Rheology and Viscosity
Rheology is the study of flow and deformation of materials under applied forces which is routinely measured using a rheometer. The measurement of rheological properties is applicable to all materials – from fluids such as dilute solutions of polymers and surfactants through to concentrated protein formulations, to semi-solids such as pastes and creams, to molten or solid polymers as well as asphalt. Rheological properties can be measured from bulk sample deformation using a mechanical rheometer, or on a micro-scale by using a microcapillary viscometer or an optical technique such as Microrheology.
Rotational rheometry is a powerful technique for the measurement of complex shear rheology across all material types – sensitive enough to measure the viscosity of dilute polymer solutions, and yet robust enough to measure the viscoelasticity of high modulus polymers or composites. Rotational rheometry is ideal for discerning structural and compositional changes of materials, which can be critical controlling factors in flow and deformation properties, and ultimately product stability and performance.
Capillary rheometry has its origins in polymer melt processing, but is also directly relevant to many other material processes such as high speed coating and printing applications. Based on controlled extrusion of a test material, capillary rheometry enables material flow and deformation properties to be characterized under conditions of high force (or pressure), high shear rate and at elevated temperature.