Torque—temperature curve

Of course, it is of great interest to determine the kinetic parameters from the torque-temperature curves obtained with the MDR run in scanning mode. These parameters can be calculated from the curves shown in Figure 3.18 by using either the method based on Equation 3.11, called the Freeman-Carroll method, or the simple method based on fitting the parameters in Equation 3.19. 

Fig. 12 Time-torque curves for master batch preparations with XNBR and organoclay in the internal mixture at 160°C and 50 rpm rotor speed (a). Time-temperature curves for master batch preparations with XNBR and organoclay in the internal mixture at 160°C and 50 rpm rotor speed (b)...

Another reason may come from a different thickness of the rubber sample. The torque-time curves obtained with these two apparatus shown in Figure 3.11 clearly show this strong difference. All these two apparatus work under isothermal conditions. Thus the MDR is used at three temperatures to allow evaluation of the kinetic parameters of the cure reaction. 

FIGURE 6.1 Torque -time (temperature) curves obtained with the oscillating disc rheometer (ODR) and the moving disc rheometer (MDR). 

The development of models based on kinetic, thermodynamic and rheological equations to calculate degree of dispersion, batch temperature and relative batch viscosity at intervals during a mix cycle in an internal mixer is described. Predicted values based on the models are discussed in comparison with experimental torque and temperature curves for mixing natural rabber with carbon black over a wide range of compositions at various rotor speeds. 19 refs. 

The interaction between machine and material is manifested in the temperature-rise, the torque-time curve and the cumulative energy input. Here, we will discuss the torque-time curve, see Figure 3.6 [1]. 

Van Buskirk et al. claimed that the flow behaviour of SBR-black compounds was a function of mixing work input. Flow behaviour was independent of mixer size, speed and mixing time as long as the temperature-time profiles were identical. From this they introduced the unit work concept. In a later paper Turetzky et al. suggested that rather than using the second peak of the torque-time curve as in the BIT test described above, it would be more appropriate to take a later point on the torque-time curve, the so-called t point. The position of this t point is illustrated in Fig. 1. 

Plasticity can be studied using a device known as the Gieseler plastometer. A constant torque is appHed to a shaft with rabble arms imbedded in coal in a cmcible heated at a fixed rate. The rate of rotation of the shaft indicates the duidity of the coal and is plotted as a function of the coal temperature. These curves, as shown in Figure 8, have a well-defined peak for coking coals usually near 450°C. Softening occurs at 350—400°C. At a normal heating rate of 3°C/min, the duid hardening may be complete by 500°C. 

Figure 6 shows a typical plastogram in the form of curves showing torque variations versus time. Also shown here is the curve of the variation of the material temperature versus time in the instrument s working chamber. We can see the following characteristic regions. At point A, the lumping process and the formation... 

The sticky point can be determined by using a method developed by Lazar and later by Downton [Downton, Ffores-Luna, and King, "Mechanism of Stickiness in Hygroscopic, Amorphous Powders, Ih-EC Fundamentals 21 447 (1982)]. In the simplest method, a sample of the product, at a specific moisture, is placed in a closed tube which is suspended in a water bath. A small stirrer is used to monitor the torque needed to stir the product. The water bath temperature is slowly increased until the torque increases. This torque increase indicates a sticky point temperature for that specific moisture. The test is repeated with other product moistures until the entire stickiness curve is determined. A typical curve is shown in Fig. 12-23. 

Figure 10.1. Schematic representation of the processing window for the extrusion process. The four curves identify limits to the process Une 1 indicates the maximum screw rotation speed, curve 2 represents the torque limitation of the drive system (region to the right and below of curve exceeds the allowable torque on the drive system), curve 3 represents the maximum temperature allowable to avoid the thermal degradation, and Une 4 shows the minimum screw rotational speed to provide the minimum throughput, acceptable by the process economics.

The other purpose was to evaluate mathematically the torque change as a function of temperature, as well as the kinetic parameters from this curve. Moreover, the profiles of... 

The value of the torque at time t, Y as a fraction of its maximum value, expressed in percent, is drawn as a function of the die temperature. The curves are shown in Figure 3.18 for various values of the heating rate ranging from 2 to 10°C/min. Calculation is made using Equation 3.20 and the values collected in Tables 3.3 and 3.5. 

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