Category Archives: TGA

thermal gravimetric analysis

Measurement Modes in Thermogravimetric Analysis (TGA)

TGA analysis is a technique that measures sample weight change in-situ with temperature.  There are two frequently used modes in TGA.  One is constant heating rate and the other is isothermal temperature hold.

When an analyst is looking for an overall survey of how a sample behaves as temperature increases, such as temperature regions relating to volatiles or sublimation or degradation, a constant heating rate is applied in TGA testing.  On the other hand, the isothermal temperature hold is utilized for moisture or volatile content analysis.  A sample is heated to a temperature slightly higher than the boiling point of the volatile compound and held for some time until sample weight becomes stable.  This mode is similar to drying a sample in an oven.

Sometimes a more complex measurement mode is needed to improve resolution after a survey scan of constant heating rate.  The TGA method may apply variable heating rates and/or isothermal steps in order to distinguish each weight loss step more clearly.  Techniques to achieve better resolution include high resolution (“hi-res”) TGA, modulated TGA, or constant rate of weight change methodology.

TGA Analysis for Quality Assurance

Thermal gravimetric analysis (TGA) is a technique that measures the sample mass as a function of temperature. Imagine that you put a sample on a balance and track its weight as it is heated in an oven. By tracking the sample mass you can observe if there is any weight loss or weight gain during heating. And the weight loss or weight gain you observe from a TGA test can usually be correlated to some aspect of the sample.

TGA analysis is useful in measuring residual solvent content and percent solids. In some instances, TGA analysis is adapted for quality assurance, which replaces other analytical methods such as drying samples in an oven and quantitative GC analysis of solvents.

There are many products made in solutions. While in solution, the solids content is controlled so that the manufacturing process can be executed as desired. TGA analysis has been used here to measure the percent solids content of the solution. At the end of manufacturing process, solvents are removed from the finishing products. The residual solvent content in a product can also be verified by TGA analysis.

TGA analysis is also useful in applications where very low volatile content is expected of a material. For example, in semiconductor industry and in solar panel industry where outgassing may interfere with product performance, material selection is chosen so that minimal weight loss occurs during product life. In this case, TGA analysis has been used to screen samples for material selection during product development and it is adapted for quality control during material manufacturing.