The measurement of differently vulcanized SBR samples by DSC
The samples are described in Section 4.2.2.
Measuring cell: DSC822e with IntraCooler cooling option
Pan: Aluminum standard 40 µl, pierced lid
Sample preparation: Pieces of elastomer weighing approx. 10 mg
DSC measurement: Heating from 70 °C to 50 °C at 5 K/min
Atmosphere: Nitrogen, 50 ml/min
With increasing degree of cross-linking, the glass transition step shifts to higher temperatures. The step height of the glass transition of the elastomer is independent of the degree of vulcanization; the value of Δcp relative to polymer content is 0.39 J/gK. This value is typical for polymers.
The vulcanization system consists of Vulkacit CZ/C and sulfur. The following diagram shows the glass transition temperature as a function of the concentration of sulfur in the formulation.
As has already been shown in Section 4.2.1 with the vulcanization of a technical NBR elastomer, the glass transition temperature of this series of SBR samples also increases with increasing degree of cross-linking. The relatively high degree of cross-linking resulting from the presence of 6.45% sulfur (in sample SBR4) causes the glass transition temperature to increase by about 25 K.
DSC Measurements of Differently Vulcanized SBR Elastomers | Thermal Analysis Application No. HB444 | Application published in METTLER TOLEDO TA Application Handbook Elastomers, Volume 2