Dissipative Particle Dynamics Models of Orientation of Weakly-Interacting Anisometric Silicate Particles in Polymer Melts under Shear Flow: Comparison with the Standard Orientation Models

Dissipative particle dynamics (DPD) models of orientation of weakly-interacting silicate particles in a polymer matrix are presented. To examine the DPD models, the evolution of orientation under shear flow is compared with the predictions of the standard orientation models, namely, the Folgar-Tucker (FT) and the strain reduction factor (SRF) models. While the orientation patterns are the same in all models, the slow orientation kinetics observed in previous experiments is only predicted in the DPD and SRF models. Since the coefficients of the SRF model are in good agreement with the experiments, the good tally between the DPD and SRF models supports the capability of DPD to successfully simulate the orientation process. The orientation in a large cell constructed from unit cells with various averaged initial orientation angles is evaluated from evolutions in the unit cells based on the affine deformation assumption. The good agreement between such calculations and SRF model predictions supports that the affine deformation assumption in the large cell is reasonable. It is argued that the nonaffine deformation originated from the particle-based nature of DPD models at the lower scale could be combined with the affine deformation at the upper scale to yield appropriate estimations of the orientation state.