The Different Types of Thermal Analysis

 

Thermal analysis is the measurement of how specific physical or chemical properties of a substance changes with temperature. The early forms of thermal analysis were based mostly on Thermal Gravimetric Analysis where the change in weight of a substance with temperature was measured. This is probably, even now, the most common form of thermal analysis and will be discussed in more detail in this book. However, a number of other thermal analysis procedures have been introduced and will also be briefly discussed. The more important generally accepted thermal analytical techniques are listed as follows.

 

1/ Thermo-Gravimetric Analysis (TGA). The mass of a sample is monitored as a function of temperature

 

2/ Differential Thermal Analysis (DTA). The sample and an inert reference standard are heated through an identical temperature program and the temperature difference between the standard and the sample during the program recorded.

 

3/ Differential Scanning Calorimetry (DSC). The amount of heat required to raise the temperature of a sample and a standard are measured over a temperature cycle and the heat difference between that absorbed by the sample and reference are measured relative to their temperature.

 

4/ Thermo-Magnetometry  (TM ). The magnetic properties of the sample are measured as a function of temperature. Used to identify types of magnetization. Existing in different materials

 

5/ Dielectric Thermal Analysis (DTA). An alternating electric field is applied across the sample that may be held at a given temperature, the temperature programmed or the temperature merely monitored and the alternating current through the sample measured.  The technique is used to examine rheological changes in, for example, the processing of thermoplastics.

 

6/ Differential Mechanical Thermal Analysis (DMTA). This technique involves applying cyclic stresses to a sample that may be held at a given temperature, the temperature programmed or the temperature merely monitored and then removing the stress and observing the nature of the stress decay. The technique can be used for visco-elastic measurements, for example, the determination of the transition temperature of glass.

 

The list above covers most of the more common types of thermal analysis but there are other thermal analytical techniques, some of which are in the process of development at this time. Each of the above techniques will now be considered in some detail starting with the most widespread and popular technique, thermal gravimetric analysis.