Materials with viscosities greater than 10 Pa-s (10,000 centipoise) are considered to as viscous materials - examples include polymers, putties, chewing gum, solid propellant. These materials exhibit characteristics such as flow resistance, Non-Newtonian behavior. Therefore, flow currents do not get formed while mixing of viscous materials. Mixing in viscous materials is effected by mechanical action resulting in forced shear and elongation flow of the matrix. Mixing of viscous material necessitates dispersive mixing, distributive mixing and convective mixing mechanisms to occur in a systema.

Sigma blade mixers are the most commonly used mixers in the family of double arm mixers.

The sigma mixer extruder contains a set of kneading blades and one or two extrusion screws that are contra-rotating.

The double planetary mixer consists of a mixing vessel with two beaters that rotate on their own axes, while they orbit the vessel on a common axis.

The planetary mixer is so called because inside the mixer bowl the mixing agitator (commonly known as the beater) rotates in a planetary movement.

Dual and Tri-shaft mixers are used for high viscosity materials, with different types of mixing elements, each provided for a specific function.

As the name suggests, contra-rotating mixers consist of agitators rotating in opposite direction.