Dynamic Shear Rheology and Structure Kinetics Modeling of a Thixotropic Carbon Black Suspension

Abstract The rheological characterization of a model, nearly ideal thixotropic carbon black suspension first proposed by Dullaert and Mewis (JNNFM 139: 21-30, 2006) is extended to include large amplitude oscillatory shear (LAOS) flow, shear flow reversal, unidirectional LAOS flow (UD-LAOS). We show how this broader data set is useful for validating and improving constitutive models of thixotropy. We apply this new data to further test a recently developed structure-kinetics model, the Modified Delaware Thixotropy Model, (Armstrong et al. J Rheol. 60: 433-450, 2016) as well as to better understand the microstructural basis and validity of strain rate superposition methods proposed with the framework of soft glassy rheology (SGR) modeling. This comparison identifies the limitations of models based on a scalar description of microstructure, which cannot fully capture the reversal of flow directionality inherent in LAOS flow. Further, we use the model to identify a possible microstructural justification for the hypothesized technique of strain rate superposition in the SGR model.