Reaction To Fire Of HIPS/OMMT Composite Under Different Burning Modes

In this thesis, HIPS/OMMT composites (PLS) were prepared by the melt intercalation approach. HIPS and HIPS/OMMT represent the non-charing and charing materials, respectively. The cone calorimeter, LOI and UL-94 methods were used in the study. The analyses showed that the three fire tests correspond to different burning modes. The mechanisms of flame retardancy of HIPS/OMMT composites associated with three methods were discussed. This study examines the burning modes of these fire testing methods as well as the response of PLS material with each mode. Meanwhile, the char residues of PLS composites tested at three different burring modes were analyzed by SEM and TG to investigate the composites and structure of the residues.The cone calorimeter, LOI and UL-94 method are often used to evaluate the flame retardant property of composites. The three burning tests were experimentally analyzed in terms of burning mode based on burning environment, temperature field, flame propagation, heat transfer characteristics. Analysis showed that three different burning experiments represent different burning mode. The characteristics of each mode and reaction to fire of the materials in different burning mode were put forward in the study.The flame retardancy of HIPS/OMMT composites were further investigated. It was demonstrated that OMMT exhibits different flame retardancy in the three different fire tests. By the cone calorimeter method, PLS composites showed excellent flame retardant properties, in terms of peak HRR significantly reduced. When evaluated by traditional fire testing methods (LOI, UL-94), almost no improvement was observed. For example, LOI value for the HIPS/OMMT composites only slightly increased compared to pure HIPS and this is difficult to meet the industry standard. This paper investigated the structure changes of the residues in different stages in different burning modes by SEM. The result shows that from the beginning to the end in the cone calorimeter burning mode, the barrier effect of MMT lamellae was obviously due to forming network char layer structure. For LOI and UL-94 burningon the front surface of samples the barrier effect of MMT was similar to that in the cone, but the gas along the cracks on the side surfaces was easily releasing, which made the role of montmorillonite layer less effective.In addition, effects of the orientations of HIPS/OMMT composites on their burning behavior at the different modes were studied, which shows that the orientation of the MMT layers in the composite affects the burning behavior differently. Also, the effect of NiO on fire performance of HIPS/OMMT was discussed. The cone calorimeter study demonstrated that the flame retardant properties of HIPS/OMMT/NiO composite increased dramatically and the heat release rate was further reduced with the addition of NiO. But when evaluated by traditional fire testing methods (LOI, UL-94), also no improvement was observed. The thermo-gravimetric analysis (TGA) of residues shows that, in the cone calorimeter burning mode, the composites pyrolysised completely, which belongs to the deep cracking burning. In LOI test burning mode and UL-94 test burning mode the pyrolysis was incomplete, which belongs to the surface flame spread burning.