Modern thermal analysis often refers to a process known as TGA. It stands for thermogravimetric analysis and is used to measure the weight of a material after it’s exposed to heat. However, it’s more than a simple solids check (done by burning off flammable materials to see what is left). Here is more about the process and some of its applications.
Weight Changes
TGA can be determined by increasing the temperature of a substance or by using and isothermal comparison. Isothermal means that certain properties of a material are measured as the temperature stays constant. Isothermal testing is usually done in a vacuum with a gas like nitrogen or helium. In some cases, a mass spectrometer is also used for measuring vapors, but the two processes may be used separately for more accurate results.
What Materials Are Measured with TGA?
Many kinds of polymers, metals, glass, ceramics, composite, and manmade materials may be checked with this thermal analysis method. Testing temperatures can vary a great deal. For example, some tests are run at temperatures as low as 77 degrees Fahrenheit (25C) and as high as 2732 degrees Fahrenheit (1500C).
The weight of materials may be as low as one milligram. However, most tests work best with materials at least ten milligrams in weight and can be as heavy as 150 milligrams with a weight variance in the test as little as .01 milligram. For best results, the testing material is usually cut into small pieces or turned into a powder.
Applications
Thermal analysis may be used to determine the moisture content of some materials. Some tests reveal how a substance reacts to the atmosphere or specific gasses. Rates of evaporation can be measured with TGA. It’s also a good way to determine the composition of plastics. In some cases, you can tell how much filler material has been used in a substance.
