Study of polyethylene blends by differential scanning calorimetry

The melting behaviors of linear and branched polyethylene blends were studied using a Perkin-Elmer DSC-1B differential scanning calorimeter. Three endothermic peaks were occasionally observed in the DSC thermogram on polyethylene blends which had not been subjected to any isothermal annealing. The nature of the third intermediate temperature peak is discussed in relation to the prior cooling rate, the blend composition and the molecular structures of both components. The results appear to indicate that the intermediate peak is associated with the fusion of the hybrid crystallites of linear and branched polyethylenes. These hybrid crystallites seem to be formed on the rapid cooling of lean linear polyethylene blends. Blends containing low molecular weight branched polyethylene seem inclined to form the hybrid crystallites.