OSCILLATING-DISC

FIGURE 28.2 Standard oscillating disc curemeter curve. (Redrawn from Andrew, C., Introduction to Rubber Technology, Knovel e-book publishers, 1999.)... 

The surface viscosity varies significantly along the isotherm and across monolayer phase boundaries. Addition of subphase metal ions increases the surface viscosity drastically, as was recently reinvestigated [36]. Recently, microscopy methods have been used to image velocity profiles of different monolayer phases flowing through a narrow channel, such as used in the canal viscometer [37], The two main methods used to study monolayer viscosity are the canal viscometer and the oscillating disc method [8,9]. 

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. 

The surface viscosity, T s gram/second, was investigated by the oscillating-disc method. It was found that low iis (0.03-0.08 g/s) beer surfaces presented a nongushing behavior. Beers with high ps (2.3-9.0 g/s) presented a gushing behavior. 

Mention was made above that oscillating die curemeter based instruments are now widely used for obtaining measures of processability. In fact, the other types of curemeter considered in Section 4, oscillating disc,... 

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. 

Figure 6-7. Principles of oscillating disc and oscillating die curemeters. (a) Oscillating disc ...

ISO 3417, 1991. Method for the determination of vulcanisation characteristics using an oscillating disc curemeter,... 

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

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. 

The results of viscosity measurements with liquid He-II show that the flow is composed of a part which is proportional to the pressure and depends on the viscosity according to Poiseuille s law, and another part ( superflow ) independent of pressure and apparently without any frictional resistance. In very fine tubes the first part is negligible. The results with capillary tubes and oscillating discs are different. 

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 ... 

Figure 1. Cure response by oscillating disc rheometry at 177 °C of a compound optimized for use In o-rlngs.

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. 

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. 

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. 

Curemeters, oscillating disc, and reciprocating paddle types are forms of plastimeter that measure plasticity before the onset of cure, as well during the cure. The viscoelastic behavior of uncured rubber tested by dynamic measurement is characterized by in-phase and out-of-phase moduli and loss tangent. 

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. 

The British standard, BS 1673, Part 10 [8] covers reciprocating paddle, as well as oscillating disc curemeters. 

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... 

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