Thermogravimetric Analysis (TGA)
Formulation Testing
Significance and Test Method
Elastomers and thermoplastic elastomers are mixtures of numerous ingredients. In addition to rubber, they contain additives, processing aids, plasticisers, curing agents, fillers and reinforcing materials. Both the components themselves and their content in the elastomer compound influence the subsequent performance characteristics of the components.
With the help of a thermogravimetric analysis (TGA), the composition of an elastomer formula can be described within certain limits and the contents of the main ingredients can be measured quickly and repeatably.
The evaluation of a formula by means of TGA allows the quantitative determination of the mixture ingredients, divided into
- vaporisable or volatile substances (mainly plasticisers)
- pyrolysable substances (mainly polymer or rubber)
- oxidisable substances (mainly carbon black) and
- non-oxidisable substances, also referred to as ash residue (fillers, especially metal oxides)
Significance of the TGA for Application Technology
The TGA is a helpful method for checking the composition of a rubber material as part of initial sampling and, in case of doubt, for series monitoring. TGA also provides valuable information for damage analyses and often allows important conclusions to be drawn.
Testing by means of TGA
There are various standards and test specifications that describe definitions and tests for determining the composition of polymers by means of TGA. These include DIN EN ISO 11358, ISO 9924 or VDA 675 135.
During the test, a material sample of approx. 10 mg is continuously heated up to a maximum of 1000 °C and the relative weight loss of the material over the temperature is determined and shown as a graph in a chart. During heating, the vaporisable components first dissolve from the material until a sudden decomposition of the polymer (= pyrolysis) takes place. Afterwards, the oxidised elements can then provide information about the content of black carbon. What remains is the ash residue.
The obtained TGA curve is characteristic for an elastomer formulation.
Downloads
Find more information on physical analysis and thermogravimetric analysis in our technical reports:
Physical and analytical test methods
In this report, the authors Bernd Sprenger, Dipl.-Ing. Bernhard Richter and Dipl.-Ing. (FH) Ulrich Blobner present the three most important methods of physical analysis for elastomers. They explain the methods of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA).
