Factors Affecting TG Measurements

The difference between the actual temperature of a sample and the temperature indicated on TG recording paper is highly dependent on the geometrical relationship of the sample, furnace, and temperature sensor. If the sensor is not directly attached to the sample holder, the temperature indicated may be profoundly influenced by ambient conditions and heating rate in such instances, a temperature calibration is usually required. 

Some potential problems exist in determining accurately the sample weight in a TG apparatus because of the buoyancy effect. Thus, the aerodynamic forces of flow gas, the condensation of gaseous products on the cooler parts of the sample suspension system, and sample loss from the holder caused by an excessive gas flow rate may introduce errors in the determination of sample weight loss. 

The major factors that affect thermal analytical data are related to the shape, size, and weight of the sample. Samples are preferably in a powder or particle form, smaller than 0.1mm in diameter. If water or volatile solvents are present, the sample diameter should be smaller than 0.05 mm. However, an exceedingly small sample size may create a buoyancy effect and should be avoided. 

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