The dynamic rheological behavior of low-density polyethylene (LDPE)/ultra-high-molecular-weight polyethylene (UHMWPE) blends and linear low-density polyethylene (LLDPE)/UHMWPE blends was measured in a parallel-plate rheometer at 180, 190, and 200 degrees C. Analysis of the logadditivity rule, ColeCole plots, Han curves, and Van Gurp curves of the LDPE/UHMWPE blends indicated that the blends were miscible in the melt. In contrast, the rheological properties of LLDPE/UHMWPE showed that the miscibility of the blends was decided by the composition of LLDPE. The differential scanning calorimetry results and scanning electron microscopy photos of the LLDPE/UHMWPE blends were consistent with the rheological properties, whereas with regard to the thermal and morphological properties of LDPE/UHMWPE blends, the results reveal three endothermic peaks and phase separation, which indicated a liquidsolid phase separation in the LDPE/UHMWPE blends. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013