Interpretation of TGA Data
Thermogravimetric analysis produces a curve, that shows the effect of temperature (or time), presented on the x axis, on the weight of the sample (the y axis). The weight is usually expressed
in terms of the percentage of the sample that remains, versus the weight at the start of the experiment, at a given temperature/time.
Our reports also include a second y axis on the
graph which presents the data for the first derivative of the TGA curve. This is known as the Derivative Thermogravimetric (DTG) curve and represents the rate of change of mass with respect to
temperature (e.g. % mass loss per degree Celcius) or time (e.g. % mass loss per second). The DTG curve often allows for easier visual interpretation of the data, as periods of large mass change
can be seen with more clarity.
The losses in mass at given ranges of temperature ranges can be said to provide indications with regards to the relative abundance of various chemical components in the sample.
For example, hemicelluloses degrade between 250 and 300 °C, whilst cellulose is known to rapidly become volatile under a relatively small temperature range of 300-325 °C under an air environment. These
temperature ranges tend to shift upwards when nitrogen is instead used as the environmental gas whislt the resolution of the analysis often improves when this gas is used.
A rapid drop in weight is usually indicative of an abundance of a particular component, whilst a
slow descline in weight can suggest the presence of multiple volatile components in the region.