Correlations between pyrolysis combustion flow calorimetry and conventional flammability tests with halogen‐free flame retardant polyolefin compounds

Abstract

SUMMARYSeven halogen-free flame retardant (FR) compounds were evaluated using pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry. Performance of wires coated with the compounds was evaluated using industry standard flame tests. The results suggest that time to peak heat release rate (PHRR) and total heat released (THR) in cone calorimetry (and THR and temperature at PHRR in PCFC) be given more attention in FR compound evaluation. Results were analyzed using flame spread theory. As predicted, the lateral flame spread velocity was independent of PHRR and heat release capacity. However, no angular dependence of flame spread velocity was observed. Thus, the thermal theory of ignition and flame spread, which assumes that ignition at the flame front occurs at a particular flame and ignition temperature, provides little insight into the performance of the compounds. However, results are consistent with a heat release rate greater than about 66 kW/m 2 during flame propagation for sustained ignition of insulated wires containing mineral fillers, in agreement with a critical heat release rate criterion for burning. Mineral fillers can reduce heat release rate below the threshold value by lowering the flaming combustion efficiency and fuel content. A rapid screening procedure using PCFC is suggested by logistic regression of the binary (burn/no-burn) INTRODUCTIONTesting of flame retardant (FR) materials presents technical and scientific challenges. Various enduse applications have unique fire tests, which in most cases have not been correlated to small-scale methods of flammability assessment. To complicate matters further, these tests are often conducted on finished articles rather than pure polymer compounds. Limiting oxygen index (LOI) and cone calorimetry are among the most commonly cited methods for assessing flammability of FR polymer compounds. Although studies have raised questions about the reliability of LOI in flammability research [1, 2], LOI remains one of the most popular flammability test methods. This is likely due in large part to the fact that measurement of LOI can be done quickly using relatively inexpensive and simple equipment. Despite its popularity, correlation of LOI with performance in industry flame tests is limited, and application to predict burn behavior in actual fires is uncertain [3].Cone calorimetry is another method for flammability assessment of materials, and can be run on raw materials as well as fabricated articles, providing a wealth of data from measurement of a single specimen. While cone calorimetry is steadily gaining in popularity, its use outside of research remains limited due to a number of factors, including the high cost, complexity of cone calorimeters, and the resources required to operate and maintain them. Additionally, there is no widespread agreement in the industry about which parameters are most meaningful. Therefore, more studies correlating burn performance in key industry tests with results of cone calorimetry on compounds are needed.Cone calor...

Study on intumescent flame retarded polystyrene composites with improved flame retardancy

“…Layered α-zirconium phosphate (ZrP) is an alternative nanoplatelet to montmorillonite clay for developing the preliminary structure-property relationship of polymer/layered inorganic nanocomposites, since ZrP has exchangeable cations, narrow particle size distribution and controllable aspect ratio [18], [19], [20], [23], [24], [25] and [26]. In this work, ZrP was synthesized by refluxing zirconyl chloride (ZrOCl2·8H2O, 98%, Aldrich) in 10 mol/L phosphoric acid (H3PO4, ≥85%, solution in water, A.C.S.…”

“…Led by the National Institute of Standards and Technology (NIST), apparatus such as the radiant Panel Apparatus and Rapid Cone Calorimetry have been developed to acquire the critical fire parameters [12], [13], [14] and [15]. Besides these, pyrolysis combustion flow calorimetry, also known as microscale combustion calorimetry (MCC), has been developing as a new tool to screen for flammability of polymeric materials [16], [17], [18] and [19]. The correlation between MCC and other evaluation methods, such as cone calorimetry, limiting oxygen index (LOI), and vertical burning tests, has been good in some cases.…”

Pyrolysis Combustion Flow Calorimetry Studies on Some Reactively Modified Polymers

“…Pyrolysis Combustion Flow Calorimetry (PCFC), also known as micro-scale combustion calorimetry, was shown to be a very valuable small-scale technique for screening flammability of different materials in recent years [1]. We have chosen PCFC for our studies as a rapid screening technique as it only requires a few milligrams of a polymer for testing, and often provides a wealth of combustion-related data.…”

“…In the present study, the operational conditions were in conformance with the test method A. This method also is an established ASTM standard for testing flammability characteristics of solid materials [1]. PCFC is capable to measure the following parameters: peak to heat release rate (PHRR); temperature at peak heat release rate (TPHRR); total heat release (THR); heat release capacity (HRC) and a percentage of the char residues.…”

Polymer Combustion as a Basis for Hybrid Propulsion: A Comprehensive Review and New Numerical Approaches

“…Each sample is run in triplicate and the data obtained are averaged over the three measurements [12]. The instrument also generates plots of the Heat Release Rates (HRR) against the temperature and gives values for the maximum amount of heat released per unit mass per degree of temperature (i.e., heat release capacity measured in Jg −1 K −1 ), the latter being a reliable indicator regarding flammability of a material (Table 3).…”