The effect of vulcanization additives on the dielectric response of styrene-butadiene rubber compounds

Kinetics of the glass transition of styrene‐butadiene‐rubber: Dielectric spectroscopy and fast differential scanning calorimetry

“…Ortega et al assign the low-frequency broadening of the loss peak as additional mode, and recommend the separation of the two processes applying two Cole-Cole functions. 42 Hence, the complete measured curves in Figure 4(a) can be described by:…”

“…It can be assumed that the dipoles of the DPG couple to the SBR chain segments instead of having an independent relaxation process. 42 The cooling rate dependence of the vitrification process measured by DSC is characterized by the limiting fictive temperature, T f , related to the structure of the glassy state after cooling. 49 At temperatures below the vitrification process, the glass has the same configurational entropy at the sample temperature, T, as a supercooled structurally equilibrated melt at T f > T. From the heat flow curve, Φ(T), T f is determined by considering the extrapolation of the liquid state, Φ l (T), and the glassy state, Φ g (T), according to References 49 and 50: where T rl and T rg are reference temperatures in the supercooled liquid and the glassy state, respectively.…”

“…This asymmetric relaxation peak clearly contains at least two contributions with different temperature dependencies as the peak broaden with decreasing temperature. Ortega et al assign the low‐frequency broadening of the loss peak as additional mode, and recommend the separation of the two processes applying two Cole‐Cole functions 42 …”

“…In contrast to most polymers, the α‐relaxation process of SBR is symmetric 8,41,42 . Thus, the relaxation can be described with β = 1, this is the so‐called Cole‐Cole function: …”

“…The slow mode process occurs due to the presence of the vulcanization accelerator 1,3‐Diphenylguanidine (DPG). It can be assumed that the dipoles of the DPG couple to the SBR chain segments instead of having an independent relaxation process 42 …”