Abstract
Intumescent coatings are commonly used as passive fire protection systems for steel structures. The purpose of this work is to explore whether these can also be used effectively on glass fibre-reinforced epoxy (GRE) composites, considering the flammability of the composites compared to non-flammable steel substrate. The thermal barrier and reaction-to-fire properties of three commercial intumescent coatings on GRE composites have been studied using a cone calorimeter. Their thermophysical properties in terms of heating rate and/or temperature dependent char expansion ratios and thermal conductivities have been measured and correlated. It has been suggested that these two parameters can be used to design coatings to protect composite laminates of defined thicknesses for specified periods of time. The durability of the coatings to water absorption, peeling, impact, and flexural loading were also studied. A strong adhesion between all types of coatings and the substrate was observed. Water soaking had a little effect on the fire performance of epoxy based coatings. All types of 1 mm thick coatings on GRE helped in retaining ~90% of the flexural property after 2 min exposure to 50 kW/m2 heat flux whereas the uncoated laminate underwent severe delamination and loss in structural integrity after 1 min.
Highlights
Fiber-reinforced polymeric composites for structural applications are required to conform to specific fire performance requirements and to retain their mechanical integrity after exposure to heat/fire
The thermal barrier efficiency of intumescent coatings on steel structures is usually evaluated from temperature-time curves obtained from thermocouples embedded on the unexposed surface of steel plate in fire tests and determination of the “time to failure” in terms of time to reach a given temperature, defined by a specific test [7,8]
The results have demonstrated that the thermal barrier effectiveness of the intumescent coatings depends upon the degree of expansion and the thermal conductivity of the expanded char
Summary
Fiber-reinforced polymeric composites for structural applications are required to conform to specific fire performance requirements and to retain their mechanical integrity after exposure to heat/fire. Intumescent coatings are designed to expand to form an insulating and fire resistant charred barrier between the fire and the underlying substrate. This char protects the underlying structure, acting as a thermal insulator/barrier against flame and heat by physically stopping the heat and oxygen to penetrate the materials. The thickness, coherence and porosity of the char determine its thermal barrier efficiency [1,2] These coatings are available as solvent-based or water-based systems, which can be applied in an economical and simple way, such as by spray, brush or roller, onto several materials including metallic materials, polymers, textiles and wood. The rate and degree of char expansion depends upon many factors such as heating conditions, type of binder, solvent used, and any other additive or primer used for binding the coating to the substrate
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