Unsaturated polyester resins are used extensively in fibre-reinforced composites and coatings because of their relatively low cost, good processability and balance of properties. Worldwide consumption of unsaturated polyester resin is over 1.6million tonnes per year and it accounts for over 90% of the fibre-reinforced composites market. However, one major disadvantage of these resins is their flammability - they ignite readily, burn vigorously and generate dense smoke during combustion. The fire performance of polyester resins can be improved by using fire-retardant additives, the most common being halogenated compounds containing chlorine or bromine, antimony-based systems and non-combustible fillers including aluminium trihydrate. However, halogenated systems generate large quantities of toxic and corrosive combustion products so tend to perform poorly in modern, more stringent tests developed, in particular for the rail industry (e.g. Epiradiateur F, CEN/TS 45545-2, Single Burning Item SBI test to EN 13823). There is a growing trend towards halogen-free additives such as alumina trihydrate (ATH) and ammonium polyphosphate (APP), the use of which is predicted to grow up to 10% per year to 2016. However, these additives must be used at high loadings to achieve a significant effect (up to 60% by weight) which reduces processability, reduces strength and impact resistance and increases weight.

In general, coatings for improving fire performance fall into two categories –fire retardant coatings, which reduce the surface spread of flame, and fire resistant coatings (including intumescent systems), which protect the underlying substrate from a fire. Intumescent coatings form a stable, expanded char barrier which prevents heat from reaching the substrate, and fuel gases escaping from the substrate to feed the flame, thus enabling the structure to withstand the fire for a longer period of time. Fire retardant coatings are commonly used to prevent/delay ignition of the substrate and reduce the surface flame spread. Common resins include polyurethanes and alkyds and they generally contain halogenated compounds and antimony trioxide.

Unsaturated polyester coatings are commonly used in the fibre-reinforced composites industry to provide colour, gloss, weathering resistance and fire resistance. Fire-retardant products most commonly used halogen-based or antimony-based additives although, as described previously, these have significant disadvantages in terms of health. Some ATH-filled systems are available but these are generally less robust, more brittle, less impact resistant and less scratch resistant than their halogenated counterparts. There is a gap in the market for high-performance, fire retardant polyester coatings, particularly halogen-free systems, which can work as a fire retardant coating independently or as part of a package with a fire-retardant substrate.