Fabrication of organophosphate-grafted kaolinite and its effect on the fire-resistant and anti-ageing properties of amino transparent fire-retardant coatings

Abstract In this work, a series of organophosphate-grafted kaolinite flame retardants (KPPBs) were fabricated via grafting flexible phosphate ester (PPB) on the surface of kaolinite (Kaol), and the chemical structure of KPPBs was characterized in detail. Afterward, the obtained KPPBs were blended with amino resin to prepare transparent fire-retardant coatings. The results indicate that the KPPBs endow the resulting coatings with a high light transmittance due to the uniform distribution of Kaol in the amino matrix. The results of combustion behavior indicate that the addition of Kaol greatly enhances the fire protection and smoke suppression properties of the transparent coatings, exhibiting superior synergistic flame retardant and smoke suppression effect. Especially, when the weight ratio of PPB and Kaol is 95:5, the fabricating MKPPB3 coating acquires the best synergistic effect, and the flame spread rating and smoke density rate values are decreased by 64.9% and 45.0%, respectively, compared to those of MKPPB0 coating without Kaol. The superior synergistic effect of Kaol in the coatings is ascribed to the formation of more thermally stable cross-linking structures and aromatic structures that generate a high-quality intumescent char against the fire, as supported by FTIR and SEM analyses. TG analysis shows the addition of Kaol can strengthen the thermal stability and char-forming of the coatings, and the residual weight of MKPPB3 at 800°C increases to 31.9%. The results of accelerated ageing test indicate that the incorporation of Kaol can weaken the blistering and powdering phenomenon, thus endowing superior durability of integrity and fire protection to transparent coatings.