Kinetic Features of the Crosslinking Process for Compositions Based on Butyl Rubber and Dispersed Fillers

The kinetics of formation of a three-dimensional structure in compositions based on butyl rubber and silicon-containing hyperbranched polymethylsilsesquioxanes and MQ copolymers is studied in comparison with compositions containing common dispersed phases: carbon black and silica. Features of the chemical structure of the synthesized organosilicon polymers make it possible to treat the morphology of their elementary particles as core–shell. The role of an inorganic “core” is played by silica structures, whereas methyl shells should ensure compatibility with the carbochain matrix of the rubber. Quinol ether is used as an agent of crosslinking via double bonds of the isoprene part of the rubber. The crosslinking process is carried out in the mode of continuous heating of compositions with registration of thermal effects by differential scanning calorimetry and dynamic moduli by oscillatory rheometry. The apparent activation energies of the process of chemical crosslinking under nonisothermal conditions are calculated in terms of various models. It is shown that the apparent activation energy of crosslinking is lower for filled systems. This indicates that rubber macromolecules are partially uninvolved in chemical crosslinking as a result of adsorption and loss of relaxation mobility. The adsorption activity of fillers is estimated from a difference in the activation energies of the initial rubber and filled compositions; this parameter is the lowest for polymethylsilsesquioxanes.