Rotational rheometers are predominantly used to investigate the rheological properties at gaps of 10 times the length scale of microstructural feature in the material system. In general, high shear and narrow gap rheology assist many of industrial processes and a wide range of applications in product designing in industries like food, building materials and coatings. Thin gap rheological measurements involve the exploration of rheological properties at gaps where the material system is confined to very thin gaps, so that response of the confined microstructure can be examined as well as higher strain rates can be achieved.

In the present study, the instrumental artefacts associated with thin gap rheological experiments with parallel plate geometry is addressed and compared in two different traditional rheometers. Since many of the industrial coating processes use particle-filled suspension for the process as well as product design, non-Brownian suspension in a polymer matrix is studied, and the effect of thin gap on the rheological behaviour of suspension in the polymeric solution is investigated. At the thin gap closer to the size of underlying microstructure in low shear rate regime, ‘shear jamming’ is observed in steady shear experiments. The relation between relative viscosity with different concentration of hollow glass microspheres in the polymer medium is also correlated. The overall goal of this work is to understand the effect of the narrow gap on the particle interactions in the polymeric matrix, and the influence on the deformation behaviour at different confinements.