In this work, the effects of three types of cocatalyst having different alkyl groups, such as triethylaluminium (TEA), triisobutylaluminum (TiBA), and trioctylaluminium (TnOA), and their concentrations on the catalytic activity and polymer properties were investigated for the Ziegler–Natta catalyst containing alkoxide species. The drastic escalation of catalytic activity was observed when the ratio of Al/Ti was increased only for TEA because of its good diffusivity as proven by the electron spin resonance technique. Moreover, it was found that the characteristic of the alkyl group in cocatalyst affected on the chain transfer ability. The chain transfer ability of TnOA was found to be equal to the TiBA in spite of its concentration was higher. By the way, the cocatalyst types and their concentrations did not affect on the variety of active sites as seen in molecular weight distribution of polymer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40884.

Summary Semi‐batch propylene polymerizations were performed in slurry and gas phase using a supported Ziegler‐Natta catalyst. The obtained instantaneous reaction rates were fitted with a kinetic model, and the influence of bulk temperature and reaction phase on kinetic parameters was studied. The estimated propagation constant increased with increasing reaction temperature up to 90 °C in slurry phase polymerizations, but reached a maximum at 60 °C when propylene was polymerized in the gas phase. Gas phase stopped flow reactions were done at 60 and 70 °C to investigate the strong influence of temperature during the initial instants of reaction and to evidence thermal degradation at particle level. These results and those from autoclave reactor were well consistent and could explain the effects of temperature.