Thermomechanical analysis (TMA) determines dimensional changes of solids, liquids or pasty materials as a function of temperature and/or time under a defined mechanical force (DIN 51 005, ASTM E 831, ASTM D 696, ASTM D 3386, ISO 11359 – Parts 1 to 3).
TMA is closely related to dilatometry. The difference is the force/load which is applied to the sample. Dilatometry works with a negligible load, TMA with a fixed (free selectable) force. In both cases, the change in sample dimension (length change) is measured as a function of temperature or time.
Many materials undergo changes of their thermomechanical properties during heating or cooling. For example, phase changes, sintering steps or softening can occur in addition to thermal expansion. TMA analyses can hereby provide valuable insight into the composition, structure, production conditions or application possibilities for various materials.The application range of instruments for thermomechanical analysis extends from quality control to research and development. Typical domains include plastics and elastomers, paints and dyes, composite materials, adhesives, films and fibers, ceramics, glass and metals.
Irrespective of the selected type of deformation (expansion, compression, penetration, tension or bending), every length change in the sample is communicated to a highly sensitive inductive displacement transducer (LVDT) via a push rod and transformed into a digital signal. The push rod and corresponding sample holders of fused silica or aluminum oxide can be quickly and easily interchanged to optimize the system to the respective application.
- Linear thermal expansion
- Coefficient of thermal expansion
- Phase transition temperatures
- Sintering temperatures
- Shrinkage steps
- Glass transition temperatures
- Dilatometric softening points
- Volumetric expansion
- Decomposition temperature, e.g. of organic binder
- Caloric effects
- Density changes
- Sintering kinetics
This chart shows the thermal expansion (dL/Lo = relative length change) and the resulting curve of the coefficient of expansion (T. Alpha) of sapphire compared to literary data (circles). The result demonstrates the high accuracy which can be achieved with the TMA 402 Hyperion®.