A thermal analysis method that records sample mass change as a function of temperature or time under controlled atmosphere and heating program to study decomposition, desorption, oxidation, and compositional stability.

Principle

Mass change measured by a microbalance while the sample is heated or held is interpreted as loss or gain of volatile components, decomposition of chemical structures, or reaction with the atmosphere; variation of heating rate, atmosphere and sample mass affects observed profiles and kinetics.

Demonstration

Heat a polymer sample under nitrogen from room temperature to 800 °C and observe weight-loss steps corresponding to moisture desorption, side-chain cleavage, main-chain decomposition, and final inorganic residue; use derivative thermogravimetry (DTG) to locate maximum rates; change to oxygen to reveal oxidative mass gains/losses.

Misapplication

Assigning specific decomposition chemistries to mass-loss steps without complementary evolved-gas analysis, ignoring buoyancy and balance drift corrections, using inappropriate heating rates or sample sizes that alter apparent onset temperatures and kinetics.

Consequence

Provides thermal stability profiles, decomposition onset temperatures, estimates of volatile content or filler fraction, and guidance on processing windows and shelf life when performed with controlled conditions and interpreted cautiously.

Reversal

Differential scanning calorimetry reports heat-flow events rather than mass change and can detect transitions that do not involve mass loss; coupling TGA with mass spectrometry or FTIR (evolved-gas analysis) inverts the problem by identifying volatiles rather than only quantifying mass change.

Boundary

Reports only mass versus time/temperature and thus does not identify the chemical identity of evolved gases; results are sensitive to heating program, atmosphere, sample geometry and instrument calibration; quantitation in complex mixtures requires standards or complementary techniques.

Semantic Tension

Tension between TGA and calorimetric methods (mass vs heat) and between standalone TGA interpretation and coupled evolved-gas methods — mass profiles are informative but ambiguous without species identification.

Synthesis

Thermogravimetric analysis monitors mass as temperature or time changes under controlled atmosphere to reveal thermal events and stability; it is a powerful indicator of composition and decomposition behavior but typically requires complementary analyses to assign chemical mechanisms confidently.