Mooney torque peak

There have been a number of developments of the Mooney test. The generally useful and accepted one has been the Delta Mooney test, which has achieved the status of an ASTM test, and is well recognized within the industry. Other techniques which have been reported are Mooney recoil, initial Mooney torque peak (PMT), and variable-speed Mooney tests. 

In the rubber industry a double parallel plate device, the Mooney Wscometer (ASTM D1646) is used to measure viscosity, Data is normally reported in Mooney units fi om 0 to 100, but these can be translated to torque and analyzed by eq. 5.5.8 (Naka-jima and Collins, 1974). Another rubber indexer is the oscillating disk curometer, which is typically a bicone oscillating at 3 Hz in a disk-shaped cavity (ASTM D2704). Peak torque is reported on a scale of 0-100, but if the amplitude is known, this can be translated to G. However, at high G levels and the usual operating conditions wall slip can occur. 

The standard procedure [14] requires 1 minute of preheating before the rotation is started. Because the temperature is set at for example, 100 °C, the sample is not even in temperature equilibrium. The procedure is obviously a compromise for obtaining the data quickly. The rotational speed being 2 rpm, most of the rubber at 100 °C shows stress-over-shoot (see section 4.3) [6]. The torque value is recorded after 4 minutes of rotation and expressed as the Mooney unit. At 4 minutes, the torque is usually past the peak and in the relaxation part of the curve but not in the steady state. This is shown in Figure 6.1, for somewhat exaggerated examples, which gave the same Mooney index but vary in viscoelastic behaviour. 

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