Pyrolysis-combustion flow calorimetry

FIGURE 26.4 Probability for flame spread versus heat release capacity of compounds. (Cogen, J.M. et al., Correlations between pyrolysis combustion flow calorimetry and conventional flammability tests with halogen free flame retardant polyolefin compounds, Fire Mater., 2009, 33, 33-50.)... 

Lyon, R.E. and Walters, R.N., Pyrolysis combustion flow calorimetry, J. Anal. Appl. Pyrolysis, 2004, 71, 27-46. 

Zhang and co-workers [78] studied the decomposition and flammability of fire retarded UV visible sensitive polyacrylates and their copolymers based on bisphenol A (BPA), l,l-dichloro-2,2-bis(4-hydroxylphenyl)ethylene (BPCII) and 4,4 -dihydroxy-3-ethoxy benzylidenoacetophenone polyarylate (Chakon II). The study included investigation by Py-GC-MS, simultaneous thermal analysis and pyrolysis-combustion flow calorimetry [59]. 

Thermal relationships between flammability and structure/composition of these polymers was explored. It is found that BPC Il-polyarylate is an extremely fire-resistant thermoplastic that can be used as an efficient flame-retardant agent to be blended with the other polymers. Chakon Il-polyarylate is of interest as a UV/visibk-sensitive polymer with a relatively low HRR and a high char yield. Pyrolysis combustion flow calorimetry (PCFC) results show that the total heat of combustion of the copolymers or blends changes linearly with the composition, but the change of maximum HRR and char yield depends greatly on the chemical structure of the components. 

Fire calorimetry (4,11,20,25) (see under Testing to Obtain Engineering Data) is used to obtain HRP as the slope of heat release rate versus external heat flux or as the ratio x c°/Dg = HOC/Lg, from individual measurements. Table 7 contains HOC and x (=HOC//ic°) for common polymers while HRP are listed in Table 8. The heat of combustion of the fuel gases, hc, was measured separately in a pyrolysis-combustion flow calorimeter (26) (see section on The Pyrolysis-Combustion Flow Calorimetry). 

Experimental values for hc° determined by pyrolysis-combustion flow calorimetry (see below) are listed in Table 7. The elemental analysis of chars gives typical chemical formula C5H2 from which the heat of combustion of the char calculated from oxygen consumption is /ic,p° 37 kJ/g, which can be used to estimate the heat of combustion of the fuel gases of charring polymers using equation 56 if /x is known. 

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... 

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