Fluids can be categorized as Newtonian and non-Newtonian. The viscosity of the Newtonian fluids remains constant at all shear rates at a constant temperature and pressure. But, for a non-Newtonian fluid, the viscosity varies with the shear rate and time. Thixotropic epoxies are non-Newtonian fluids which are gel-like at rest, but tend to flow when agitated or stressed. The particles of this type of product are held together by weak forces at low shear rates, whereas at high shear rates the particles tend to separate.
The viscosity for thixotropic materials can be measured at different shear rates using a viscometer. Using this data, the viscosity associated with a particular spindle shape and RPM can be obtained.
Master Bond offers many epoxies which exhibit thixotropy. These epoxies are used widely as adhesives and sealants in applications where non-drip and high viscosity characteristics are desirable. Both one component heat curing systems and two component room temperature curing systems are available under the category of thixotropic adhesives. These adhesives also offer other properties like excellent electrical insulation properties, high thermal conductivity and resistance to high temperatures.