Chemical and physical properties generally depend on the temperature. Thermal analysis is a group of methods used in material sciences for investigation of such properties.
The most common properties and measurement methods are the following:
- Dimensions (length): dilatometry (DIL)
- Mechanical properties (stiffness, Young modulus, etc.): thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA)
- Mass: thermogravimetry (TGA)
- Temperature differences (for detection of phase transitions and chemical reactions): Differential thermal analysis (DTA) and differential scanning calorimetry (DSC)
- Mass and temperature differences: simultaneous thermal analysis (STA)
- Thermal diffusivity and thermal conductivity: laser flash analysis, heatflowmetry, hot wire technique
As almost every physical property is temperature dependent (electrical conductivity, Seebeck coefficient, optical and dielectrical properties etc.) all their investigations are part of thermal analysis.
Thermal analysis can be done in static or dynamic mode. In dynamic mode, temperature change is done either as a scan or in stepwise mode and the parameter is detected as a function of this temperature. In static mode, temperature remains constant and monitoring of a property is done over time. In static mode, often another parameter changes over time like gas pressure, gas composition, force etc.
Depending on the used thermal analysis technique a very broad range of materials can be tested. DSC (and DTA) is used for analysis of phase changes (solid-liquid and solid-solid) as well as for monitoring of chemical reactions (ageing, oxidation, decomposition etc.) in polymers, food, pharmaceutics but also for metals and ceramics.
Depending on the property to be analyzed, the methods are: Dilatometry (length change), TMA (mechanical properties), DTA and DSC (phase changes, chemical reactions, enthalpy determination), TGA (weight changes), STA (=TGA +DTA/DSC), LFA (thermal diffusivity /conductivity), HFM (thermal conductivity), THB (thermal conductivity), LSR (electric resistivity and Seebeck coefficient).
More detailed information about the techniques can be found in the dedicated chapters.