DSC Measurements of Differently Vulcanized SBR Elastomers

Purpose

The measurement of differently vulcanized SBR samples by DSC 

Sample

The samples are described in Section 4.2.2.

Conditions

Measuring cell: DSC822^e 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

Evaluation

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. 

Conclusions

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}