升温机制对膨胀型防火涂层隔热性能的影响
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摘要
对水溶性(W型)和溶剂型(S型)这2种膨胀型钢结构防火涂层在ISO 834标准火及3条非标准火升温曲线下的隔热性能进行了试验研究,其中3条非标准火曲线的升温速率及最高温度均低于标准火.试验结束后对不同升温机制下防火涂层的膨胀倍率和膨胀层的泡孔结构进行定性对比分析,并根据隔热性能试验中温度的测量结果计算防火涂层的等效导热系数,用以对不同升温机制下防火涂层的隔热性能进行定量分析.分析结果表明:升温速率影响膨胀-固化阶段气体的逸出率,进而对防火涂层的膨胀倍率产生影响;升温速率不同,发泡剂分解释放气体的时间与熔融态涂层黏滞性的匹配度不同,炭层的泡孔尺寸不同;膨胀倍率越大,泡孔尺寸越小,炭层的隔热性能越好;与标准火下防火涂层的等效导热系数相比,非标准火下防火涂层的等效导热系数均有不同程度的提高,最大差异为65%(W型)和35%(S型);用标准火下膨胀型防火涂层隔热性能的检测结果来指导非标准火(火场温度和升温速率均比标准火低)下防火涂层的设计将导致不安全的结果.
The results of an experimental study were reported on insulation properties of two types of intumescent coating(type-W and type-S) under the ISO 834 fire and three non-standard fire curves which are less severe than the standard fire. After heating test, expansion ratio of intumescent coating and pore structure of chars were measured and compared. Effective thermal conductivities were calculated based on temperature measurements. The results show that expansion ratios can be different when heating speeds up or slows down because more or less gas can be trapped within the coating with varied heating rate. The difference of heating rate affects the matching between timing of gas emission and viscosity of molten polymer, and therefore affects the pore size of intumescent char. The insulative properties of intumescent coating char are better when the expansion ratios are larger and the pore sizes are smaller. The constant effective thermal conductivities derived from non-standard fire tests are 65% and 35% higher than that from standard fire tests for type-W coating and type-S coating respectively, which implies that it is unconservative using standard fire test results to guide design of intumescent coatings under non-standard fire conditions which are less severe than the standard fire.
The results of an experimental study were reported on insulation properties of two types of intumescent coating(type-W and type-S) under the ISO 834 fire and three non-standard fire curves which are less severe than the standard fire. After heating test, expansion ratio of intumescent coating and pore structure of chars were measured and compared. Effective thermal conductivities were calculated based on temperature measurements. The results show that expansion ratios can be different when heating speeds up or slows down because more or less gas can be trapped within the coating with varied heating rate. The difference of heating rate affects the matching between timing of gas emission and viscosity of molten polymer, and therefore affects the pore size of intumescent char. The insulative properties of intumescent coating char are better when the expansion ratios are larger and the pore sizes are smaller. The constant effective thermal conductivities derived from non-standard fire tests are 65% and 35% higher than that from standard fire tests for type-W coating and type-S coating respectively, which implies that it is unconservative using standard fire test results to guide design of intumescent coatings under non-standard fire conditions which are less severe than the standard fire.
引文
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[7] 王玲玲,李国强,徐玉野,等.不同火灾下膨胀型钢结构防火涂层的隔热性能[J].建筑材料学报,2016,19(2):267-279.WANG Lingling,LI Guoqiang,XU Yuye,et al.Insulating properties of intumescent coating for steel element under different fire conditions[J].Journal of Building Materials,2016,19(2):267-279.(in Chinese)
[8] Fire resistance tests—Elements of building construction:ISO 834(1975)[S].
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[10] RUSSELL H W.Principles of heat flow in porous insulators[J].Journal of the American Ceramic Socidety,1935,98:1-5.
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[12] LOEB A L.Thermal conductivity:Ⅷ,A theory of thermal conductivity of porous materials[J].Journal of the American Ceramic Society,1954,37:96-99.
[2] JIMENEZ M,DUQUESNE S,BOURBIGOT S.Characterization of the performance of an intumescent fire protective coating[J].Surface and Coating Technology,2006,201(3-4):979-987.
[3] WANG L L,WANG Y C,LI G Q.Experimental study of hydrothermal aging effects on insulative properties of intumescent coating for steel elements[J].Fire Safety Journal,2013,55(1):168-181.
[4] WANG L L,DONG Y L,ZHANG C,et al.Experimental study of heat transfer in intumescent coatings exposed to non-standard furnace curves[J].Fire Technology,2015,51(3):627-643.
[5] CIRPICI B K,WANG Y C,ROGERS B.Assessment of the thermal conductivity of intumescent coatings in fire[J].Fire Safety Journal,2016,81:74-84.
[6] LI G Q,HAN J,LOU G B,et al.Predicting intumescent coating protected steel temperature in fire using constant thermal conductivity[J].Thin-Walled Structures,2016,98:177-184.
[7] 王玲玲,李国强,徐玉野,等.不同火灾下膨胀型钢结构防火涂层的隔热性能[J].建筑材料学报,2016,19(2):267-279.WANG Lingling,LI Guoqiang,XU Yuye,et al.Insulating properties of intumescent coating for steel element under different fire conditions[J].Journal of Building Materials,2016,19(2):267-279.(in Chinese)
[8] Fire resistance tests—Elements of building construction:ISO 834(1975)[S].
[9] ENV 13381-4(2002) Test methods for determining the contribution to the fire resistance of structural members—Part 4:Applied protection to steel members[S].
[10] RUSSELL H W.Principles of heat flow in porous insulators[J].Journal of the American Ceramic Socidety,1935,98:1-5.
[11] BLASI C D,BRANCA C.Mathematical model for the nonsteady decomposition of intumescent coatings[J].AICHE Journal,2001,47:2359-2370.
[12] LOEB A L.Thermal conductivity:Ⅷ,A theory of thermal conductivity of porous materials[J].Journal of the American Ceramic Society,1954,37:96-99.