Peak heat release rate epoxy nanocomposites

FIGURE 5.7 Total heat evolved plotted against FIGRA (peak heat release rate/time to peak heat release rate). Results are shown for an epoxy resin and epoxy resin/5 wt% D nanocomposite at various irradiances (30, 50, and 70 kW/m ). 

Thermal Decomposition of Polymeric Nanocomposites Based on Anionic Clays The thermal decomposition of DGEBA nanocomposites cured with polyoxypropylene diamine (Jeffamine D230) and containing 4-toluenesul-fonate/LDH was investigated by simultaneous thermal analysis (STA) in air. The LDH nanocomposite (TS/LDH) is compared to the neat epoxy and to a bis(2-hydroxyethyl)ammonium montmorillonite nanocomposite (30B). The clay content was 5 wt% for both nanocomposites. In Figure 9.24, differential thermal analyses obtained by STA are shown. A main exothermic peak is observed at about 550° C for neat epoxy. In the LDH nanocomposite this peak is split in two parts, so the heat release rate is decreased and the heat evolution delayed, where as no relevant difference is observed between neat epoxy and the cationic clay nanocomposite. 

A typical heat release rate curve for a neat epoxy system and the respective layered silicate nanocomposite, is shown in Fig. 2.12. Both peak and average heat release rate, as well as mass loss rates, are all significantly improved through the incorporation of the nanopartieles. In addition, no increase in specific extinction area (soot), CO yields or heat of combustion is noticeable. However, the mechanism of improved flame retardation is still not clear and no general agreement exists as to whether the intercalated or exfoliated structure leads to a better outcome. The reduced mass loss rate occurs only after the sample surface is partially covered with char. The major benefits of the use of layered silicates as a flame retardation additive is that the filler is more environmentally-friendly compared to the commonly used flame retardants and often improves other properties of the material at the same time. However, whilst the layered silicate strategy is not sufficient to meet the strict requirements for most of its application in the electrical and transportation industry, the use of layered silicates for improved flammability performance may allow the removal of a significant portion of conventional flame retardants. 

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