In our previous study we found that addition of proper amount of halocarbons (HC) including chlorocyclohexane (CHC), chlorocyclopentane (CHP), butylchloride (BC), 1,4-dichlorobutane (DCB), and chloroform (C) to the MgCl2 (Ethoxide type)/TiCl4/AlEt3 catalytic system leads to a strong productivity improvement. In this study, the effect of these halocarbons on the properties of resulting polymers was investigated using H-2 as chain transfer agent at optimum HC/Ti molar ratio. The nature of halocarbon compound had a strong effect on polymer properties as well as on development of polymerization activity. Effect of halocarbon promoters on the polymer melt flow index (MFI), melt flow ratio (MFR), particle size distribution (PSD), bulk density, wax amount, crystallinity, and thermal properties of the polymers were studied. Results showed that, in the presence of halocarbons, polyethylenes with higher MFI and bulk density, broader MFR and lower wax amount have been obtained. Also, sieve analysis showed that, in the presence of halocarbons as promoter, polymers had better particle size distribution (PSD). DSC analysis showed that the T-m of PEs prepared with the different promoters were in the region commonly reported for HDPE and was not affected substantially by halocarbons, but, the crystallinity of the polymers has been improved using halocarbon promoters. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 1780-1786, 2010