Termogravimetry

Termogravimetry, also known as thermogravimetry or thermogravimetric analysis (TGA), is a thermal analysis technique in which the mass of a sample is measured continuously as a function of temperature or time under controlled heating or cooling. The technique detects changes in mass caused by processes such as water loss, solvent evaporation, decomposition, oxidation, or carbonization, allowing analysis of composition, thermal stability, and kinetics.

An instrument typically consists of a microbalance enclosed in a furnace with a controlled atmosphere, connected to a computer. Small samples (often milligrams) are weighed and heated according to a programmed temperature ramp or held at a fixed temperature. The atmosphere can be air, inert gases (nitrogen, argon), or reactive gases, affecting the observed reactions.

In dynamic TGA, weight is recorded during a continuous temperature ramp, producing a mass versus temperature curve. The derivative of mass with respect to temperature (DTG) highlights stages of rapid mass loss. Isothermal TGA holds the sample at a fixed temperature to study decomposition or desorption over time.

Applications include determination of moisture or volatile content, ash yield, polymer degradation temperatures, kinetics of decomposition, studying filler content in composites, catalyst supports, and calculation of char yield. Data interpretation may involve kinetic models (e.g., Kissinger, Flynn–Wall–Ozawa), baseline corrections, and careful consideration of sample homogeneity and atmosphere effects.

Limitations include overlapping mass loss events, sensitivity to heating rate, and potential artifacts from oxidation. Overall, TGA provides quantitative insight into the thermal behavior and composition of materials.