Improving the fire retardancy of FRP composites

As shown in the previous section, most polymer composites used in construction involve highly flammable matrices, such as polyester, vinylester or epoxy resins. Besides, if glass and carbon fibres are generally considered heat resistant, other type of fibres used for specific applications may also exhibit poor fire behaviour (aramid, polyolefins or other polymer fibres, for instance). Therefore, to meet the safety requirements specified in building codes and 

Flame-retardant systems are intended to inhibit or to stop the combustion cycle of the polymer composite. After such a treatment, the material does not become non-combustible, but it is more resistant to ignition, takes more time to burn and generates less heat compared to the original composite. As a function of their nature, flame-retardant systems act either chemically or physically (Troitzsch, 2004 Horrocks and Price, 2001 Laoutid et al., 2009). They can interfere with the various processes involved in the combustion cycle (heating, pyrolysis, ignition and propagation stages) which were previously discussed in Section 12.4.1. 

Fire retardants may also operate physically, according to the following mechanism  

Fire retardants can be sorted in two main categories (1) additives which are generally incorporated during the manufacturing process and consist of 

A second type of filler, called active flame-retardant fillers, is considered more effective than inert particles. Its operating mode involves not only fuel dilution, but also an additional cooling or heat sink effect. Indeed, these compounds are able to decompose at elevated temperature via eudothermic reactions which absorb energy and tend to slow down thermal degradation of the composite. Besides, inert gases (water vapour, carbou dioxide) are formed by the filler decomposition and contribute to diluting the concentration of combustible volatiles in the flame-environment. Common active flame retardant fillers are  

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