Torque-time curve

FIGURE 11.8 Torque time curves for two-step reaction. (From Naskar, M., Debnath, S.C., and Basu, D.K., Rubber Chem. TechnoL, 75, 309, 2002.)... 

The vane yield stress technique is a useful technique that applies small deformations in the initial stages and large deformations in the latter stages. From the initial linear portion of the torque-time curve at a low shear rate, for example, 0.01 s , the shear modulus (G) can be calculated as ... 

The area under the torque-time curve is related to the energy of mixing and can be used as an end-point parameter. Area under power consumption curve divided by the load gives the specific energy consumed by the granulation process. This quantity is well correlated with the relative swept volume. ... 

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

Figure 1. Torque-time curve for dispersion process using Figure 2. Torque-time curve for dispersion process using technique A (T=170°C and 20 rpm). pure HOPE, technique A (samples with surfactant treatment, T=170°C HDPE-Ti02, AHDPE-Ti02/A0T. 20 rpm). A50%, o 30%, 15%.

Figure 3. Torque-time curve for dispersion process using Figure 4. Torque-time curve for dispersion process of artificial technique B (T-170°C and 20 rpm). 50% Ti02, 50% agglomerates using technique A (pag =1.61 g/cm T=170°C, Ti02/AOT. and 20 rpm). 30% Ti02, 30%TiO2/AOT.

The torque - time curve for the technique (B) is presented in Figure 3. It can be observed higher torque at the peak for the non-treated powder. 

Figure 5. Dimensionless torque-time curves for dispersion Figure 6. Viscosity as function of frequency at T 200 C. process of artificial agglomerates using technique A (paggi=1.61 P HDPE, HDPE-30% Ti02, HDPE-30% Ti02/A0T.

The melt processing characteristics of dynamic vulcanized HDPE/NR/TPS blends have been studied from the processing torque-time curve. Figures 10.1(a) and (b) show the processing torque of the melt mixed sulfur and... 

Figure 18.5 shows comparative torque time curves for NR/HDPE blends at a fixed blend ratio of 80/20 with three types of blend compatibilizers added. It can be seen that the torque increased in the absence of a compatibilizer. Also, the phenolic resin with active hydroxymethyl (methylol) groups gave the highest mixing torque at the final mixing stage. 

Figure 18.6 Torque-time curve obtained during blending of PP/EPDM/NR and PP/ EPDM/ENR25.

Figure 18.48 Torque-time curves for ENR-30/PMMA blends.

Figure 18.49 Torque-time curves for 60/40 ENR/PMMA blends with various ENRs.

Figure 5.25 A typical torque-time curve generated in an internal mixer during compounding of fillers into polymers. (Reprinted from Ref. 91 with kind permission from Marcel Dekker, Inc., New York, USA.)...

The torque-time curve was initially somewhat irregular due to the lateral extrusion of some of the sample material during the first few cycles of anvil oscillation. Data was taken after the torque-time curve had stabilized and approximated a square wave. A typical tracing obtained on PP is shown in Fig. 1. Note that during the experiment the rotation speed was increased about 5 fold with no apparent residual effect on the sample. There was only a small increase in torque associated with the higher strain-rate or sliding speed. This is typical of what has been observed with other polymers studied . 

Figure 3.25. Torque-time curves of PP based nanocomposites recorded during melt compounding (content of nano-silica = 1.36 vol%)...

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]. 

The torque-time curves recorded at various rotational speed of a rheometer are shown in Figure 4.6 for a sample of gum rubber. 

Some time ago another characterisation method was developed utilising a transient shear measurement at a very low deformation rate [22]. In the present study this method is used to discriminate between the samples. Figure 12.16 shows torque-time curves, which were obtained with a rotational rheometer with a biconical rotor [23] at a rotational speed of 0.045 rpm. 

Figure 12.16 Torque-time curves at a very low deformation rate, indicating gel and long branch formation at rotor speed 0.045 min. ...

There are two aspects in the question of uniformity. The first one is a black swan , so-to-speak. If the specification is for the shape of the bird, a black one will not be noticed. This is illustrated in Figure 13.2, by two torque-time curves obtained in the usual Mooney index measurements [2]. These two rubbers give exactly the same torque at 4 minutes of the rotation, e.g., ML (1+4), and yet their behaviours are very different. If the specification is the value of ML (1+4) only, the black swan goes unnoticed. 

Figure 13.3 Mooney torque-time curves showing permissible range of processability.

Other indicators to monitor are the torque-time curve and the movement of the ram. Also, pressure tapping may be explored. Before discussing these, it is worthwhile to examine some of the causes of time-wise reproducibility problem. Even if the charging of the material is done in the same way each time, the mutual positions of two rotors with respect to wings are not the same. If there is a difference in the rotational speed of the rotors, they meet at the same mutual position after so many revolutions. The question is whether or not the charging may be automated in such a way for the rotors to accept the material at the same mutual position every time. 

The amplitude of oscillation in torque-time curve or that of the ram movement decreases as the contents becomes more homogeneous. In order to use these or total energy for deciding the endpoint, the dispersion must be examined ahead of time to assure a satisfactory result. The reproducibility in the same type mixer but different machines may be a problem. There may be a difference in the extent of wear of the rotor blades. The cooling surface may have scale build-up such that the cooling efficiency may be different. 

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. 

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