Using The Mooney Viscometer

Abstract The increased use of the Mooney viscometer in America for checking the plasticity of different batches of synthetic rubber has led to a wider appreciation of the care which is necessary for accurate operation of this apparatus. A recent article dealt fairly fully with most of the factors affecting results obtained with the Mooney viscometer. Some results obtained on the instrument at Blackley are extremely interesting and publication may help other users to avoid the trap of using Vistanex for calibration purposes. Vistanex is a stable material chemically, which is essential for a standard material, but other factors overcome this advantage and preclude its use. The mechanical method of calibrating the machine checks the spring at readings 0 and 100 and as long as the spring is not taken beyond its elastic limit there is no point in checking intermediate values. Vistanex gives a reading of 50 when tested at 100° C in the standard manner. It has been assumed that if a reading of 50 is obtained with Vistanex, the instrument must be working correctly. This view is wrong.