Simmonds, H., Cox, S., Nicholls, S., and Williams, G., "The Use of Intumescent Coatings with Polymer Composites for High Temperature Automotive Applications," SAE Technical Paper 2015-01-0713, 2015, doi:10.4271/2015-01-0713.
To meet corporate CO2 emission targets polymer composites are being explored for light-weighting vehicle applications. Operational requirements may demand that such materials function above glass transition temperatures or heat deflection points. Intumescent coatings are traditionally used in construction to protect steelwork during fire. This paper presents a novel experimental investigation of two intumescent technologies to thermally protect a reinforced polyamide, for use as a semi-structural vehicle component.Coatings were assessed against the thermal requirement to withstand 500°C for 10 minutes. The differences in performance observed between water and epoxy based coatings as well as when an insulation layer was introduced are reported.Ultimate Tensile Stress (UTS) and modulus values were obtained at −40°C, ambient, and 85°C for uncoated specimens before and after thermal cycling. Results indicated although samples did not surpass the heat deflection point of the material (220°C), exceeding the glass transition temperature led to a reduction in mechanical properties.Considering electrified vehicles it may be beneficial if materials are electrically resistant Therefore, the surface and through-thickness resistivity of uncoated and coated plaques was measured. The resistance of coated samples before and after thermal cycling exceeded the threshold of 1×106Ω, however, when coated samples were environmentally pre-conditioned, these materials failed to meet the required surface resistance.There are a number of parameters that need to be understood: light-weighting, electrical resistance, thermal protection, and manufacturing demands for automotive structures; this work demonstrates the potential of selected intumescent coating technologies to provide a balance between the protection of composite performance while achieving light-weighting targets for high temperature automotive applications.