Post fire materials identification by micro-Raman spectroscopy and principal components analysis

The chemical and physical characteristics of thermally damaged polymers, found in fire debris are studied using micro-Raman spectroscopy for identifying original materials in a fire compartment. Six polymeric materials commonly found in households were selected for the initial study. They are, polypropylene (DVD case), polystyrene foam (plates), polyurethane (sofa foam), polyester (PET curtains), Ethylene vinylacetate (EVA shower curtains) and nylon (stockings). Raman shifts were obtained for each material prior to them, being burnt as the baseline for determining the loss of Raman bands due to a material modification by the fire. Each material was then burnt, and the subsequent Raman spectra collected. The average Raman spectra for each material were subjected to principal component analysis, which showed that after thermal decomposition, Raman spectroscopy could be used to identify and differentiate materials found in burnt debris. Raman spectra for each material were distinguishable in the sample group and could then be used for identification of the material in their post fire state.