Torque measurement rheometers

A development of the moving die rheometer where the operation of the unit is fully computer controlled. The rate of oscillation, temperature and level of strain can all be run through a series of options. The torque measurements are also highly sophisticated. As a consequence, the unit can be set up to monitor processing parameters, then the cure behaviour and finally the finished dynamic properties of the cured material. It is manufactured by Alpha Technologies. 

TABLE Torque measurement ranges for Brookfield YR-1 Rheometer. 

Onufer RJ (1968) Characterization of clay plasticity with a torque measuring rheometer. In Rutgers University, Rutgers School of Ceramics, New Brunswick, New Jersey, October 5, 1968 - Brabender OHG Literaturver-zeichnis Nr. 352... 

In bromobutyl/chlorobutyl rubber blends, both elastomers have the polyisobutylene backbone and halogen reactive functionality. These polymers, being molecularly miscible, constitute an ideal system for co-vulcanization. Bromobutyl and chloro-butyl can be used interchangeably without significant effect on state of cure as measured by extension modulus, tensile strength, and cure rheometer torque development. Bromobutyl will increase the cure rate of a blend with chlorobutyl. However, where bromobutyl is the major part of the blends, chlorobutyl does not reduce scorch tendencies because the more reactive halogen unit can dominate. 

Fig. 7.14. Standard arrangements used for the characterization of shear flows (left) and extensional flows (right). Shear viscosities can be derived from the torque measured in a cone-and-plate rheometer the primary normal stress difference is deduced from the axial force. Elongational viscosities follow from the tensile force required for the drawing of a molten fibre in the tensile rheometer, as monitored by a leaf spring...

Chapters S and 6 have described and evaluated the important shear rheometers and indexers. If measurements of torques, forces, and velocities or pressures and flow rates are made and interpreted properly, all these rheometers should measure the same shear material functions. To conclude these two chapters, we make a few comparisons between rheometers to emphasize this point. Table 6.5.1 highlights some of the strengths and weaknesses of each. 

There are two basic designs of drag flow rheometers controlled strain with stress measurement and controlled stress with strain measurement. Below we Hrst discuss strain control and torque measurement (Section 8.2.2) followed by instrument alignment problems (Section 8.2.3) and normal stress measurement (Section 8.2.4). Then we treat special design issues for stress control. Both designs use the same type of environmental control system, as discussed in Section 8.2.6. 

Schematic diagram of an open loop, controlled stress rheometer. Torque is provided by a drag cup motor, and motion is measured with an optical encoder. Designs similar to this are used by Bohlin, Carri-Med, Haake, and Rheometrics.

In the newly developed units, the dynamometer is mounted together with the high-precision electronic torque-measuring unit on a stable and distortion-free base plate. The torque of the linear dynamometer is measured directly using a load cell without any intermediate member, thereby increasing the overall reliability of the torque rheometer. 

Techniques for evaluating processing stabiHty and mechanochemical effects include using a Brabender torque rheometer (29,30), injection mol ding (26,28), capillary rheometry (26,28), and measuring melt index as a function of residence time (26). 

Fig. 29. Measurements of yield stress with a vane device and Rheometrics controlled stress rheometer. The torque required to cause yielding is between 1.88...

Specific Commercial Rotational Viscometers. Information on selected commercial rotational viscometers can be found ia Table 7. The ATS RheoSystems Stresstech rheometer is an iastmment that combines controlled stress as well as controlled strain (shear rate) and oscillatory measurements. It has a torque range of 10 to 50 mN-m, an angular velocity range of 0 to 300 rad/s, and a frequency range of seven decades. Operation and temperature programming (—30 to 150°C higher temperatures optional) are computer controlled. 

In order to test this concept a series of compounds was prepared in a 5 L Shaw Intermix (rubber internal mixer, Mark IV, Kl) with EPDM (Keltan 720 ex-DSM elastomers an amorphous EPDM containing 4.5 wt% of dicyclopentadiene and having a Mooney viscosity ML(1 +4) 125°C of 64 MU 100 phr), N550 carbon black (50 phr), diisododecyl phthalate (10 phr), stearic acid (2 phr), and l,3-bis(tert-butylperoxy-isopropyl)benzene (Perkadox 14/40 MB ex Akzo Nobel 40% active material 6 or 10 phr). A polar co-agent (15 phr) was admixed to the masterbatch on an open mill and compounds were cured for 20 min at 180°C in a rheometer (MDR2000, Alpha Technologies). The maximum torque difference obtained in the rheometer experiments was used as a measure of... 

The viscosity of a liquid can also be determined by measuring the torque needed to rotate a cylinder in the liquid. Brookfield viscometers and rheometers fall into this class of instrument (Fig. 3.7). The viscometer measures the torque produced when a spindle is rotated at constant velocity in a liquid. The Rheometer produces a constant torque... 

Figure 20.2 Torque value as a function of PHB content for PHB/PEN/PET ternary blends measured at 285 °C and a constant rpm of 60 using a Haake rheometer molar ratio of PEN to PET of 1 1...

---