Rheometer torque

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). 

When 4-(mercaptoacetamido)diphenylamine [60766-26-9] (39) is added to EPDM mbber and mixed in a torque rheometer for 15 minutes at 150°C, 87% of it chemically binds to the elastomer (24). The mechanical and thermal stress placed on the polymer during mixing mptures the polymer chain, producing radicals that initiate the grafting process. 

TR torque rheometer XLPE cross-linked polyethylene... 

Figure 14. Schematic representation of the torque rheometer, adapted from Tardos (1994).

Hellen L, Yliruusi J. Process variables of instant granulator and spheroniser III. Shape and shape distributions of pellets. Int J Pharm 1993 96 217-223. Chapman SR, Rowe RC, Newton JM. Characterization of the sphericity of particles by the one plane critical stability. J Pharm Pharmacol 1988 40 503-505. Rowe RC, Sadeghnejad GR. The rheology of mcc powder/water mixes-measurement using a mixer torque rheometer. Int J Pharm 1987 38 227-229. O Connor RE, Schwartz JB. Spheronization II Drug release from drug-diluent mixtures. Drug Dev Ind Pharm 1985 11 (9-10) 1837-1857. 

ASTM D3795, Test Methodfor Thermal Flow/ Cure Properties of Thermosetting Plastics by Torque Rheometer, Vol. 8.02, ASTM, Philadelphia, Pa., 1993. 

The use of Brabender torque rheometer enabled us to evaluate the behavior of melt viscosity vs. time at low shear stresses the usual operating conditions were adopted—i.e., granules (28 grams) were introduced in the bowl, the temperature was fixed at 187 °C, and each run was started after 5 minutes of conditioning. 

Treatment of PVC, suspended in chlorobenzene, with Et2AlCl followed by the addition of methanol greatly improved the thermal stability (6). This will be the subject of a separate publication. However, the nature of the improvement was different—i.e., film pressed in air at 200°C was yellow not colorless, but processing stability as determined by the torque rheometer test in the Brabender Plasticorder at 195°C was far superior and was measured in hours rather than minutes. The removal of labile chlorine atoms by Et2AlCl undoubtedly contributed to heat resistance. However, in the absence of a further reaction, such dehalo-genation probably became dehydrohalogenation, contributing to color development. 

The high level of unsaturation in the cw-1,4-polybutadiene per se and after dehydrochlorination as well as the unsaturation generated in the PVC has its drawbacks in the potential susceptibility to crosslinking. This may be responsible for the unexpectedly small improvement in the processibility of the cw-l,4-polybutadiene PVC graft copolymer, as indicated by the torque rheometer test. 

Torque rheometers are multipurpose instruments well suited for formulating multicomponent polymer systems, studying flow behavior, thermal sensitivity, shear sensitivity, batch compounding, and so on. The instrument is applicable to thermoplastics, rubber (compounding, cure, scorch tests), thermoset materials, and liquid materials. 

The torque rheometer with a twin-screw extruder is considered a scaled-down continuous compounder. It allows the compounding engineer to develop polymer compounds and alloys. It also permits the formulation engineer to assure that the formulation is optimum. 

The torque rheometer is essentially an instrument that measures viscosity-related torque caused by the resistance of the material to the shearing action of the plasticating process. 

The prevalent design is a microprocessor-controlled torque rheometer. The system consists of two basic units an electromechanical drive unit and a microprocessor unit. The basic system is shown in Figure 7. 

Simulation of the extrusion process in the laboratory is one of the most important applications of the torque rheometer in conjunction with single-screw extruders. Figure 13 illustrates simulations of widely used extrusion processes in the industries. 

Carboxylic elastomers have been reinforced with cationic starch products.93 Compounds were prepared either by solution mixing followed by drying, or by using a torque rheometer. The addition of cationic starch significantly reduced the toluene solubility of the carboxylated rubber. Physical properties of these compounds were greater than compounds prepared with unmodified pearl starch. 

The apparatus used for the first tests included a 3/4-inch diameter, 20 1 L/D laboratory extruder. The second series of evaluations was run on a Brabender torque rheometer equipped with mixing head. The third tests utilized large scale processing equipment including a two-roll,... 

Some of the test methods being used to measure the processing stability of polypropylene include melt flow drift measurements at elevated temperatures using an extrusion plastometer (melt indexer), melt viscosity retention measurements using a torque rheometer, retention of melt flow after repeated extrusions, and injection molded spiral test measured by the flow in inches at various temperatures and the retention of melt flow of the injected spirals. The nine commercial resins were evaluated by these methods. 

Torque Rheometer. The Brabender plastograph was also used to study the relative processing stabilities of the polymers. The conditions were those recommended by P. G. O Leary (24). The melt viscosity-time curves are shown in Figure 10. Resins D, I, and E are the least stable, and A, H, G, and B are the most stable. 

A torque rheometer is a device that provides an off-line measurement of torque required to rotate the blades of the device and this torque can be used to assess rheological properties of the granulation. It has been extensively used for end-point determination.The torque values thus obtained were termed as measure of wet mass consistency. ° ... 

One of the main concerns is that using the torque value that the imit is reporting instead of the dynamic viscosity for calculation of Reynolds numbers renders the latter to become dimensional. Therefore, the Reynolds number calculated from torque rheometer data is referred to as pseudo-Reynolds dimensional number. Because of the fact that torque was shown to be proportional to a kinematic (rather than dynamic)... 

Another concern is the interpretation of data from mixer torque rheometer that was used to assess the viscosity of wet granulation. The torque values obtained from the rheometer were labeled wet mass consistency and were used instead of dynamic viscosity to calculate Reynolds numbers. It was shown that such torque values are proportional to kinematic... 

Landin, M. Rowe, R.C. York, P. Characterization of wet powder masses with a mixer torque rheometer. 3. Nonlinear effects of shaft speed and sample weight. J. Pharm. Sci. 1995, 84/5, 557-560. 

Rowe, R.C. Sadeghnejad, G.R. The rheological properties of microcrystalline cellulose powder/water mixes-measurement using a mixer torque rheometer. Int. J. Pharm. 1987, 38, 227-229. 

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