced transparent fire-retardant coatings for achieving antibacterial activity and long-term fire protection of wood substrates

To satisfy the fire requirement of wood structure buildings, waterborne transparent fire-retardant coatings with multi-function properties is necessary for practical application. A novel waterborne transparent fire-retardant coating was fabricated using organophosphate-grafted nano-ZnO as a multifunctional flame retardant. Adding ZnO nanoparticles greatly strengthens the mechanical property, smoke suppression property and fire protection performance of the coatings for wood substrates while keeping high transparency. Particularly, when the mass ratio of phosphate ester to nano-ZnO is 95:5, the resulting MZPPB3 sample shows the lowest smoke density rating value of 2.1% and flame spread rate value of 7.2% among the samples, concomitant with a high transparency of 84.5%. Besides, the uniform distribution of ZnO nanoparticles has a super shielding effect on reducing ageing degradation of the coating structure, thus endowing excellent durable fire protection performances to the coating sample. Furthermore, nano-ZnO has an excellent inhibiting effect on E. coli and S. aureus colonies in the coating, and the antimicrobial activity indexes against E. coli and S. aureus of MZPPB3 coating reach 96.5% and 99.3%, respectively.