Development of Fibres Reinforced Intumescent Coatings for Mild Steel Structures

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Low performance and soft char of intumescent coatings (IC) are less effective for fire protection. In this research, epoxy-based IC control formulation was developed using ammonium polyphosphate, pentaerythritol, melamine at 3:1:1 ratio, with nine intumescent fillers. Compared to a market coating, the control developed higher char expansion with more residues in 800°C furnace fire test (FFT). TGA analysis confirmed its higher residual weight and lower degradation rate. This formulation was reinforced with fibres for improvement of char strength and fire performance. Fibre reinforced IC (FRIC) were developed with 10-mm long and 0.42 wt% glass fibre (GFRIC), carbon fibre (CFRIC), hybrid fibres (HFRIC), glass wool fibre (GWFRIC), Rockwool fibre (RWFRIC) and ceramic wool fibre (CWFRIC). All formulations were prepared by shear mixing, analyzed in TGA and FFT, characterized using SEM, EDX, XRD, and tested in 36 N char strength test and 3000 N compression test. Fire retardance performance by CFRIC revealed the lowest steel temperature at 127°C after an hour exposure to 1100°C. The fibres had raised TGA residue in the range of 0.8 – 6.8 wt% i.e. CWFRIC was the highest, 43 wt%. Similar trend was also evident in FFT. Optimum carbon content with rise of high temperature elements i.e. silicon, phosphorous, magnesium (Mg), aluminium (Al) and titanium were detected in FRIC coatings and chars. High temperature compounds found in FRIC chars included boron phosphate, boron oxide, silica, MgAl-hydrate and carbon. Fibres improved honeycomb-like char structure, became denser with enhanced strength between 15 – 83 % than control. Average stiffness of the FRIC chars; 1.39 – 3.26 MN/m was higher than 1.0 and 1.12 MN/m by control and commercial, respectively. Char morphology showed ‘bridging’ mechanism by the fibres with intumescents or char-bonded to strengthen the bond in coating and char. The chars were more insulative due to higher production of smaller micro-voids by the entangled fibres that trap air and cooling gaseous, prevented heat penetration and flame spread to substrate. In conclusion, reinforcement of 10-mm long and 0.42 wt% fire retardant fibres enhanced char strength and fire performance of IC formulations for protection of steel substrates.