The oil added to the elastomer as a plasticizer often vaporizes at temperatures at which the pyrolysis of the polymer begins. The influence of reduced pressure on the TGA curve is demonstrated using SBR as an example.
Sample A; solution-polymerized SBR
Sample B: same as sample A, but containing oil
Measuring cell: TGA/SDTA851e
Pan: Alumina 30 μl
Sample preparation: Piece of elastomer of approx. 15 mg
TGA measurement: After inserting the sample at 50 °C, the pressure was reduced to 10 mbar over a period of 10 minutes. The balance protection gas flow was 20 Nml/min of nitrogen. Heating from 50 °C to 550 °C at 10 K/min
Atmosphere: Partial vacuum
The use of vacuum resulted in a good separation of the vaporization process o B B f the oil and the pyrolysis of the SBR. The DTG curve of sample A shows that a minor process with a mass loss of a few percent occurs prior to the pyrolysis peak. In sample B, this effect is overlapped by the vaporization of the oil.
The separation of vaporization and pyrolysis processes can be greatly improved by performing TGA measurements at reduced pressure.
TGA of SBR With and Without Oil at Reduced Pressure (Vacuum) | Thermal Analysis Handbook No.HB481 | Application published in METTLER TOLEDO TA Application Handbook Elastomers Volume 2