Buyer’s Guide: Thermal Analysis Instrumentation

By Anne Arnold, Science Writer

Thermal analysis is a crucial technique utilized across various industries, offering vital insights that govern the applications of materials. By characterizing the thermal properties of materials, this analytical method enables industries to make informed decisions regarding material selection, process optimization, and product development. Serving as a cornerstone in research, quality control, and innovation, thermal analysis drives advancements and ensures the efficiency, reliability, and safety of products and processes in diverse industrial sectors such as oil and gas, aerospace, energy storage, pharmaceuticals, and more.¹

When selecting a thermal analysis instrument, key factors for consideration include the thermal properties to be analyzed, sample compatibility, technical specifications, and budgetary constraints. Given these considerations, this guide aims to provide buyers with the knowledge necessary to navigate purchasing decisions regarding thermal analysis instrumentation effectively.

Types of Thermal Analysis Instruments

Thermal analyzers encompass a family of analytical techniques, each uniquely designed to study the thermal properties of a material. Understanding the thermal properties you aim to investigate is necessary in selecting the most suitable thermal analyzer for your research or application needs. Here we will explore each type of thermal analyzer, detailing the thermal properties it measures and the critical understanding it offers about the material under investigation.

• Differential Scanning Calorimetry (DSC) measures the heat flow into or out of a sample as it undergoes physical or chemical changes. This technique measures phase transitions, enthalpy changes, and the heat capacity of materials.

• Thermogravimetric Analysis (TGA) determines how the weight of a material changes as a function of temperature, providing insight into thermal stability and decomposition behavior. Specifically, TGA provides a fundamental understanding of the decomposition kinetics, thermal stability, and moisture content of various substances.

• Differential Thermal Analysis (DTA) is an analytical approach that is similar to DSC; however, DTA measures the temperature difference between a sample and a reference material as a function of temperature (rather than heat in the case of DSC). This approach enables the determination of temperatures associated with phase and chemical transitions as well as enthalpy changes of materials.

• Dynamic Mechanical Analysis (DMA) is perhaps the most unique thermal method described, assessing the mechanical properties of materials in response to varying temperatures. This method offers insights into the modulus, damping, creep, and stress relaxation of materials as a function of temperature, along with providing complementary information such as a material’s glass transition temperature.²

Sample Compatibility Considerations for Thermal Analysis Instruments   

Thermal analysis techniques provide complementary information that enhances our understanding of material behavior. While techniques such as DSC, TGA, DTA, and DMA can test a wide range of sample types including solids, liquids, powders, and thin films, special attachments may be necessary to conduct the analysis accurately.

In the case of DSC, most sample types can be accommodated in a standard DSC pan, which is hermetically sealed to maintain a controlled environment. However, when analyzing liquid samples, special pans equipped with vents may be necessary to prevent pressure buildup or splattering. Similarly, TGA and DTA typically utilize standard pans suitable for a wide range of sample types. When analyzing liquids in TGA or DTA, special crucibles may be required, such as pans that contain lids to prevent evaporation during testing.

DMA necessitates more specific attachments depending on the sample type. For instance, solid and thin film samples require specialized grips or fixtures, with different fixtures designed for compressive, shear, or tensile testing. While solids and thin films can be analyzed in compression, shear, and tensile testing modes, liquids and powders are typically limited to compression and shear testing due to their physical properties.³

Key Technical Specifications to Consider When Choosing a Thermal Analyzer

The technical specifications of a thermal analysis instrument play a crucial role in determining its utility and the quality of data it provides. These instrument specifications include the temperature range, gas compatibility, resolution, software features, automation capabilities, and modularity. Each specification influences the instrument's performance and suitability for specific analytical needs. Therefore, understanding and carefully considering these key technical specifications is essential when choosing a thermal analyzer.

• Temperature Range: Selecting the appropriate temperature range for the instrument's oven is key for capturing the thermal transitions of interest in a material. DSC instruments typically offer a range from -180 °C to 725 °C, while TGA instruments commonly span from room temperature to 1000°C or higher. DTA instruments offer a similar range to DSC. DMA instruments operate within a range of -150 - 600 °C or higher.

• Gas Compatibility: The types of gases an instrument is compatible with are a vital consideration because they allow for control over the sample environment, which can be matched to real-world conditions. DSC, TGA, and DTA instruments generally operate with inert gases such as helium, nitrogen, or argon. However, they can also be set up to operate in air, carbon dioxide, or mixtures of gases. The choice of gas depends on its compatibility with the material of the oven. In contrast, DMA instruments are typically utilized using inert or air environments.

• Resolution: The temperature resolution significantly impacts the quality of results obtained from thermal analysis instruments. However, it is essential to consider several measurement parameters exclusive to each instrument concerning resolution. For example, DSC relies on resolution in temperature and heat flow, TGA on temperature and sample weight, DTA on temperature, and DMA on temperature and force. Careful consideration of these parameters ensures accurate and reliable measurements.

• Software Features: The software associated with thermal analysis instruments is an important factor, as it affords tools for data analysis, curve fitting, and kinetic investigation. Users may require data analysis tools tailored to their research or industrial needs, along with advanced functionalities for curve fitting and kinetic analysis. The software capabilities play a fundamental role in interpreting experimental data, extracting meaningful insights, and making informed decisions about material properties and behavior.

• Automation Capabilities: Considering whether an instrument is amenable to automation is also an important purchasing consideration, especially if high-throughput sample analysis is required. Most DSC, TGA, and DTA instruments can be adapted with autosamplers that load and unload sample pans into the oven for analysis based on a programmed sequence. DMA is more challenging to automate due to the loading requirements of a sample into a grip or fixture.

• Modularity: Modularity may be a technical specification of interest as it allows for the seamless integration of evolved gas analysis systems like Mass Spectrometry (MS) or Fourier Transform Infrared Spectroscopy (FTIR). This capability enables simultaneous measurement of thermal transitions and chemical composition of evolved gases, offering valuable insights into material decomposition and chemical reactions.

About the Author

Anne Arnold is a devoted Ph.D. materials chemist at Carnegie Mellon University, specializing in innovative materials for applications like tissue regeneration, 3D printing, sensors, and environmental remediation. With expertise in polymers, nanomaterials, and composites, she tackles complex challenges with creative solutions.

References

1. Handbook of Thermal Analysis and Calorimetry, Volume 6 - 2nd Edition | Elsevier Shop. https://shop.elsevier.com/books/handbook-of-thermal-analysis-and-calorimetry/vyazovkin/978-0-444-64062-8 (accessed 2024-02-25).
2. Thermal Analysis of Polymeric Materials; Springer-Verlag: Berlin/Heidelberg, 2005. https://doi.org/10.1007/b137476.
3. Duncan, J. Principles and Applications of Mechanical Thermal Analysis. In Principles and Applications of Thermal Analysis; John Wiley & Sons, Ltd, 2008; pp 119–163. https://doi.org/10.1002/9780470697702.ch4.