In the present publication, a method to identify and distinguish between different types of low-density polyethylene based on thermal fractionation and FTIR analysis is described. It was shown that during thermal fractionation four to seven endothermic peaks are obtained as opposed to one or two peaks obtained during regular differential scanning calorimetric analysis. The ratio between band heights at 1368 and 1376 cm(-1) was found to represent the length of the side chain (branch).