ASTM D 1646: Standard Test Method for Rubber - Viscosity, Stress Relaxation, and Pre-Vulcanization Characteristics (Mooney Viscometer)
The Mooney Viscosity is the most widely used processability criterion in the rubber industry. The working principle of the Mooney viscometer consists in the measurement of the torque necessary to rotate a disc in a cylindrical chamber filled with the rubber compound to be vulcanized. A number proportional with the value of this torque is taken as viscosity index (Mooney viscosity) and is reported in arbitrary Mooney units.
The rubber compound is introduced under pressure into the test chamber, made up of two halves. Inside the test chamber a disc is rotated by means of a motor. To avoid rubber slippage during the determination, both the chamber walls and the rotor surface are striated.
ASTM D1646 - Section 4.Summary of Test Methods: Part A-Viscosity, Part B-Stress Relaxation and Part C-Pre-Vulcanization Characteristics
All three testing methods use the same Mooney Viscometer unit but measures different torque measurements at different times of the test sequence. Scorch testing is also available on the software as well.
Typical stress relaxation test torque curce from a Mooney Viscosity test