Stress-Optical Relationship for Particle Dispersion Systems

Simultaneous measurements of complex modulus and complex strain-optical (birefringence) coefficient were performed for silica particle suspensions in order to clarify the stress-optical relationship. The dynamic modulus was found to be described with three Maxwell models. The strain-optical coefficient changed its sign form positive to negative with increasing frequency, suggesting the coefficient was composed of two relaxation modes. The relationship between stress and birefringence were found to be described with the modified stress-optical rule, composed of two relaxation modes. The fast mode having negative birefringence was assigned to the anisotropic distribution of particles due to deformation. The slow mode having positive birefringence was tentatively assigned to the aggregation of particles. Although the examined particle dispersion system was not ideal it was strongly suggested that the stress-optical rule would hold valid for the ideal hard particle dispersion systems.