Carbon black as a self-diagnosing probe to trace polymer dynamics in highly filled compositions

A new technique for in situ studies on polymer dynamics in highly filled compositions was developed using carbon black (CB) as a self-diagnosing probe. It is based on the fact that CB particles dispersed in the polymer matrix are easy to aggregate and gradually form three-dimensional networks. Real-time monitoring of the dynamic process of the interparticle network formation was realized by tracing the time dependence of electrical resistivity during isothermal treatments. We investigated the influence of time, temperature, concentration, and the molecular weight of the polymer matrix on the dynamic percolation behavior and concluded that the percolation time when the electrical resistivity starts to decrease drastically is directly related to the zero-shear-rate viscosity of the polymer matrix. We also estimated the terminal relaxation time of polymer matrices from the dynamic percolation curves so as to eliminate the effect of CB concentrations. It is expected that the dynamic percolation measurements may provide an incisive method to study the influence of particle-polymer interactions on the relaxation and viscoelastic properties of a polymer matrix.