Combustion and Flame 162 (2015) 4660–4670 Contents lists available at ScienceDirect Combustion and Flame journal homepage: www.elsevier.com/locate/combustfame Measurement of heat release in laminar diffusion flames fueled by controlled pyrolysis of milligram-sized solid samples: Impact of bromine- and phosphorus-based flame retardants Fernando Raffan-Montoya a , Xi Ding a , Stanislav I. Stoliarov a,∗ , Roland H. Kraemer b a University of Maryland, Department of Fire Protection Engineering, College Park, MD, USA b Advanced Materials and Systems Research, BASF SE, Ludwigshafen, Germany article info Article history: Received 29 June 2015 Revised 23 September 2015 Accepted 25 September 2015 Available online 20 October 2015 Keywords: Polymer flammability Heat of combustion Combustion efficiency Flame inhibitors Oxygen consumption calorimetry Milligram-scale flame calorimeter abstract Brominated flame retardants (BFRs) are widely used in polymers due to their high effectiveness at relatively low cost. Recent studies suggest that certain BFRs may present health and environmental hazards, yet ob- taining adequate replacements is an ongoing challenge. To develop new additives, it is of paramount impor- tance to better understand the mechanisms governing the action of flame retardants in polymers, particularly their action in the gas phase, and to develop effective screening techniques for potential candidates. To ad- dress this challenge, a novel apparatus, the Milligram-scale Flame Calorimeter (MFC), is proposed. In MFC, the pyrolysis and gas-phase combustion processes are uncoupled. Samples of 35 ± 5 mg are pyrolyzed in an anaerobic atmosphere and their pyrolysis products are burned in a laminar, near axisymmetric diffusion flame under controlled and customizable conditions in a fully enclosed system. Heat release information is obtained through the oxygen consumption calorimetry. The masses of post-combustion pyrolysis residue and solid particulate combustion products (e.g., soot) are measured. In this manuscript, a description of the design, parametric optimization of test conditions, and overall testing methodology is given. Heat release measurements are presented for polystyrene with increasing amounts of brominated polystyrene as well as poly(butylene terephthalate) with increasing concentrations of aluminum diethylphosphinate and results are compared to the Cone Calorimetry (Cone) and Microscale Combustion Calorimetry (MCC) measurements conducted on the same materials. Using combustion efficiency as a metric, the sensitivity to both bromine and phosphorus gas-phase activity is determined. The impact of these flame retardants is pronounced in the Cone experiments and largely undetected by the MCC. The MFC shows trends with respect to the flame retar- dant content comparable to the Cone. However, the absolute values of MFC combustion efficiencies tend to be notably higher that those observed in the Cone experiments. Overall, the MFC results demonstrate that this novel apparatus can be used to detect gas-phase activity of flame retardants using milligram-sized samples. © 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved. 1. Introduction and background While offering highly customizable mechanical properties, rela- tively low mass, and streamlined processing, most commercial poly- mers also possess inherent flammability that limits their applicabil- ity. Over the years, a variety of flame retardant additives has been introduced to address this flammability problem. These flame re- tardants can interfere with the pyrolysis and combustion processes through both physical and chemical mechanisms, and may act in the condensed phase, gas phase, or both. Among these additives, bromi- nated flame retardants (BFRs) have become ubiquitous due to their high effectiveness at relatively low cost. However, as data on their ∗ Corresponding author. E-mail address: stolia@umd.edu (S.I. Stoliarov). use and behavior over time have been compiled, it has been shown that some BFRs present environmental hazards due to their bioaccu- mulation and persistence in the environment among other reasons [1,2]. Industry is shifting towards suitable replacements [3], but the process is not trivial and testing potential replacements can be costly. Understanding the mechanisms of action of BFRs is necessary to develop adequate replacements. Over the past five decades, a signifi- cant amount of work has been dedicated to studying the mechanisms of action of halogenated compounds as gas-phase flame inhibitors. Sheinson et al. [4] developed a methodology to quantify the modes of action of halogenated compounds and showed that brominated compounds exhibit both physical and chemical action, although the chemical action tends to outweigh the physical one. Rosser et al. [5] were the first to propose a mechanism for bromine action as a catalytic flame suppressant. Their mechanism consisted of the for- mation of hydrogen bromide (HBr) followed by two radical trapping http://dx.doi.org/10.1016/j.combustflame.2015.09.031 0010-2180/© 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.