不同火灾下膨胀型钢结构防火涂层的隔热性能

基于36个试件在标准火与大空间火下的隔热性能测试,计算膨胀型钢结构防火涂层的等效导热系数,研究升温条件对防火涂层隔热性能的影响规律及机理.结果表明,防火涂层是否反应完整取决于火场的最高温度,升温速率影响膨胀-固化阶段防火涂层的发泡程度;升温历史不同,防火涂层的膨胀倍率和炭化层泡孔结构不同,最终表现为防火涂层隔热性能的差异.防火涂层在标准火下的隔热性能优于大空间火下的隔热性能,两者的等效导热系数代表值λr最大差异为65%.升温速率越快,火场最高温度越高,防火涂层的等效导热系数值越低,隔热性能越好,因此,用标准火下防火涂层隔热性能的检测结果来指导大空间火下防火涂层的设计是不安全的.大空间火下防火涂层等效导热系数随升温条件变化的程度还要受涂层厚度的影响,随涂层厚度增加,不同工况下的防火涂层等效导热系数差异程度减小.

Insulating Properties of Intumescent Coating for Steel Element under Different Fire Conditions

36 specimens were tested under standard fire and large space fires. Effective thermal conductivities of intumescent coatings were calculated based on test measurements. The effect of the fire condition on thermal insulating properties of the intumescent coating was investigated, and the mechanism of difference in insulating properties was discussed. The results show that whether the reaction process is completed is dependent on the maximum temperature of fire, and that the foaming degree of coating was affected by the heating rate. Therefore, different expansion ratios and pore structures were obtained under varied fire conditions with the result that the insulating properties changed. The effective thermal conductivities of intumescent coatings under standard fire are much lower than that of large space fires, and the maximum difference is up to 65%. Increase in the temperature and the heating rate results in better insulating properties of the coating. It is unsafe to use the standard test result guides design of intumescent coating under large space fire. The variance degree of insulating properties for intumescent coating under large space fires was affected by coating thickness. The difference was smaller when the coating was thicker.