What Is Thermogravimetric Analysis?

Thermogravimetric analysis, referred to as thermogravimetric analysis, is a method of measuring the relationship between the mass of a substance and temperature or time under a program-controlled temperature. The instrument for thermogravimetric analysis, called thermogravimetry, is mainly composed of three parts: temperature control system, detection system and recording system. The application of thermogravimetric analysis is mainly in the fields of metal alloys, geology, polymer materials research, and pharmaceutical research.

Thermogravimetric analysis is a method of measuring the relationship between the mass of a substance and temperature or time under a program-controlled temperature. By analyzing the thermogravimetric curve, we can know the composition, thermal stability, thermal decomposition, and products of the sample and its intermediate products, which are related to quality.

Derived from thermogravimetric analysis, we can derive derivative quotient thermogravimetric analysis, also called derivative thermogravimetric analysis, which is a technique for recording the first derivative of a TG curve against temperature or time. The result obtained by the experiment is the differential quotient thermogravimetric curve, that is, the DTG curve. The mass change rate is the ordinate, which decreases from top to bottom; the abscissa is temperature or time, and the increase from left to right.

The main feature of thermogravimetric analysis is that it is highly quantitative and can accurately measure the mass change and rate of change of a substance. Based on this feature, it can be said that as long as the mass of a substance changes when heated, it can be studied by thermogravimetric analysis. The figure shows the physical and chemical changes that can be detected by thermogravimetric analysis. We can see that these physical and chemical changes all have mass changes, such as sublimation, vaporization, adsorption, desorption, absorption, and gas-solid reaction. ^[1]

The results of thermogravimetric analysis are related to the experimental conditions. In order to obtain a thermogravimetric curve with good accuracy and repeatability, we must carefully analyze various factors. The factors that affect the results of thermogravimetric testing can basically be divided into three categories: instrument factors, experimental condition factors, and sample factors.

Instrument factors include gas buoyancy and convection, crucibles, volatiles condensation, balance sensitivity, sample holders, and thermocouples. For a given thermogravimetric instrument, the effects of balance sensitivity, sample holder, and thermocouple are fixed. We can reduce or eliminate these system errors through mass and temperature corrections ^[2]

The application of thermogravimetric analysis is mainly in the fields of metal alloys, geology, polymer materials research, and pharmaceutical research.

Thermogravimetric determination of metal-gas reaction

The reaction between metal and gas is a gas-solid phase reaction. Thermogravimetric analysis can be used to determine the relationship between the mass change and temperature of the reaction process, and it can be used for the kinetic analysis of the reaction amount.

Application of thermogravimetric analysis in geology

Mineral identification: Thermogravimetric curves of minerals will show different characteristics due to their different composition and structure. Minerals can be identified by comparing the starting temperature, peak temperature, and peak area with known mineral characteristic curves.

Thermogravimetric analysis

The quality of the sample changes under the control of the program temperature, and this phenomenon can be used to quantitatively analyze the components of the sample. Compared with general chemical analysis methods and other methods, thermogravimetric analysis has the unique advantages of quantitative analysis of samples, that is, the sample does not require pretreatment, the analysis does not require reagents, and the operation and data processing are simple and convenient. The only requirement is that the two mass loss processes adjacent to the thermogravimetric curve must form an obvious platform, and the more obvious the platform, the smaller the calculation error.

Application of thermogravimetric analysis in polymer materials

Thermal stability of materials: Thermogravimetric analysis can evaluate the thermal properties of polyolefins, polyhaloolefins, oxygen-containing polymers, aromatic heterocyclic polymers, monomers, polymers and polymers, and elastomeric polymers. Stability ^[3] .