Silica compounds 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 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 modification of the silica surface activity is obtained via silanization in situ, which has been used to reduce the silica polarity. As expected, it was observed a reduction in the G and in the Payne effect as the silanization takes place in the precipitated silica. Analyzing the dependency of G as function of deformation amplitude to the compound SBR-2/sUica/silane, it can be seen that the silanization leads to a decrease of 2.5 ties of the G value in comparison to the reference compotmd. However, it should be noticed that first, the reduction of the Payne effect is remarkably lower than that obtained to the SBR-2(ep7) and non sUanized silica compound and, second, the value of G obtained to SBR-2(ep7) and sUanized silica is comparable to the SBR-2/sifica/silano system. 

The nonlinear viscoelastic behavior of the composites of natural rubber filled with surface-modified nanosilica was studied with reference to silica loading [191]. The effect of temperature on the nonlinear viscoelastic behavior has been investigated. It was observed that Payne effect becomes more pronounced at higher silica loading. The filler characteristics such as particle size, specific surface area, and the surface structural features were found to be the key parameters influencing the Payne effect. A nonlinear decrease in storage modulus with increasing strain was observed for unfilled compounds also. The results reveal that the mechanism includes the breakdown of different networks namely the filler — filler network, the... 

The incorporation of fillers to elastomeric compounds strongly modifies the viscoelastic behavior of the material at small strains and leads to the occurrence of a non-linear behavior known as Payne effect [49] characterized by a decrease in the storage modulus with an increase in the amplitude of small-strain oscillations in dynamic mechanical tests. This phenomenon has attracted considerable attention in the past decade on account of its importance for industrial applications [50-54]. The amplitude AG = G q—G ) of the Payne effect, where G q and G aie the maximum and minimum values of the storage modulus respectively, increases with the volume fo-action of filler as shown in silica-filled PDMS networks (Figure 4.7a). At a same silica loading, the PDMS network filled with untreated silica displays a much higher G value than the treated one and is much more resistant to the applied deformation (Figure 4.7b). 

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