泡沫灭火剂热老化机理研究

Thermal aging mechanisms of foam fire extinguishing agents

水成膜泡沫灭火剂在长期储存过程中存在由于老化而导致性能下降的问题。为了研究泡沫灭火剂的老化降解机理,分别在60℃和90℃下对灭火剂进行加速热老化192 h,研究了灭火剂在老化前后的性能变化;采用液相色谱-质谱联用技术(LC-MS),通过灭火剂在老化前后的离子流变化分析了碳氢表面活性剂的降解情况;采用核磁共振氢谱法(~1H NMR)定量分析了不同pH环境对碳氢表面活性剂稳定性的影响。结果表明:在60℃和90℃下加速热老化192 h后,泡沫灭火剂的发泡倍率明显下降,pH值显著升高,表面张力未发生明显变化;在90℃下热老化192 h后,烷基链长度在C以下的碳氢表面活性剂发生了明显降解,烷基链长度为C和C的碳氢表面活性剂相对稳定;在90℃下热老化192 h后,糖苷类表面活性剂在酸性和碱性环境下的降解率大于中性环境,甜菜碱类表面活性剂在碱性环境下的降解率大于酸性和中性环境,因此在实际应用时应避免添加导致体系pH大幅升高的组分。

Aqueous film-forming foam fire extinguishing agents suffer from performance degradation due to aging during long-term storage.In order to study the aging degradation mechanism of foam fire extinguishing agents,the fire extinguishing agents were subjected to accelerated thermal aging at 60℃and 90℃for 192 h,and the performances of the fire extinguishing agent before and after aging were compared.The degradation of hydrocarbon surfactants was analyzed by liquid chromatography-mass spectrometry(LC-MS)by monitoring the change in ion flow of the fire extinguishing agent before and after aging.The effects of different pH on the stability of hydrocarbon surfactants were quantitatively analyzed by proton nuclear magnetic resonance spectroscopy(~1H NMR).The results showed that after accelerated thermal aging at 60℃and 90℃for 192 h,the foaming ratio of the extinguishing agent decreased significantly,the pH value increased significantly,whilst the surface tension did not change significantly.After thermal aging at 90℃for 192 h,hydrocarbon surfactants with alkyl chain lengths below Cwere degraded significantly,whilst hydrocarbon surfactants with alkyl chain lengths of Cand Cwere relatively stable.After thermal aging at 90℃for 192 h,the degradation rates of glycoside surfactants in acidic and alkaline environments were higher than that at neutral pH.The degradation rate of betaine surfactants in an alkaline environment was higher than in acidic and neutral environments.In terms of practical application,the addition of components leading to a significant increase in pH should be avoided.