A mechanism for the polymerization of ethylene and 1-hexene with Cp2HfCl2 was proposed and its kinetic parameters were estimated to quantify ethylene uptake curves and the structure of the polymer made with Cp2HfCl2 when hydrogen concentration, 1-hexene concentration and temperature varied in a solution polymerization. The catalyst follows second order propagation kinetics, and first order catalyst decay kinetics over the range of conditions tested in this study. The Bernoullian model was combined with the Trigger mechanism to describe these copolymerizations, and the parameters for the proposed mechanism were successfully estimated. The models proposed for the conditions in this study describe adequately the polymerization kinetics, polymer M-n, and the average 1 hexene in the polymer made with Cp2HfCl2 for ethylene polymerization with/without hydrogen and ethylene/1-hexene copolymerization. (C) 2019 Elsevier Inc. All rights reserved.