Flammability heat release rate

The flammability of solids may be considered to be a function of the heat release rate and critical ignition energy of the material being studied. Flammability is an inverse function of the actual ignition energy of the material in question, and it is directly related to the rate of heat liberated after ignition of the sample. 

A.L. Bridgman and G.L. Nelson, Heat Release Rate Calorimetry and Engineering Plastics, J. Fire and Flammability. 12 114 (1982). 

Fire hazard is a combination of several properties, including ignitability, flammability, flame spread, amount of heat released, rate of heat release, smoke obscuration and smoke toxicity. 

Fire safety in a particular scenario is improved by decreasing the corresponding level of fire risk or of fire hazard. Technical studies will, more commonly, address fire hazard assessment. Fire hazard is the result of a combination of several fire properties, including ignitability, flammability, flame spread, amount of heat released, rate of heat release, smoke obscuration and smoke toxicity. 

The heat generated in a fire is due to various chemical reactions, the major contributors being those reactions where CO and COg are generated, and O2 is consumed, and is defined as the chemical heat release rate (3). Techniques are available to quantify chemical heat release rate using FMRC s Flammability Apparatus (2-6), Ohio State University (OSU) Heat Release Rate Apparatus (J 3) and the NIST Cone Calorimeter (J jO. Techniques are also available to quantify the convective heat release rate using the FMRC Flammability Apparatus (2, 3) and the OSU Heat Release Rate Apparatus (J 3) The radiative heat release rate is the difference between the chemical and convective heat release rates (2,3). In the study, FMRC techniques were used. 

Techniques are available to quantify the generation of smoke, toxic and corrosive fire products using the NBS Smoke Chamber (15), pyrolysis-gas chromatography/mass spectrometry (PY-GC-MS) (J 6), FMRC Flammability Apparatus (2,3,5,17,18), OSU Heat Release Rate Apparatus (13) and the NIST Cone Calorimeter (JJO. Techniques are also available to assess generation of 1) toxic compounds in terms of animal response (19), and 2) corrosive compounds in terms of metal corrosion (J 7). In the study, FMRC techniques and AMTL PY-GC-MS techniques were used. 

Mass Loss Rate as a Function of External Heat Flux. The technique for the measurement of mass loss rate as a function of heat flux was developed in 1976 at FMRC using the Small-Scale Flammability Apparatus (8 ). Several other flammability apparatuses are now available for such measurements, such as OSU Heat Release Rate Apparatus (13) and NIST Cone Calorimeter (1 4). 

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. 

Tewarson, A., Heat release rates from burning plastics. Journal of Fire and Flammability 1977, 8, 115-130. 

Requirements for upholstered furniture flammability exist in various states, including California, based on California Technical Bulletin 133 (CA TB 133),91 which was also made into a consensus standard by ASTM committee E05 as ASTM E 1537.92 The gas burner used as the ignition source in CA TB 133 is a square-shaped burner that applies propane gas for 80s at a flow rate of 13L/min. The test is severe enough that it can usually not be met, unless the foam contained in the upholstered furniture item is flame-retarded. The pass/fail criteria are a peak heat release rate of 80 kW and a total heat released that does not exceed 25 MJ over the first 10 min of the test. In California, moreover, all foam contained within upholstered furniture must be flame-retarded to comply with CA TB 117. Moreover, the IFC and NFPA 101 both have parallel requirements to those discussed earlier for mattresses. In other words, the 2006 editions of both the codes contain requirements that upholstered furniture items in health care occupancies as well as detention and correctional occupancies that are not sprinklered must comply with a peak heat release rate of 250kW and a total heat release of no more than 40 MJ in the first 5 min of the test, when tested to ASTM E 1537 (or CA TB 133). However, the 2007 edition of the IFC and the 2009 edition of NFPA 101 lowered these values to 80 kW and 25 MJ over 10 min. Finally, the IFC 2007 added college and university dormitories to the list and eliminated the sprinkler exception for detention occupancies. 

