Meter, cure

Continuous measurements with the help of cure meters. 

In all the above methods, it is necessary to cure specimens of test samples for each of a series of curing times and then perform the desired test on the vulcanizate. However, in the test for continuous measurement of vulcanization complete information could be obtained with saving in time. The mooney viscometer test approaches this objective. However a weakness of the mooney viscometer test is that the test is completed before a measurable modulus value after the scorch point has been obtained. This is because the test sample is destroyed after the induction period is passed due to tearing by continuous rotation of the rotor whether small or large. To overcome this deficiency and to provide a total cure curve for the entire vulcanization cycle, a series of instruments called cure meters was developed. In each of these instruments the stiffness or modulus of the compound was chosen as parameters for vulcanization continuously. The Vulkameter developed by Bayers, Germany was the first of the cure meters developed. 

Dynamic mechanical analysers, as discussed in chapter 9, can be constructed so that they can be used with unvulcanised materials and, hence, the in phase and out of phase components of modulus and the loss angle measured. The usual test piece geometries for cured rubbers are not convenient for the uncured materials where some form of oscillating shear is probably the best approach. This is the geometry used in cure meters discussed in the next section and such instruments have formed the basis for apparatus which measures dynamic properties from before and through the curing process. 

ASTM D2084, 2001. Vulcanisation using oscillating disc cure meter. 

BS903 Pad A60-2, 1992. Method for the determination of vulcanisation characteristics using an oscillating disc cure meter. 

ASTM D5289, 1995. Vulcanisation using rotorless cure meters. 

The time required for gellation can be converted into energy by using a spot cure meter that measures and displays the intensity of the UV emitted within the bandwith 320-390 nm. Different formulations have been characterized using this apparatus. 

Laboratory measur ent of curing characteristics have been somewhat revolutionized by the introduction of the cure meters. There were two types of cure meter the reciprocating paddle type as in the Wallace-Shawbury curometer, and the oscillating disc type such as the Monsanto rheometer. In the oscillating disc type (ODR) a biconical disc is embedded in the rubber in a closed cavity. The disc is oscillating through constant angular displacement, and the torque required monitored. 

D 2084 Standard test method for rubber property- Vulcanization using o.scillation disk cure meter. Annual Book of ASTM Standards. Vol. 09 01. 1996. p. 365. 

Both the rate of vulcanization after the scorch period and the final extent of vulcanization are now measured by using devices called cure meters. Many researchers have contributed to this development (Decker et al., 1963 Juve et al., 1964). Widely used cure meters are oscillating disc rheometers of the type introduced by the Monsanto Company around 1965. The development of the oscillating disc rheometer, largely through the efforts of Wise, was the beginning of modern vulcometry, which has become standard practice in the industry. Before the development of the cure meter, it was necessary to measure... 

Newer versions of the cure meter have been introduced (e.g.. Figure 7.6). The cavity is much smaller and there is no rotor. In this type of cure meter, one-half of the die (e.g., the upper half) is stationary and the other half oscillates. These instruments are called moving-die rheometers. The sample is much smaller and heat transfer is faster. Also, because there is no rotor, the temperature of the cavity and sample can be changed more rapidly. In either case (oscillating disc or moving die), torque is automatically plotted against time. Such a chart is shown in Figure 7.7. 

The cure curve gives a rather complete picture of the overall kinetics of crosslink formation and even crosslink disappearance (reversion) for a given rubber mix. In some cases, instead of reversion, a long plateau or marching cure can occur. The cure meter is, therefore, extensively used to control the quality and uniformity of rubber stocks (also called rubber compounds). 

Vulcometry started as a research tool to study vulcanization. It was then used to control uniformity of rubber mixed in the factory. Also, programmed temperature-profile vulcometry has been used to develop recipes for industrial use. The cure temperature-time profile of an industrial mold can be imposed on the curing cavity of the cure meter. The test sample can then be vulcanized in... 

Both the rate of vulcanization after the scorch period and the final extent of vulcanization are measured by devices called cure meters. The development of the oscillating disc rheometer was the beginning of modem vulcometry, which is the standard industrial practice. 

Standard Test Method for Rubber Property— Vulcanization Using A Rotorless Cure Meter (ASTM D5289-95). 

Rheometer a cure meter which determines and plots a cure curve, illustrating the state of cure for a given time and temperature typically either an oscillating disk rheometer (ODR) or a moving die rheometer (MDR). 

---