Comparative Study of Fire Resistance and Char Formation of Intumescent Fire-Retardant Coatings Reinforced with Three Types of Shell Bio-Fillers

Three types of shell bio-fillers, including eggshell (CES), conch shell (CHS) and clamshell (CMS), were prepared by cleaning, ultrasonication and pulverizing processes of biowastes, and then applied to intumescent fire-retardant coatings. The effects of shell bio-fillers with different polymorphs on the fire resistance and char-forming of intumescent fire-retardant coatings were investigated by cone calorimeter test, fire protection tests, smoke density test, thermogravimetric analysis (TG), and the fire resistance and char-forming mechanism of bio-fillers in intumescent fire-retardant coatings were proposed. The results show that three kinds of bio-fillers exert an excellent synergistic effect on enhancing the fire resistance and char-forming properties of the intumescent fire-retardant coatings, while clamshell has the best synergistic efficiency among the bio-fillers. Especially, IFRC-CMS coating containing 3 wt% clamshell shows the best fire protection performance and lowest smoke production and heat release, which offers an equilibrium backside temperature of 134.6 °C at 900 s, a flame-spread rating of 14.4, and a smoke density rating value of 22.8%. The synergistic efficiency of bio-fillers in the intumescent coatings depends on the polymorphs of CaCO(3) in bio-fillers, and aragonite CaCO(3) shows a higher synergistic efficiency compared to calcite CaCO(3) and the mixture of aragonite and calcite CaCO(3). The CMS composed of aragonite shows the best synergistic effect, CHS composed of aragonite and calcite comes second, and CES composed of calcite has the weakest synergistic effect.