Effect Payne

In the design of rubber as a material of construction to meet specific application requirements, the engineer has to first understand the limitations of the physical and functional properties of the rubber material, in order to avoid using the same, to stresses (applied 

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In addition to increases in high-strain loss modulus, reductions in low-strain loss modulus are also observed. This may be attributed to the improvements in polymer-filler interactions which may reduce the amount of filler networking occurring in the compound. The low-strain losses are dominated by disruptions in the filler-filler network, the Payne effect. 

The morphology of the agglomerates has been problematic, although some forms of network-like structures have been assumed on the basis of percolation behavior of conductivity and some mechanical properties, e.g., the Payne effect. These network stmctures are assumed to be determining the electrical and mechanical properties of the carbon-black-filled vulcanizates. In tire industries also, it plays an important role for the macroscopic properties of soft nano-composites, e.g., tear. 

FIGURE 22.6 Payne effect of butyl composites with various amounts of N330, as indicated (left) [28]. Scaling behavior of the small-strain modulus of the same composites right). The obtained exponent 3.5 confirms the cluster-cluster aggregation model. (From Kliippel, M. and Heinrich, G., Kautschuk, Gummi, Kunststoffe, 58, 217, 2005. With permission.)... 

FIGURE 28.24 Plots of Payne effect of composites filled with different contents of Mg(OH)2. (From Zhang, Q. et al J. Appl. Polym. Set, 94, 2341, 2004.)... 

Above a critical hller concentration, the percolation threshold, the properties of the reinforced rubber material change drastically, because a hller-hUer network is estabhshed. This results, for example, in an overproportional increase of electrical conductivity of a carbon black-hUed compound. The continuous disruption and restorahon of this hller network upon deformation is well visible in the so-called Payne effect [20,21], as represented in Figure 29.5. It illustrates the strain-dependence of the modulus and the strain-independent contributions to the complex shear or tensUe moduli for carbon black-hlled compounds and sUica-hUed compounds. 

The incorporation of reinforcing hllers into rubber results in most cases in an increase of the storage and loss moduli, G and G", and an increase in hysteresis, as quantihed by the loss angle 8, where tan 8 is C jG. When properly dispersed and coupled to the mbber matrix via a coupling agent, as represented by a low Payne effect, silica also shows less hysteretic loss at elevated temperatures. 

Dynamic measurements of the uncured compounds were also performed with the aid of the RPA 2000 at 100°C and a frequency of 0.5 Hz. The Payne effect was measured as the storage modulus G at a low strain of 0.56%. 

FIGURE 29.11 Effect of silanization in an open mixer on the Payne effect for different mixer types and fill factors (silanization time 150 s, temperature 145°C, T4 tangential 3.6 L, 15 intermeshing 5 L, 145 intermeshing 45 L, T7 tangential 7 L). 

Figures 29.11 and 29.12 demonstrate the results of the silanization efficiency for different mixers and different fill factors under standard conditions (closed mixer) compared to working with an open mixer. The silanization efficiency is measured by viscosity and Payne effect.

Another measure to improve the removal of ethanol is air injection into the mixer during the silanization step. Air can be injected from the bottom part of the mixer using existing valves without any special outlet for the injected air. In these experiments air injection is switched on once the compound reached the silanization temperature (145°C) and the rotor speed is adjusted in order to maintain the silanization temperature. Figure 29.13 shows the properties of this compound compared to a compound that was silanized under the same conditions except with air injection switched off. Air injection lowers the Payne effect, Mooney viscosity, and water content in the compound, and ethanol removal is more effective. All other properties are comparable to the properties of a standard silica compound. 

The interaction between two fillers particles can be investigated by measuring the Payne effect of a filled rubber compounds. In this measurement, dynamic properties are measured with strain sweep from a very small deformation to a high deformation. With the increased strain, the filler-filler network breaks and results in a lower storage modulus. This behavior is commonly known as the Payne effect... 

The strain dependence of the elastic storage modulus of clay-filled NBR has been measured and the results compared with those of unfilled vulcanizates. The corresponding data are shown in Fig. 19. From this figure it is revealed that there is no Payne effect, because the G values do not decrease with the increase in strain... 

Filler-filler interaction (Payne effect) - The introduction of reinforcing fillers into rubbery matrices strongly modifies the viscoelastic behavior of the materials. In dynamic mechanical measurements, with increasing strain amplitude, reinforced samples display a decrease of the storage shear modulus G. This phenomenon is commonly known as the Payne effect and is due to progressive destruction of the filler-filler interaction [46, 47]. The AG values calculated from the difference in the G values measured at 0.56% strain and at 100% strain in the unvulcanized state are used to quantify the Payne effect. 

The Payne effect of S-SBR compounds filled with untreated silica, PA-, PPy-, and PTh-silicas, and silane-modified silica are shown Fig. 17. 

Compounds containing PA-silica, PTh-silica, or silane-treated silica show the lowest reinforcement parameters in this series. This indicates a good dispersion of the polymer and a low degree of filler-filler interaction, as also shown by the Payne effect values. 

The Payne effects of S-SBR/EPDM blend filled with untreated silica, plasma-modified silicas, and silane-treated silica are shown in Fig. 22. 

The blends containing PA-silica and PTh-silica (samples SEPA and SEPTh, respectively) show the highest Payne effect values of all samples. The silane-modified silica shows the lowest filler-filler interaction compared to all other silicas. 

The Payne effect values of the plasma-coated carbon black at various filler loadings in SBR are shown in Fig. 27. The plasma-coated carbon black shows a lower Payne... 

Fig. 27 Payne effect of fullerene carbon black (FS) and plasma-coated fullerene carbon black (PCFS) in SBR at increasing loadings...

Fig. 29 Payne effect of carbon blacks in SBR, EPDM, and a 50 50 SBR/EDPM blend...

With the uncoated carbon black, the Payne effect in the SBR/EPDM blend positions itself between those of pure SBR and EPDM. For the plasma-coated carbon black, the blend has a Payne effect value comparable to that of EPDM, at a significantly higher value than the SBR compound (Fig. 29). 

For silica in SBR, a polyacetylene coating gives the lowest filler-filler interaction, a good filler-polymer interaction, and the best dispersion compared to untreated and the other plasma-treated samples. However, for the stress-strain properties, the polythiophene-treated sample gives the best results. This shows the importance of sulfur moieties on the surface of the filler, which form a secondary network in the cured materials. In the blend of S-SBR and EPDM rubbers, the situation is less conclusive. The Payne effect, the bound rubber, and... 

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