Synergistic effect of clam shell bio-filler on the fire-resistance and char formation of intumescent fire-retardant coatings

Abstract

Clamshell (CS) bio-filler derived from clam shells was produced and then applied as a synergist in waterborne intumescent fire-retardant coatings. Fire protection and smoke density tests show that the combination of CS bio-filler and intumescent flame retardant (IFR) exhibits excellent synergistic effect on reducing the flame spread index (FSR), char index, weight loss, equilibrium backside temperature and smoke density rating (SDR) of the intumescent coatings. Especially, the FC-3 sample containing 52 wt% IFR and 3 wt% CS bio-filler exhibits the lowest FSR and SDR values, which are 68.3% and 37.3%, respectively, lower than those of FC-0 sample with 55 wt% IFR. The results from the accelerated ageing test show that the combination of IFR and CS imparts super durability of smoke suppression and flame-retardant properties to the intumescent coatings, exhibiting excellent anti-ageing properties. Char residue analysis demonstrates that the FC-3 sample containing 3 wt% CS bio-filler shows higher mass ratios of O/C, N/C and P/C than those of FC-0 without CS bio-filler, indicating more P, N and O-containing cross-linking structures remained in the FC-3 char, thus imparting high char-forming ability and thermal stability to the coatings, as supported by the results of thermogravimetric (TG) analysis and Fourier transform infrared spectroscopy (FTIR) analysis.