To demonstrate the influence of plasticizers on the glass transition temperature measured by DSC, using SBR and an oil as an example.
Solution-polymerized SBR:
Without oil: (VSL 5025-0)
With 37.5% oil: (VSL 5025-1)
Measuring cell: DSC822e with liquid nitrogen cooling option
Pan: Aluminum standard 40 ul, pierced lid
Sample preparation: Pieces of elastomer of approx. 10 mg
DSC measurement: The samples were cooled to –90 °C at 5 K/min and then measured. Heating from 90 °C to 30 °C at 10 K/min
Atmosphere: Nitrogen
The glass transition temperature of the sample without oil is –19.8 °C. With 37.5% oil, the glass transition temperature decreases to –25.6 °C. The height of the glass transition step, 'cp, is approx. 0.42 J/(gK) and remains unchanged.
Oil acts as a plasticizer and shifts the glass transition to lower temperatures. In the example analyzed, addition of oil to the elastomer lowers the glass transition temperature by about 6 K.
DSC Measurements of the Plasticization of SBR | Thermal Analysis Application No. HB 483 | Application published in METTLER TOLEDO TA Application Handbook Elastomers Volume 2