Study On The Influence Of Environment Pressure On Pyrolysis,Ignition Performance And CO Release Of Non-charring Black ABS

Non-charring polymers is increasingly used in the modern society,however,they can pyrolysize under the external heat flux and start to burn when the certain environment is achieved,with the toxic gases escaping.These gases are harmful to the health and wealth of people.So far,there are some researchers contribute to the study of pyrolysis and combustion process of non-charring polymers under external heat flux.But in the high-altitude areas or some special low-pressure and poor-oxygen areas,the fire behavior is significantly different from that in the natural environment for the change of fire scenario,and so far,the study on fire behavior of the polymers under different pressures is still scarce.Meanwhile,the study on polymers' fire behaviors under poor-oxygen conditions is indispensable for the existence of backdraft in enclosed compartment,but still the study on it is also scarce.In this paper,a series of experimental and theoretical researches are conducted to investigate the pyrolysis behavior,auto-ignition performance and toxic gas(release of CO)of non-charring black acrylonitrile-butadiene-styrene(ABS)under different pressures.The surface absorption one dimension pyrolysis model is developed based on the experiments.The toxicity of CO is assessed by FED disability model and the relationship of CO toxicity,CO concentration and exposure time is discussed.At first,the experiments are conducted to investigate the influence of external heat flux and pressure on the pyrolysis behavior of ABS.Char residue,top-surface and bottom-surface temperature and mass loss rate of sample are observed and analyzed.The total pyrolysis time under different cases is fitted with pressure.The results show that pressure can affect the heat convective coefficient and the escaping rate of pyrolysis gases,and affect the Char residue,top-surface and bottom-surface temperature and mass loss rate further.The effect is more significant under low heat flux.As the pressure goes up,the bubbles in char residue get bigger,the temperature and the mass loss rate get down.For the change of pyrolysis rate,those pyrolysis parameters have different respond toward pressure under different external heat fluxes.And the total pyrolysis time is proportional to pressure.Based on the energy conservation,the surface absorption one dimension pyrolysis model is developed to predict the top-surface and bottom-surface temperature and mass loss rate.The theoretical results are compared with the experimental results,and the application range is also discussed.The comparisons show that there is some discrepancy between the two results for some reasons:the discrepancy of thermo-physical properties,the absorption way and the melting of sample.But in general,the theoretical results fit well with the experimental results.The prediction under high heat flux is better,and the prediction under low pressure is better.Finally,the experiments are conducted to investigate the influence of external heat flux and pressure on the auto-ignition and the release of toxic gases of ABS.Ignition delay time and critical ignition temperature are observed and analyzed.The escaping behavior of CO is also analyzed.The FED disability model is used to assess the toxicity of CO,uncovering the relationship of CO toxicity,CO concentration and exposure time.The results show that ignition delay time and critical ignition temperature of sample respond differently to the pressure under different external heat flux.Under 30?50kW/m2 heat flux,the CO concentration is inversely proportional to pressure.