ABSTRACT
The temperature measurements were conducted at deformation cycle between 0% and 200% strain at 25 °C for unfilled SBR and filled SBR, which is shown in Figure 2. The solid line and dotted line show the filled and unfilled SBR respectively. The values of temperature change, ΔT, were calculated by the difference from the initial temperature of rubber specimens. The temperature increases with increasing strain at stretching process and decreases with decreasing strain at un-stretching. The temperature increases with increasing strain at stretching process and decreases with decreasing strain at un-stretching for the un-filled SBR. The similar temperature change was found in the filled SBR, but the continuous increase in the base line of temperature can be seen. The amplitude of the peak-to-peak temperature is 1.25 K for the filled SBR and 0.6 K for the unfilled SBR. The strain amplification factor, X, was calculated to derive the extension ratio, α′, appropriate to the SBR phase [Mullins 1969]. The value of X was defined under the rubber adhering to the filler surfaces and the absence of deformation in the fraction of the material composed of filler. The shape of filler is also assumed to consist essentially of spherical particle. The work done on the SBR phase was also calculated for unfilled and filled SBR. It shows that the local strain energy of rubber phase in the filled SBR is twice larger than that of unfilled SBR at 200% strain. The simplest interpretation of this result is that the amplitude of the peak-to-peak temperature can be associated with the work done on the SBR phase strained by the magnitude of the strain amplification factor due to the presence of filler. The ratio of them is approximately a factor of two, which shows a good agreement with the ratio of work done on SBR phase of unfilled and filled. This calculation was assumed that the shape of filler particle is sphere and there are no filler networks and the trapped rubber inside them. But it was reported that only 33% clearly dominates the overall strain energy at the small strain up to 15%. This means that the remaining 67% has little effect on the overall strain energy. For the rubber with perfectly dispersed fillers, 60% rubber is responsible for the total strain energy [Akutagawa 2008]. At 200% strain the filler network is collapsed and the trapped rubber may disappear. This is due to the
fact that the temperature change of filled SBR is well represented by the strain amplification.
