HIPS/OMMT纳米复合材料的燃烧性能与其残余物炭层结构特征研究

CHARACTERISTICS OF FIRE RESIDUES OF HIPS/OMMT NANOCOMPOSITES FORMED DURING CONE CALORIMETER TESTS

采用SEM、XRD、TGA等分析方法对高抗冲聚苯乙烯/有机蒙脱土(HIPS/OMMT)纳米复合材料在燃烧过程中形成的炭渣残余物结构特征进行了研究,包括炭层断面形态,片层结构及炭渣热稳定性等.结果表明复合材料在热释放速率峰值之后,形成了具有阻燃作用的炭层结构,其特征是在炭层表面形成了一层比较薄但密实的皮层,皮层之下是较厚的一层蜂窝层,这种"皮-窝"结构赋予炭层良好的阻隔热的作用,减缓了热分解过程.XRD分析还表明原有插层结构经过燃烧已破坏,在皮-窝炭层中都已消失,结合SEM观察结果,蒙脱土片层多以剥离的单片层无规分布,皮层和窝层中聚合物已基本烧蚀,只剩下片状的蒙脱土聚集在一起形成了一种纳米尺寸的网状结构并包含了一定量的分解温度很高的碳质物质,不仅形成了稳定的保护层,而且碳质物质的生成也降低了材料分解挥发速率.窝层含有大量尺寸较大的空穴结构,隔气效果不如皮层,但显著地增大了炭层的体积,整体上能起到较大的隔热作用.二者共同构筑的皮-窝炭层结构在复合材料的燃烧过程中起到了阻燃的作用.

SEM,XRD and TGA were used to study the characteristics of fire residues of high-impact polystyrene/arganic montmorillonite（HIPS/OMMT） nanocomposites formed during cone calorimeter tests,including residue cross-section morphology,montmorillonite platelet distribution,thermal stability and pyrolysis characteristics of the residues.The results show that the residue formed after the peak heat release rate（HRR） is composed of a thin and dense skin layer at the surface of the residue and a cellular layer beneath the skin layer.It is the skin-cellular layer structure that makes the residue layer perform a good insulation effect.XRD data and SEM observations show that the intercalated structure in the original nanocomposite is not found in the skin and cellular layers,while randomly distributed montmorillonite platelets aggregate and form a network-like structure.TGA analysis shows that both the skin layer and the cellular layer formed in the half burnt samples are mainly composed of montmorillonite with a certain amount of carbonaceous char,which not only form a protective layer,but also reduce the volatile due to the formation of carbonaceous components.Although the cellular layer is not as good as that of the skin layer in terms of permeability,the cellular layer considerably augments the thickness of the residue.It is the good combination of the skin and cellular layers that reduces the flammability of the nanocomposites.