基于气泡生长动力学的氢氧化镁阻燃性能分析

为了研究高温下氢氧化镁对沥青阻燃性能的影响,根据氢氧化镁的热解行为和气泡在热沥青中生长过程,基于气泡生长动力学模型,分析了温度及升温速率对氢氧化镁阻燃性能的影响.结果表明:随温度升高,蒸汽泡直径增大,低升温速率使氢氧化镁脱去更多结晶水,阻燃效果更好;气泡界面推进速度出现了迅速减小、维持相对稳定、与氢氧化镁失重率相一致3个阶段,升温速率对这种变化趋势没有明显影响,氢氧化镁的阻燃效率也有类似的变化趋势;液相沥青的径向速率增大较快,说明气泡生长速率增大,当氢氧化镁的失重率较大时,脱去的较多结晶水,吸收的更多热量,释放出较多的水蒸气,阻燃效果更好.可见,温度及升温速率明显影响氢氧化镁对沥青的阻燃性能.

Analysis of flame-retarded performance of magnesium hydroxide based on bubble growth kinetics

To study the flame-retarded performance of magnesium hydroxide in asphalt,the influence of temperature and its rising rate on the flame-retarded performance is analyzed based on pyrolytic behavior of magnesium hydroxide and growing process of bubbles,and the kinetic model of bubble growing is built,too.Study results show that the diameter of steamy bubbles increase with temperature rising.Low temperature rising rate causes more crystal water to decompose from magnesium hydroxide,so the flame-retarded effect is better;Interface velocity of bubbles appears three marked sequential stages,i.e.,rapid decrease,approximate invariability and changes in accordance with the rate of magnesium hydroxide mass loss.The influence of temperature rising rate on the variation tendency of interface velocity is negligible.The tendency of flame-retarded efficiency of magnesium hydroxide is similar with the three stages;The radial velocity of hot asphalt around the bubbles increases rapidly,which shows the growing rate of bubbles increase synchronously.When mass loss rate of magnesium hydroxide is bigger,more crystal water is decomposed from magnesium hydroxide,and more heat is absorbed,and more vapour is released,so the flame-retarded performance of magnesium hydroxide is better.It is obvious that flame-retarded performance of magnesium hydroxide in asphalt is influenced evidently by temperature and its rising rate.