termogravimetric

Thermogravimetric analysis (TGA), sometimes spelled termogravimetric analysis, is a thermal analysis technique that measures a sample's mass as a function of temperature or time under a controlled atmosphere. It is used to study composition and thermal stability, including moisture content, solvent loss, decomposition, oxidation, and ash formation.

Principle and instrumentation: A small sample is placed in a pan on a precision balance inside a furnace. The balance continuously records mass while the temperature is programmed or held constant in a chosen gas environment, such as nitrogen, air, or synthetic air. The resulting thermogravimetric (TG) curve shows mass loss versus temperature or time, and the derivative curve (DTG) highlights the rate of mass loss.

Operation and data interpretation: Typical experiments employ heating rates from about 0.5 to 40 C per minute and may be dynamic or isothermal. Weight losses indicate processes such as moisture volatilization, solvent removal, polymer decomposition, oxidation, or ash formation. The DTG curve helps resolve overlapping steps. In kinetic studies, TGA data can be used to estimate parameters like activation energy using methods such as Kissinger or Flynn–Wall–Ozawa.

Applications: TGA is widely used in polymer science, materials characterization, catalysis, pharmaceuticals, and energy materials to assess thermal stability, composition (e.g., filler loading or moisture content), and mass changes during heating or decomposition. It often serves as a complementary technique alongside differential scanning calorimetry (DSC) and evolved gas analysis methods (e.g., FTIR, MS) for identifying volatile products.

Limitations and notes: Accurate interpretation requires representative sampling and careful calibration. Gas atmosphere and sample interactions can influence results, and very volatile products may complicate analysis.