Polymer Toxicity Characterization
WHA has developed a test system to help characterize the toxicity of combustion products generated when polymers burn in oxygen. This test system and methodology was designed to support the toxicity risk assessments in standards such as ISO 15001, CGA 4.10, and EIGA Doc 73/08.
Combustion products are produced by igniting a polymer sample (100 mg) using WHA's adiabatic compression test system. The test sample holder includes an orifice directly downstream of the sample and is attached to the adiabatic compression test system downstream of the fast-acting valve (Fig. 1). When the sample ignites and is consumed, the combustion products flow into the downstream volume (Fig. 2) and are captured in the gas sampling cylinder.
Figure 1 - WHA's Combustion Product Capturing Test System
Figure 2 - WHA's Polymer Sample Holder
The captured gases are analyzed using Draeger tubes for the acid gases (Fig. 3) and other gases are sent to the NASA White Sands Test Facility for further analysis by gas chromatography, mass spectrometry and ion chromatography.
Figure 3 - WHA's Combustion Product Analysis System
The analysis of the combustion products identifies the combustion product species and also determines the concentrations (i.e., ppm) in the oxygen gas. These results can then be applied to any oxygen breathing system, such as the one shown in Figure 4, to determine the potential dosage received by the breathing user, for analysis by a toxicologist. The toxicological analysis uses LC50 data from sources such as ISO 10298, but most of this data represents lethal concentrations for durations of one hour or even longer. Initial WHA testing has shown that for medical oxygen systems, such as the one shown in Figure 4, the duration of exposure (i.e., dosage) occurs within one minute. Therefore, the analysis needs to extrapolate data to shorter durations. The goal of the toxicological analysis is to provide a toxicity risk which can then be weighed against the risk of ignition and fire.
Figure 4 - Example of an Oxygen Breathing System