Two commercial polyethylene samples, linear high-density polyethylene (HDPE) and branched linear low-density polyethylene with almost the same molecular weight distribution but different contents of short-chain branching (SCB) were melt blended based on the consideration of practical application. Dynamic rheology analysis indicated good compatibility of all the blends with different compositions. Common differential scanning calorimeter (DSC) tests and successive self-nucleation and annealing (SSA) treatment showed several interesting phenomena. First, without consideration of the effect of molecular weight and molecular weight distribution impact, co-crystallization occurred at all ratios even the two components had a considerable difference in SCB distribution. Second, in SSA curves the area of the first two melting peaks, i.e., the amount of the thick lamellas of the two components showed an obvious positive deviation with the increase of HDPE content owing to the crystal perfection improved by the co-crystallization. Essential Work of Fracture tests proved the co-crystallization effects had a positive effect on the improvement of the resistance to crack propagation. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013