In-situ polymerization of thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) is one of the best methods to obtain nanocomposites with well dispersed nanofillers and superior properties. The effect of nanofillers on reaction is an important factor during in-situ nanocomposite preparation. TPU/CNT nanocomposites were prepared via a sustainable in-situ polymerization of Polycaprolactonediol and 1,4-Phenyldiisocyanate (PPDI) in the presence of multiwall carbon nanotubes. Chemorheological studies conducted at different temperatures indicated that by increasing the temperature, in addition to linear polymerization, branching and crosslinking reactions contribute to viscosity evolution. Empirical and semi-analytical chemoviscosity models were employed to clarify the difference between reaction kinetics of TPU formation in the presence of CNTs. A semi-analytical model developed here, gave more insight into the reaction as well as system structural evolution. Activation energy of viscosity evolution due to polymerization was found to decrease by addition of carbon nanotubes. This acceleration effect is correlated to higher heat conductivity of the nanocomposite as well as CNT effects on the structure evolution in the polymerizing system. (C) 2016 Elsevier Ltd. All rights reserved.