Subsequently, the ignition temperature and the HRC parameter can be determined and used to compare PCFC data with data from other test methods. The HRC is defined as the ratio of the heat release rate and the heating rate. The peak heat release rates determined in cone calorimeter experiments correlate well with peak HRC data from PCFC experiments. In terms of other tests, results from the LOI (ASTM D 2863) test method exhibit a reciprocal correlation with HRC values, while HRC can also be a rough indicator for UL 94 ratings. In approximate terms, it has been said that HRC results can classify materials into three ranges of material flammability, as follows ... 

Cone calorimetry according to the ASTM E1354138 or ISO 5660139 standards are commonly used in the laboratory to screen flammability of materials by measuring heat release characteristics of the compound.116140 This device is similar to FPA but does not have the versatility of FPA. The cone calorimeter can determine the ignitability, heat release rates, effective heat of combustion, visible smoke, and C02 and CO development of cable materials. This test has been used extensively for wire and cable material evaluation. The microscale combustion calorimeter (MCC), also known as pyrolysis combustion flow calorimeter (PCFC), was recently introduced to the industry for screening heat release characteristics of FR materials.141142 This device only requires milligram quantities of test specimen to measure the heat release capacity (maximum heat release potential). Cone calorimetry and MCC have been used in product development for flammability screening of wire and cable compounds.118... 

FIGURE 26.6 Relationship between FIGRA and THR measured in MCC (i.e., PCFC). FIGRA = PHRR/ TTPHRR, FPI = TTI/PHRR, where PHRR is peak heat release rate, TTPHRR is time to peak heat release rate, and TTI is time to ignition. (Based on Lin, T.S. et al., Correlations between microscale combustion calorimetry and conventional flammability tests for flame retardant wire and cable compounds, in Proceedings of 56th International Wire and Cable Symposium, 2007, pp. 176-185.)... 

Ethylene copolymers were compared with liquid plasticisers for use as additives to improve the flexibility of poly(vinyl chloride) (PVC) for electrical cable insulation applications. The PVCs were assessed by determining smoke generation, flammability, tensile properties and the low temperature brittle point. The ethylene copolymers gave similar peak heat release rates, but the peak smoke and the total smoke generation were lower. They also gave similar or increased strength, similar elongation and flexural modulus, and lower brittle point temperatures. 4 refs. 

Cone calorimetry was used to measure the effectiveness of the additives on reducing the flammability of PE the parameters available include the heat release rate and especially its peak value, the peak heat release rate (PHRR) and time to peak heat release rate (tPHHR) total heat release (THR) time to ignition (tig) average mass loss rate (AMLR) and average specific extinction area (ASEA), a measure of smoke formation. A decrease in the PHRR, THR, AMLR, and ASEA are desired along with an increase in tig and tPHRR. The heat release rate (HRR) curves as a function of time for pure PE and its nanocomposites are shown in Figure 4A and cone data are summarized in Table II. 

No differences in flammability characteristics between the 0.1% Cu20-treated and untreated flexible polyurethane foam were observed. These characteristics were examined to assure that the positive effect on toxicity was not contradicted by negative effects on the flammability properties. The flammability characteristics examined were (1) ignitability in three systems (the NIST Cup Furnace Smoke Toxicity method, the Cone Calorimeter, and Lateral Ignition and Flame Spread Test (LIFT)), (2) heat release rates under small-scale (Cone Calorimeter) and medium-scale (furniture calorimeter) conditions, (3) heats of combustion under small-scale (Cone Calorimeter) and medium-scale (furniture calorimeter) conditions, (4) CO/CO2 ratios under small-scale (Cone Calorimeter) and medium-scale (furniture calorimeter) conditions, (5) smoke obscuration (Cone Calorimeter), and (6) rate of flame spread (LIFT). 

Polymer clay nanocomposites exhibit very low flammability. For instance, the heat release rate during the combustion of polyamide 6-clay nanocomposite is reduced by 63% with a clay content of 5wt%. The nanocomposite structure also enhances the property of the char through reinforcement of the... 

Further research should be conducted toward establishing a better means to categorize the true fire hazard of all flammable and combustible liquids. The flash point, and in some cases boiling point, are measured values that are used for the current classification system. Additional properties, such as viscosity, dissolved combustible solids, and heat of combustion or heat release rate data should be included in a more comprehensive system. 

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