Carbon Black Network Breakdown

Carbon black network breakdown            

Omer Gozen, Mindaugas Rackaitis and Christopher Robertson

Bridgestone Americas Center for Research and Technology, Akron, OH, USA

Understanding the extent of mechanical deformation in filler-based polymeric systems has been of great interest in performance-related tire and non-tire applications. In this study, we have focused our efforts on investigating the network breakdown of reinforcing carbon black by itself and in cured polybutadiene rubber through conductive rheological measurements in a strain-controlled ARES rheometer at different strain levels. According to the analysis of electrical current fluctuations, our results have shown a profound effect that carbon black network exhibits Payne effect without the surrounding polymer matrix. At lower strain levels (0.1 to 0.5%) the current that runs through the carbon black cake displays almost a sinusoidal behavior. Upon an increase in the strain level, the amplitude of the current goes over a maximum similarly as it is observed in a carbon-black-filled polybutadiene rubber. This behavior can be correlated to the breakdown of the carbon black network. Fast Fourier Transform (FTT) analysis shows appearance of multiple frequencies in the current signal that suggests the existence of finite size pieces of network that are broken from the sample and are responsible for higher harmonics. This method can be a useful way to reveal the microscopic behavior of filler particles and particle networks in filled rubber or other similar systems.