Fire performance heat release

Accuracy of Oxygen Consumption Method. We have demonstrated that the oxygen consumption method can be used to quantify the amount of heat contributed to the fire environment by the walls. The heat release rate can be used as a diagnostic tool to evaluate performance of assemblies in question. 

The versatility and accuracy of the oxygen consumption method in heat release measurement was demonstrated. The critical measurements include flow rates and species concentrations. Some assumptions need to be invoked about (a) heat release per unit oxygen consumed and (b) chemical expansion factor, when flow rate into the system is not known. Errors in these assumptions are acceptable. As shown, the oxygen consumption method can be applied successfully in a fire endurance test to obtain heat release rates. Heat release rates can be useful for evaluating the performance of assemblies and can provide measures of heat contribution by the assemblies. The implementation of the heat release rate measurement in fire endurance testing depends on the design of the furnace. If the furnace has a stack or duct system in which gas flow and species concentrations can be measured, the calorimetry method is feasible. The information obtained can be useful in understanding the fire environment in which assemblies are tested. 

The main reason for this is that the products concerned have good fire performance. They have very low heat release characteristics, so that they do not add significantly to the energy of the fire and, furthermore, will not spread flame in the absence of an external energy source, so that they hardly increase the fuel supply for the fire. 

Heat release rate is another relevant measure of the combustibility of a material along with ease of ignition and flame spread. Smith (55) points out that the release rate data, obtained under different test exposures, will be useful in predicting the performance in actual fires under different fuel loading. Release rate data can thus be used—along with other... 

Note FPI, fire performance index (m2 s/kW) RHR, rate of heat release (kW/m2) SEA, smoke extinction area (m2/kg) SP, smoke parameter (MW/kg) TTI, time to ignition (s). 

There has been a great recent market demand for halogen-free fire-retardant polymers. Zinc borates are also multifunctional fire retardants in halogen-free polymers. They can promote char formation, reduce the Rate of Heat Release, smoke evolution, carbon monoxide generation, and afterglow combustion. When used in conjunction with metal hydroxides, they can also display synergy in fire test performance. 

The impact of the nanocomposite technology on polymers is huge, reflected in enhanced properties of the resulting PNs, such as enhanced mechanical, barrier, solvent-resistant, and ablation properties.12 The effect of nanocomposite technology on the thermal and fire performance of the polymers is primarily observed in two important parameters of the polymers (1) the onset temperature (7( ,nsct) in the thermogravimetric analysis (TGA) curve—representative of the thermal stability of the polymer, and (2) the peak heat release rate (peak HRR) in cone calorimetric analysis (CCA)—a reflection of the combustion behavior (the flammability) of the polymer. The Tonset will be increased and the peak HRR will be reduced for a variety of polymers when nanoscale dispersion of the nanoadditive is achieved in the polymer matrix. 

The nanodispersed nanoadditives usually show enhanced fire performance and CCA has been the most powerful tool in analyzing the flammability of the PNs. In most cases, the PNs, as seen in Figure 11.20, show a significantly reduced peak HRR in the CCA curve. More examples of this are seen in PA-6/clay nanocomposite, which shows a 63% reduction in the peak HRR at 5% loading (Figure 11.2898 in which the heat release rate as a function of time for pure PA-6 and its clay nanocomposites is shown) and in poly(ethylene-co-vinyl acetate) (EVA)/clay nanocomposite,99 which shows a reduction of the peak HRR at about 50% at 5% organoclay loading. 

Often it is very difficult to determine the burning behavior of complex objects on the basis of the performance of its individual components in bench-scale reaction-to-fire tests. It is much more practical to measure the heat release rate and related properties for the complete object. This requires a large-scale test. In other cases, it is not possible to capture certain aspects of real fire behavior such as melting, delamination, joint effects, etc., in a bench-scale test. A large-scale test is needed to assess these effects. Two commonly used large-scale reaction-to-fire tests are test methods are discussed as follows. 

Fire testing was performed according to 14 CFR Part 25 for heat release rate (HRR), smoke density, and flame resistance [22], HRR was measured using retaining wires on the sample holder in an attempt to prevent melt dripping. At least two samples were tested and averaged to obtain reported values. 

FIGRA, fire growth rate THR600s, total heat release LFS, lateral flame spread SMOGRA, smoke growth rate TSP600s, total smoke production F flame spread FIPEC, Fire Performance of Electric Cables (Reference 105). 

In the early 1980s, Vytenis Babrauskas, at the NIST (then NBS), developed a more advanced test method to measure RHR the cone calorimeter (ASTM E 1354).71164 This fire test instrument can also be used to assess other fire properties, the most important of which are the ignitability (as discussed earlier), mass loss, and smoke released. Moreover, results from this instrument correlate with those from full-scale fires.165-170 To obtain the best overall understanding of the fire performance of the materials, it is important to test the materials under a variety of conditions. Therefore, tests are often conducted at a variety of incident heat fluxes. The peak rates of heat release (and total heat released) of the same materials shown in Table 21.15 at each incident flux, are shown in Table 21.16.147... 

ASTM E 84 Steiner tunnel test, thus generating more useful results. Figure 21.13 shows a room-comer test layout. The cone calorimeter fire-performance index (with tests conducted at 50kW/m2)179 was shown to be a good predictor of time to flashover in FAA full aircraft fires170 180 and in the ISO 9705 room-corner test.181 In addition, the same cone calorimeter tests, but using only heat release criteria, have been shown to have almost perfect predictability of ISO 9705 room-comer test rankings.181... 

Propensity of flashover The ratio of ignition time to peak rate of heat release. It is the same as fire performance index iirs/kW... 

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