Mooney viscometer

[1][3][4] 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.

The conversion of the torque into viscosity units is made by means of a calibrated flat spring anchored to the rotating disc shaft.

The chamber is electrically heated and the temperature is kept constant within 0.5 degree C. The rubber compound, including the vulcanizing system, is shaped on the mill as 6–8 mm thick sheets.

The following values are indicated on the obtained curve: Optimum vulcanization time at the experimental temperature employed (top), which can be calculated with the relationship: where tMV is the time interval, measured from rotor start until Mooney viscosity reaches the MV value.

Going beyond the plateau time leads to either reversion in natural rubber, or overcure in synthetic elastomers.