Fire retardancy, epoxy formulation

In electronic encapsulation applications, epoxy derivatives of novolacs containing meta-bromo phenol have exhibited substantially better physical and performance properties compared to the conventional tetrabromo bisphenol-A epoxies and brominated epoxy novolacs. The meta-bromo phenol moiety contributes the expected improvements in thermal and hydrolytic stability to the formulation while providing fire retardancy properties (13). 

Structural panels with outer facings, skins, fire retardants, and cores with foam are glued with EPI adhesives [1,4]. Well formulated EPI adhesives have shown very good wetting and adhesion properties to metals and due to the good processing properties EPI adhesives have taken over some of the epoxy, urethane and cross-linked PVAc markets [1], especially in the USA. 

For some non-fire retardant grades of polymers, fire retardancy characteristics might improve when a filler is incorporated into the formulation. Thus, for epoxy resins, the incorporation of minerals, glass fibre, silica or graphite all improve flame spread, flammability and LOI from the poor category for the virgin polymer to the good... 

Chlorinated fire retardants (CFRs) are utilised in polyamides, epoxies and PBT. The use of mixed synergists, that is antimony oxide plus another synergist, can lower the total loading of FR additives to the formulation. With glass-filled polyamide compounds where a higher processing temperature is sometimes required, the elimination of antimony oxide greatly improves the thermal stability of the formulations. 

A flame retardant two component, low density epoxy filler paste for room temperature cure and specially formulated for use as an edge filler in honeycomb sandwich constructions where the fire properties of the filled panel edges may affect the fire retardancy rating of the component. 

The use of this simple correlation as the basis of a novel predictive combustion module, linked to the Henderson model, has been presented recently by McCarthy et al. [58], within a novel finite difference code which achieves good predictivity of both the plaque temperature and mass loss of an epoxy/E-glass composite under an imposed asymmetric heat load of 50 kW/m in a standard cone calorimeter experiment (Figure 14.4). This is despite the fact that the gas-phase combustion has been simplified as that of pure methane, when in reality a more complex gas mixture is released by most epoxy resin formulations, before accounting for any volatile emissions from included fire-retardants. 

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