Oscillating disc rheometers

Alpha Technologies) Oscillating Disc Rheometer. Other rheometers are the Yarsley piston rheometer and the capillary rheometer. 

The degree of vulcanisation of a rubber compound is assessed technically by the indefinite terms of undercure, correct cure, optimum cure and overcure. It may be given precision by (a) measurement of stress-strain relationship of a range of cures, (b) measurement of the modulus at 100% elongation, (c) measurement of the volume swelling in benzene, or (d) by the use of instruments such as the oscillating disc rheometer and the moving die rheometer. 

If a fully compounded thermosetting rubber is subjected to a plasticity measurement at a high enough temperature and for long enough, it will cure and, consequently, there is not always a clear distinction between a plasticity test and a test for scorch or rate of cure. For example, the Mooney viscometer is used to measure scorch, i.e. the onset of vulcanisation, and an oscillating disc rheometer will measure the plasticity of the compound before the onset of cure as well as the increase in stiffness as curing takes place. 

Materials. Two types of standard tire cord obtained from Gen Corporation were used in this investigation polyester, 1300/3, and nylon 66, 1260/3. The rubber composition to which the adhesively dipped cords were bonded had the following composition in parts by weight styrene-butadiene rubber (SBR) 1502, 100 N330 carbon black, 50 zinc oxide, 5 stearic acid, 0.5 sulfur, 1.7 2-morpholinothio-benzothiazole, 2. Master batches were mixed 7 min in a 350-ml Brabender Plasticorder, and curatives were added on a cool two-roll mill. Cure characteristics at 155 °C were determined with an oscillating disc rheometer (ASTM D 2084). The time to reach 90% of the final cure state was 23 min, and the Shore A hardness of the final vulcanizate was approximately 60. 

An interesting, indirect application of the statistical theory to filled rubbers has been published by Wolff (/33). In recent years increasing use has been made of oscillating disc rheometers to follow the course of vulcanization. These instruments operate at low frequencies and at vulcanization temperatures, so that torque recorded at full cure is a good measure of an equilibrium shear modulus and hence proportional to v. Wolff finds for polymers filled with furnace blacks and cross-linked with dieumyl peroxide ... 

Various techniques have been developed in turn the Mooney viscometer, the Wallace-Shawbury curometer, the oscillating disc rheometer (ODR), and the moving disc rheometer (MDR), in addition to the calorimetry techniques. The isothermal calorimetry and its counterpart in scanning mode, the isothermal moving disc rheometer (MDR), and the improvement of this last technique with the rubber process analyzer run in scanning mode, are considered. 

FIGURE 3.11 Torque-time curves obtained with the oscillating disc rheometer (ODR) and with the moving die rheometer (MDR) with the same rubber compound. 

However, as shown in Figure 6.1, tracing the torque as a function of time obtained with the isothermal oscillating disc rheometer (ODR), the temperature of the sample varying with time according to an unknown law, it is not easy to determine the conditions of time and temperature for the scorch of cure, which are associated with the minimum torque value. Moreover, the moving die rheometer (MDR), gives a shorter... 

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... 

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. 

A further instrument, the Rheocheck lOOC, is a classic oscillating disc rheometer offering a full analysis of the vnlcanisation curve with pre-set limits for quality control purposes available from the standard cost-effective computer/printer/plotter package. The instrument can be extended to include a Mooney viscometer. 

The Barco Rheomicro computer package enables existing oscillating disc rheometers to be converted to a powerful dynamic testing system. 

Figure 9.4 Torque versus time curve for an oscillating disc rheometer.

Figure 9.5 Oscillating disc rheometer (Monsanto). The force required to shear the rubber is monitored leading to a complete cure curve of the compound.

Fig. 20 Cure response by Oscillating disc rheometer at 177 °C of a VDF-based polymer cured with Bisphenol-AF (Reprinted with permission of Elsevier) [35]...

Figure 24 [159] is the cure response of an oscillating disc rheometer of the compounds mentioned in Table 17. Figure 24 demonstrates that the rate of crosslinking varies drastically for the industrial peroxides. Efficiencies of P-4... 

The rubber mixes were made by a laboratory two-roll mill at a temperature of approximately 35°C. Mixing of the filler and curing agents with the elastomer was done using selected processing parameters to increase the degree of exfoliation. The condition of vulcanization were determined by oscillating disc rheometer WG-2. The samples were vulcanized at 160°C for the time necessary for a torque increase of rheometric moment by 90% (T0.9). Crosslink density of the vulcanisates was... 

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