A Colloidal Model to describe the effects of mixing time on filler dispersion in industrial nanocomposites*

The properties of industrial nanocomposites such as tires depend on the degree of filler dispersion under high-shear mixing. Conventionally, the dispersion is quantified through an index based on the reduction in micron-scale agglomerate size observed in micrographs and bulk electrical conductivity measurements. An alternate nano-scale dispersion technique based on x-ray scattering has been proposed.¹ The impact of mixing time on dispersion is investigated taking advantage of the van der Waals equation to describe excluded volume and interaction energy in the dispersion. Herein, an analogy is made between thermally driven true colloidal dispersions and total accumulated strain in nanocomposites. The excluded volume depends only on the filler type and seems insensitive to bound rubber whereas the interaction energy is strongly dependent on viscosity and polymer chemistry. Moreover, the wetting time for nano-scale incorporation of elastomer into filler can be predicted. The description of nano-scale dispersion via a pseudo- second virial coefficient offers the additional possibility of determining the interaction potential that can be used for coarse grained simulations.

¹Y. Jin et al. Polymer 129 (2017) 32