Mooney cavity

In the Mooney shearing disk viscometer, a serrated disk is rotated ia a sample fixed ia a pressuri2ed cavity. The instmment was developed for mbber and other elastomeric materials and is a standard quaUty control iastmment ia the mbber iadustry (ASTM D1646). It is used to measure high viscosities givea ia arbitrary Mooaey units, but usually ca 7.5 x 10 mPa-s atlow(ca 1.5 ) shear rates. 

Melvin Mooney devised an instrument to measure the stiffness of uncured compounds, also known as the compound s viscosity. The unit of measurement is expressed in Mooney units. Figure 28.1 shows an instrument set up for measuring viscosity, the Mooney viscometer, in which a knurled knob (rotor) rotates (at 2 revolutions per minute) in a closed heated cavity filled with rubber [2]. 

Over the twentieth century, the mbber industry has developed special rheometers, essentially factory floor instmments either for checking process regularity or for quality control purposes, for instance, the well-known Mooney rheometer (1931), the oscillating disk rheometer (1962), and the rotorless rheometer (1976). All those instmments basically perform simple drag flow measurements but they share a common feature During the test, the sample is maintained in a closed cavity, under pressure, a practice intuitively considered essential for avoiding any wall slip effects. Indeed it has... 

Choosing the correct flow period is a very important aspect in the forming and shaping process. Mooney cure curves give good data on the flow period. The flow period also depends on the flow distances in the cavities of the mould and the viscosity of the rubber stock and the repeat pressure application cycles, called "bumping" cycles on the shop floor. 

A number of plastimeters of this type have been used for rubbers, often for research purposes, but one instrument, the Mooney viscometer, gained virtually universal acceptance and has been extensively used for routine quality control purposes for several decades. The principle of the Mooney is shown in Figure 6.4 together with several other possible geometries for a rotational instrument. The rotor turns at a constant rate inside a closed cavity containing the test piece so that a shearing action takes place between the flat surfaces of the rotor and the walls of the chamber. The torque required to rotate the rotor is monitored by a suitable transducer. 

In the oscillating disc a bi-conical disc is anbedded in the rubber in a closed cavity, such as with the Mooney. The disc is oscillated through constant angular displacement and the torque monitored. 

Scorch resistance is usually measured by the time at a given temperature required for the onset of crosslink formation as indicated by an abrupt increase in viscosity. The Mooney viscometer is usually used [4]. During this test, fully mixed but unvulcanized rubber is contained in a heated cavity. Imbedded in the rubber is a rotating disc. Viscosity is continuously measured (by the torque required to keep the rotor rotating at a constant rate) as a function of time. The temperature is selected to be characteristic of rather severe processing (extrusion, calendering, etc.). 

Mooney viscosimeter n. An instrument invented by M. Mooney in 1924, used to measure the effects of time of shearing and temperature on the comparative viscosities of rubber compounds. It consists of a motor driven disk, tooth-surfaced on the sides, enclosed within a die cavity formed by two halves maintained at controlled temperature and closing force. The specimen is a double disk, joined at the edges and trapped between the die halves and the rotor (ASTM, www.astm.org). 

Once the polymers are manufactured further characterization takes place prior to processing or during the process itself The two key properties that are critical are Tg and Mooney viscosity. The most convenient way to measure the Tg is by differential scanning calorimeter. Mooney viscosity is an industry specific test procedure that is used for assessing the processability of the rubber. Mooney viscosity (ASTM D1646) is measured by rotation of a disk inside a cavity imder pressure. This equipment does not measure the viscosity, but rather the torque required to rotate the disk at 100°C at a rate of 2 rpm. The results are usually given as... 

An interesting development is the TMS (Turner, Moore and Smith—Avon Rubber, Wiltshire, UK) Rheometerwhich is based on a Mooney machine, but the rubber is injected into the closed cavity by means of a transfer pot mounted directly above the cavity. By this means, rubber with freshly created surfaces can be made to fill the cavity and a control maintained on the pressure inside the cavity. This arrangement gives reproducible results at shear rates of up to... 

The Mooney viscometer, used particularly in the rubber industry, is a variant of the cone-and-plate viscometer it restricts the sample to a disk-shaped cavity (ASTM D1646) [4]. 

The Mooney plastimeter is a rotational shearing-disc viscometer (Figure 9.2). The temperature of the machine cavity dies can be preset to typical... 

The TMS rheometer from Negretti is effectively a modification of the Mooney viscometer principle for use with elastomeric materials. The elastomer is introduced into a cavity containing a shearing disc by injection, and measurements of torque under fixed or variable conditions of temperature and rotor speed can be made. Effective simulation of a variety of process conditions can be made. The instrument has found particular use in the investigation of rubber-to-metal adhesion behaviour, a problem of importance to mould fouling and extrusion processing. 

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. 

Mooney Viscosity, Mooney Scorch, Cure Index - The Mooney Viscometer is widely used throughout the rubber industry as a standard instrument for determining the relative viscosity of rubber and rubber-like materials in the raw or compounded (but uncured) state. It is also used for determining the curing characteristics of vulcanizable compoimds. The viscometer measures the force, or torque, required to rotate a metal disk, or rotor, within a shallow cylindrical cavity filled with rubber compound (ASTM D-1646). 

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