Lubricants
What is it?
Thermogravimetric Analysis (TGA) is a technique in which the mass of a substance is monitored as a function of temperature or time as the sample specimen is subjected to a controlled temperature program in a controlled atmosphere.
Why do we use it?
TGA is commonly used to determine selected characteristics of materials that exhibit either mass loss or gain due to decomposition, oxidation, or loss of volatiles (such as moisture).
For lubricants, TGA allows us to determine the weight loss characteristics of different base fluids or formulations resulting from evaporation, oxidation or thermal cracking.
How does it work?
The TGA instrument continuously weighs a sample as it is heated or maintained at a defined temperature. The sample is typically exposed to air or nitrogen atmosphere.
A plot of weight/mass against temperature or time produced by a thermogravimeter is called a Thermogram.
Typical Test Conditions:
There are three types of thermogravimetry:
- Dynamic TGA – where the sample is subjected to continuous increase in temperature (usually linearly) with time.
- Isothermal TGA – where the sample is maintained at a constant temperature for a period of time during which change in weight is recorded.
- Quasistatic TGA – where the sample is heated to a constant weight at each of a series of increasing temperature.