密度对聚氨酯软泡收缩及燃烧行为的影响

采用锥形量热仪研究不同密度聚氨酯软泡(FPUF)的燃烧行为,并根据摄像、体视显微镜所观察的样品形体及泡孔结构的变化来研究火灾条件下FPUF的收缩特性。研究结果表明,收缩是表层泡孔受热发生热解生成焦油所致的泡孔塌缩现象,焦油层下方泡孔结构基本没有变化;FPUF密度越大着火前的收缩速率越小,同一时刻表层泡孔热解生成的焦油层越薄。FPUF的着火燃烧可分为受热收缩、燃烧收缩和池火燃烧三个阶段。中高密度样品HRR曲线先出现平台后出现峰值,分别对应于燃烧收缩和池火阶段,且密度越大HRR曲线的平台越低、峰值越高,燃烧收缩阶段的FIGRA越小,而池火燃烧阶段的FIGRA越大。着火前的快速收缩导致低密度样品的HRR曲线不出现平台只呈现单峰。

Influences of density on the shrinkage and combustion behaviors of flexible polyurethane foam

In order to explore the influences of density on the shrinkage and the combustion behaviors of flexible polyurethane foam (FPUF) in simulated fire conditions, the heat release rate (HRR) data of FPUF specimens with different densities were measured by a cone calorimeter. The variations of specimen shape and cell structure were observed by using a camera and a microscope. The results showed that the shrinking originated from the pyrolysis of FPUF, which produced the tar and resulted in the collapse of surface cell exposed to the heat source. The cell structure below the tar hardly changed. As the density of FPUF increased, both the shrinkage rate before ignition and the tar thickness at 10 s decreased. The combustion of PFUF could be divided into three stages: shrinking before ignition, shrinking after ignition and pool fire. For medium and high density FPUF specimens the HRR curve had a platform followed by a peak and the fire growth index (FIGRA) curve (denoting the HRR divided by the time) had two peaks. As the density increased, the HRR platform decreased and the HRR peak increased, and the first FIGRA peak decreased and the second FIGRA peak increased. Due to significant shrinking before ignition the FPUF specimen of 15 kg/m3 had only one HRR peak and one FIGRA peak.