Rheological behavior and microstructural mechanisms in non-colloidal suspensions across newtonian and non-newtonian matrices: microscopic and macroscopic relationship

Abstract

Understanding how microscopic particle interactions translate into macroscopic rheological behavior remains a central challenge in non-colloidal suspensions. This work proposes a unified experimental approach to investigate how particle properties—size, shape, surface roughness, and concentration—interact with the microstructure of different fluid matrices. Model suspensions were prepared using xanthan gum, Carbopol, and Laponite, with identical particle systems to decouple particle-induced effects from matrix-controlled mechanisms. The results show that particle concentration governs transitions between rheological regimes, affecting viscosity, viscoelastic properties, and flow behavior. However, the underlying physical mechanisms strongly depend on the matrix. In pseudoplastic systems, particle addition promotes polymer-mediated coupling; in viscoplastic gels, particles can either reinforce or disrupt the network; and in thixotropic systems, they influence structural evolution and aging kinetics. Overall, smaller particles enhance particle–matrix interactions, increasing elastic contributions, while higher concentrations promote structural connectivity and yield stress behavior. No universal rheological model describes all systems, as stress transmission is governed by the intrinsic microstructure of the continuous phase. This work establishes a matrix-dependent framework linking microstructure to macroscopic rheological response in non-colloidal suspensions.