Thermogravimetric Analyzer (TGA) - A329
| Thermogravimetric Analyzer (TGA) | |
|---|---|
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| Thermogravimetric Analyzer, TA Instruments, Discovery 5500 | |
| Document Type | Article |
| Document Identifier | 329 |
| Themes | |
| Relevant Class |
Equipment |
| Tags | |
| Factory Cells | |
Introduction[edit | edit source]
Thermogravimetric Analysis (TGA) is a method that monitors the mass of a sample as the temperature is varied. It can be used to determine the fraction of volatiles and the thermal stability of a material.[1][2] Mass is monitored as a function of temperature or time in a controlled temperature and atmosphere program.[1]
The TGA instrument can heat samples up to temperatures of around 1200°C, depending on the make and model. It can also cool samples to around -40°C by using nitrogen fed into the chamber, which may vary on make and model of equipment. The typical sample size is between 2 and 50 mg.[1]
Features[edit | edit source]
The TGA consists of a sample pan, which is supported by a highly precise scale, and a furnace chamber that can be heated or cooled during the experiment. The mass of the sample is carefully monitored and logged during the temperature changes. The environment of the chamber is controlled by injecting a gas into the chamber during the experiment, the gas may be reactive, like air or oxygen, or inert, like argon or helium, depending on the desired outcomes of the test.[1][2][3]
Uses and Test Types[edit | edit source]
The TGA instruments can be used for polymers to quantify loss of water, solvent and other volatiles as well as characterizing pyrolysis, decomposition and oxidation to name a few.[1] Mass loss due to volatiles such as moisture or residual solvents occurs in general between ambient and 300°C. Reaction products generally happen between 100°C and 250°C, forming products such as water and formaldehyde. Degradation tends to occur between temperatures of 200°C and 800°C.[3]
There are three variations of tests generally performed in a TGA instrument. Firstly, a constant temperature increase from a specified temperature to a target temperature. This will show the temperature ranges at which gases are removed from the sample and the onset of thermal degradation. Secondly, a static test, where the temperature is held at a certain setpoint. This is usually used to monitor degradation over time at a specified temperature. Lastly, a stepwise increase in the temperature, where a sample is held at certain temperatures until the mass is stabilized. This may be used to monitor how decomposition occurs.[3]
Analysis of Results[edit | edit source]
A typical TGA graph consist of the mass or percentage change in mass on the y-axis and the temperature or time on the x-axis. We can then see a drop in the mass at certain temperature ranges, indicating that a change in the compound has happened[1]. The graph can be used do determine how much of a certain component has been lost and what remains. For example the graph shown here displays the degradation of a polystyrene sample during a ramp of 4°C/min up to 500°C.
By using the first derivative of the TGA curve (DTG), it becomes clearer where there are events taking place in the mass loss curve and may aid in separating out different processes taking place.[3] This is through the DTG curve providing local maxima to indicate areas of maximum mass loss. In the example shown, the derivative curve clearly shows the temperature range where the maximum weight loss occurs and can assist in indicating where the weight loss is starting to occur.
Combining Instruments[edit | edit source]
The TGA gives information on the temperatures and times the mass of a sample changes, however it does not indicate the types of substances that are coming off the sample. A TGA may be combined with other instruments that can analyze the gasses coming off in a process usually referred to as evolved gas analysis (EGA). This is where the off gasses are transferred out of the TGA into a separate piece of equipment, usually a Fourier transform infrared spectroscopy (FTIR) or a mass spectroscopy (MS) device.[4] A TGA may also be combined with a differential scanning calorimeter (DSC) in order to provide energetic information of the sample as it proceeds through the temperature ramp. This will provide information on the enthalpy changes occurring and detect changes and reactions not apparent through mass observations. All these combinations are used to prevent ambiguities when performing tests on different samples, temperatures and atmospheric conditions, by simply performing all of the analyses at once.[3]
Related pages
| Page type | Links |
|---|---|
| Introduction to Composites Articles | |
| Foundational Knowledge Articles | |
| Foundational Knowledge Method Documents | |
| Foundational Knowledge Worked Examples | |
| Systems Knowledge Articles | |
| Systems Knowledge Method Documents | |
| Systems Knowledge Worked Examples | |
| Systems Catalogue Articles | |
| Systems Catalogue Objects – Material | |
| Systems Catalogue Objects – Shape | |
| Systems Catalogue Objects – Tooling and consumables | |
| Systems Catalogue Objects – Equipment | |
| Practice Documents | |
| Case Studies | |
| Perspectives Articles |
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 [Ref] PerkinElmer (2015), A Beginner's Guide Thermogravimetric Analysis (TGA) FAQ (PDF), PerkinElmer, retrieved 20 July 2022CS1 maint: uses authors parameter (link) CS1 maint: date and year (link)
- ↑ 2.0 2.1 [Ref] Rajisha, K.R. et al. (2011). "Thermomechanical and spectroscopic characterization of natural fibre composites". Woodhead Publishing. doi:10.1533/9780857092281.2.241. Cite journal requires
|journal=(help);|access-date=requires|url=(help)CS1 maint: extra punctuation (link) CS1 maint: uses authors parameter (link) - ↑ 3.0 3.1 3.2 3.3 3.4 [Ref] Menczel, Joseph D.; Prime, R. Bruce (2009). Thermal Analysis of Polymers: Fundamentals and Applications. John Wiley & Sons, Inc.CS1 maint: uses authors parameter (link) CS1 maint: date and year (link)
- ↑ [Ref] Redshift (2019). [_What_is?_What_Instruments_to_Use?_What_Can_You_Achieve? "Evolved Gas Analysis (EGA), What is? What Instruments to Use? What Can You Achieve?"] Check
|url=value (help) (published June 2019). Retrieved 21 July 2022.CS1 maint: uses authors parameter (link) CS1 maint: date and year (link)
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