What does thermogravimetric analysis (TGA) measure?

The development of new materials and their quality analysis are the most important pillars for adding value to a product and differentiating it in the market. For this, it is essential to carry out quality tests that allow us to ensure that everything is correct. The physical-chemical characterization tests, which provide us with information on the behaviour of materials when subjected to different environmental conditions.

At ATRIA, we perform TGA analysis to study the thermal stability and composition of materials. This technique helps to understand how a material behaves when exposed to temperature changes and to detect mass loss due to decomposition or volatilization. If you need to accurately characterize your materials, contact us!

In this blog we are going to explain in detail one of the most interesting physical-chemical characterization tests that we use in our projects: the Thermogravimetric Analysis known as TGA.

How does the TGA thermogravimetric analysis equipment work?

In TGA thermogravimetric analysis, the mass variation of a material is studied when it is subjected to a controlled process of temperature increase. For this purpose, the TGA equipment consists of a precision balance on which the sample is weighed continuously while it is heated in the presence of an oxidizing gas or an inert gas.

Many solids, when heated, undergo reactions that generate gaseous by-products. In TGA, these gaseous by-products are removed and changes in the remaining mass of the sample are recorded. Three variations are commonly employed:

• Dynamic TGA: temperature increases with time as mass is recorded. Its main application is to assess how matter behaves with increasing temperature and to analyze different components that have different temperature resistance.
• Static TGA: the temperature is kept constant while the mass is measured. Its main use is to analyze a decomposition occurring at a given temperature or to study the resistance of a material at a given temperature.
• Quasi-static TGA: the sample is heated at successive temperature intervals, with alternating isothermal stages until stabilization of the sample mass occurs. This test is used to evaluate possible decomposition products and to better characterize how they decompose at different temperatures.

How is a TGA thermogravimetric analysis measurement performed?

To carry out a thermogravimetric analysis measurement, the first step is to take a sample of the material to be analyzed. In case we want to analyze the behaviour of the volatile compounds that compose the sample, it is necessary that the mass of the sample is stable at room temperature. If the objective of our analysis is to evaluate the state of the sample at high temperatures, the volatile components will not be taken into account.

After that, it is necessary to define a temperature program that suits our needs. For example, if our objective is to evaluate the temperature of elimination of volatile compounds from a paint, it will be important to set a temperature increase rate that is not too high in order to observe the mass variations more accurately. On the other hand, if our objective is to evaluate the amount of inorganic additive in a polymeric sample, our focus will be on reaching a temperature high enough to completely eliminate the organic component of the sample.

What is a TGA thermogravimetric analysis for?

As we have indicated above, thermogravimetric analysis is a powerful tool for sample analysis, from the point of view of the development of a new material, as well as from the point of view of analyzing the quality of a product and analyzing its possible defects. Therefore, it is important to point out the different applications of this type of analysis:

• Evaluate the decomposition temperature of a material. This is one of the most common uses as it allows us to define the resistance of the material with the temperature increases it may experience. This information provides us with information on the quality of a product or on its thermogravimetric profile for complementary tests.
• Evaluate phase changes and thermal resistance of the components of our sample. Another widely studied use of thermogravimetric analysis is to subject the sample to temperature ramps with small temperature increase ratios to evaluate the state of the sample at different temperatures.
• Evaluate the presence of inorganic components. One of the most important uses when we want to know the percentage of inorganic matter in a material is to perform a thermogravimetric test. To do this, we will define a temperature program that will allow us to decompose all the organic matter, making sure that the measurement of the residual mass that we obtain corresponds only to the inorganic components such as additives or pigments, among others.
• Evaluate the presence of different organic components. In this case, as long as we have organic components with different thermal decomposition temperatures, we will be able to differentiate and quantify the amounts of different compounds that make up our sample.

TGA Thermogravimetric Analysis Applications

Thermogravimetric analysis is widely used in materials analysis laboratories. Therefore, its applications can be found in a wide range of industrial and scientific research. Here are some of the most interesting applications:

• Thermal resistance of a thermoplastic that makes up a material that reaches high temperatures. In this case, the customer presented us with the problem of one of its products. Prior to the appearance of the defect, the raw material was changed in the manufacture of the product and thermogravimetric analysis showed that its degradation occurred at lower temperatures than the product model used previously.
• Development of new polymeric materials. In this case, thermogravimetric analysis is presented as a quality tool complementary to other tests, since the amount of inorganic additive added and its correlation with resistance to different laboratory tests were observed.
• Analysis of the behaviour of a paint during its application. In this particular case, thermogravimetric analysis was used as a fundamental tool in understanding the curing process of a paint. Through it, it was possible to evaluate how the phase of the paint changed and at what temperature the most volatile compounds evaporated. Finally, it was possible to differentiate the polymeric organic compounds that gave consistency to the paint, as well as their degradation temperature.

Advantages and limitations of TGA thermogravimetric analysis

The main advantages of thermogravimetric analysis are:

• High reliability of the results, since it consists of a balance with high precision to detect mass changes.
• Wide variety of uses thanks to the easy definition of temperature programs.
• Can be coupled with other techniques, resulting in combined information such as FTIR or GC-MS.

The main disadvantages of thermogravimetric analysis are:

• Only mass changes in the sample are analyzed, it is not possible to analyze crystalline phase changes.
• It does not allow differentiation between materials with the same thermal decomposition temperature.
• It is necessary to have experience in the interpretation of the signals obtained.

Our TGA Thermogravimetric Analysis Service

At ATRIA, TGA thermogravimetric analysis is one of the quality tools used par excellence. As we have explained in the post, due to its wide range of applications, we integrate it in all those cases of study where we have to evaluate the correct development of a material, evaluate the quality of final products or as a link in the chain of characterizations that allow us to apply the so-called forensic engineering to define and solve production failures.

Therefore, we encourage you to contact us whenever you need to know more information about your product, regardless of its stage of development.

Do you want to perform thermogravimetric analysis on one of your projects? Contact us!