Thermogravimetric analysis (TGA) is a method of thermal analysis that measures weight changes in a material as a function of temperature (with constant heating rate), or as a function of time (with constant temperature) in a controlled atmosphere.
How it works. A TGA consists of a sample pan that is supported by a precision balance. That pan resides in a furnace and is heated or cooled during the test. The weight of the sample is monitored during the experiment. The changes in the weight are related to the changes in the material chemical or physical properties and can be detected to a fraction of a microgram. Thermal gravimetric analyzer can be interfaced with a mass spectrometer (TGA/MS) or FTIR to identify and quantitate the volatile and pyrolysis products generated due to changes in the material chemical properties (decomposition).
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Instrumentation Available
Key Attributes
- Sample Weight: 1 mg to 150 mg;
- Temperature Range: Ambient to 1000°C;
- Atmosphere: Nitrogen, Oxygen, Helium;
- Controlled Heating Rate: 0.01 to 100°C/minute;
- Weight change sensitivity of 0.01 mg.
Strengths
- Samples can be analyzed in the solid (powder or small pieces) form or liquid form;
- Small sample size;
- Qualitative or quantitative analysis of inorganic or organic materials;
- Detection of multiple mass loss thermal events from physical and chemical changes of materials.
Limitations
- Initial sample weight must be stable;
- The maximum furnace temperature is 1000°C;
- MS or FTIR coupled with the TGA are required for a quantitative analysis of the material composition.
Applications
- Determines temperature and weight change of decomposition reactions, which often allows quantitative composition analysis;
- May be used to determine water content or the residual solvents in a material;
- Can be used to measure evaporation rates as a function of temperature, such as to measure the volatile emissions of liquid mixtures;
- Helps to identify plastics and organic materials by measuring the temperature of bond scissions in inert atmospheres or of oxidation in air;
- Used to measure the weight of fiberglass and inorganic fill materials in plastics, laminates, paints, primers, and composite materials by burning off the polymer resin;
- Can measure silica gels, cellulose, calcium carbonate, and titanium dioxide;
- Can determine the purity of a mineral, inorganic compound, or organic material;
- Distinguishes different mineral compositions from broad mineral types, such as borax, boric acid, and silica gels.
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