Methods of Collection and Analysis of Acid Gases in Fire Tests

This report documents proven methods of collection and analysis for acid gases in fire tests conducted at the FAA Technical Center. It focuses on methods of collection and analysis requiring trapping hot acid gases at the sampling point and avoiding errors due to sample line losses. The sampling system, collection tubes and procedures are described in this report. Various ion chromatography methods are described which separate and quantify the solution concentration of the anions corresponding to the gases HF, HCl, HBr, HI, HCN, H2S, HIO3, H3PO4, NOx and SOx in complex combustion gas matrices. The ion chromatography methods include the separator columns, suppressor columns, eluents, detectors and autosamplers. The fluoride ion selective electrode method is also evaluated

Accounting for Baseline Drift in the Microscale Combustion Calorimeter

The aircraft industry in partnership with the Federal Aviation Administration (FAA) formed a task group in 2013 to consider using the American Society for Testing and Materials (ASTM) D7309 \u201cStandard Test Method for Determining Flammability Characteristics of Plastics and Other Combustible Solid Materials Using Microscale Combustion Calorimetry\u201d (MCC) as an alternate means of complying with 14 CFR 25 flammability regulations when a combustible constituent of a certified cabin construction is changed due to availability, economics, performance, or environmental concerns. A combustible constituent may be an adhesive, potting compound, film, fiber, resin, coating, binder, paint, etc., formulated with a new flame retardant, pigment, etc., that is used in the construction of a cabin material and can be tested in the MCC at the milligram scale. The use of ASTM D7309 for high precision measurements of aircraft cabin materials for regulatory purposes required a level of accuracy and reproducibility that was beyond the capability of the 2013 version of the ASTM D7309 standard when the FAA-Industry task group was formed. At the time, the calculation of the flammability characteristics did not include a correction for baseline drift- which can be a significant source of error for low flammability aircraft cabin materials. The calculation of the calorimeter signal was revised in 2019 to include the effect of combustion gases, which improved the accuracy of the flammability parameters, and was codified as ASTM D7309-19 and later versions. Correction for baseline drift was complicated by random fluctuations of the MCC signal that precluded the subtraction of a pre-recorded background signal, as is routine in thermal analysis. This report describes an analytic approach to baseline correction that is specific to the MCC and can be used to correct the calorimeter signal for temperature-dependent drift during the test to improve the accuracy and reproducibility of MCC flammability parameters of combustible materials

Flammability properties of PEEK and carbon nanotube composites

Aryl polyetheretherketones (PEEK) show remarkable thermal stability and low flammability, with an onset of decomposition at around 600 °C, and 60% char formation in the cone calorimeter at 60 kW m−2. However, at lower heat fluxes, and in other small-scale flammability tests, it is difficult to obtain consistent results. PEEK polymer has been modified with different types of carbon nanotubes (CNT), leading to modest improvements in the burning behaviour at addition levels between 0.1 and 1%. The characterisation of the composites indicated satisfactory dispersion, modest enhancements in mechanical properties and thermal stability, and reductions of peak heat release rate for the best performing formulations. Significant differences in thermal stability and burning behaviour were observed as a function of the nature of the CNTs, and the loading level within the polymer