A study on nitrile rubber/polyvinyl chloride blend vulcanization kinetics with different fillers by using single isothermal rheograph

An attempt has been made to establish a reasonably accurate microkinetics model for accelerated sulfur vulcanization of commonly used acrylonitrile rubber/polyvinyl chloride (NBR/PVC 70/30) blend (NVC73) from a single, isothermal rheograph data of torque versus time. The effect of three different types of fillers, such as pre-exfoliated organically modified montmorillonite (OMMT) clay, graphite (GRT) powder, and high abrasion furnace (HAF) carbon black (CB), were studied. The kinetics study was done with six solid-state reaction kinetics models. Among these, Sestak-Berggren (SB) equation was found to be the best model for the present compositions. The SB kinetic rate expressions were evolved after several iterations using empirical values of autocatalytic and non-autocatalytic orders of ‘m’ and ‘n’, respectively. The gum vulcanizate and OMMT clay-loaded compositions were found to have comparable conversion function f(α) and almost identical reaction rate constants at 150°C, under isothermal conditions. In comparison, HAF CB and GRT rate expressions differed from clay-loaded compositions. The validity of the reaction rate equations obtained was confirmed by comparison of plots for experimental and derived conversions with time.