Dynamic Mechanical Analysis (DMA)
Dynamic mechanical analysis (DMA) is a technique used in material characterization. The sample material is exposed to oscillating stress forces at a controlled temperature, and the observations are reported as changes in stiffness and damping. DMA can be used, for example, to obtain information on the modulus and other elastic and viscous properties of polymeric materials.
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What is DMA?
Dynamic mechanical analysis (DMA), also known as Dynamic Mechanical Thermal Analysis (DMTA), is a thermal analysis technique used to measure the dynamic properties of materials. DMA can characterize material properties as a function of temperature, time, frequency, stress, and atmosphere, or a combination of these parameters.
In dynamic mechanical analysis, the sample material is exposed to oscillating stresses at a set frequency under a controlled temperature, while the stiffness and damping are measured simultaneously. Oscillating stresses can be induced to the material as stress or strain forces, with a variety of loading modes. DMA measuring devices tend to have a wide operating temperature range, typically from -150 °C to 600 °C.
DMA is often used to analyze the mechanical properties of polymeric materials, as they are highly sensitive to temperature and stress frequency. DMA can also characterize transformation temperatures, such as glass transition and melting, which are essential for process tuning and material validation. Furthermore, DMA is often used as a part of material development, where the goal is to develop a material that can withstand desired temperatures, atmospheres, and physical strain.
DMA in mechanical engineering
Since dynamic mechanical analysis is used to study the mechanical and dynamic properties of materials, it is a widely used tool in mechanical engineering, more specifically polymer engineering. The use of DMA became common as different plastic and polymer materials started to replace more traditional materials.
What does DMA measure?
Depending on the characteristics of the tested material, DMA can be used to measure viscosity or elasticity. More precisely, DMA measures stiffness and damping. These are reported as modulus (stiffness) and loss tangent (damping). The modulus can be further divided into storage (G’) and loss modulus (G’’), which are the elastic and viscous components, respectively.
Modulus is the measure of the sample’s elastic behavior, whereas damping explains the dissipation of energy under cyclic load. Damping gives information about the material’s ability to absorb energy. Both modulus and damping vary with the state of the material, its temperature, and with the frequency of stress targeted at the sample. Storage modulus is not the same as Young’s modulus (E), which can be obtained from a tensile test.
DMA is also a great tool for determining the phase transition temperatures, such as the glass transition temperature (Tg) of a material. Glass transition is a second-order transition temperature where the material transforms from a hard and “glassy” state into a more viscous or rubbery state. Glass transition temperature is an important parameter in determining the manufacturing conditions and applicability of plastic materials.
DMA can also be used to study curing kinetics, including the point of vitrification and the point of gelation of thermosetting materials.
Sample requirements and preparation
DMA sample preparation is very important because the purity, uniformity, and dimensions of the sample directly affect its mechanical properties. DMA is suitable for solids, liquids, and gel-like materials. The sample geometry depends on the sample’s physical state at the beginning of the experiment and the desired type of experiment. Typical sample fixtures include single cantilever, dual cantilever, 3-point bending, tension, compression, and shear. For samples that cannot support their own weight, a special fixture can also be used.
Need a DMA analysis?
We offer high-quality DMA analyses with fast results and competitive prices. If you have any questions about your sample or testing plan, our experts are always happy to help. You can contact us through the form below or by emailing us at firstname.lastname@example.org.
Suitable sample matrices
Ideal uses of DMA
- Viscosity and elasticity measurements
- Glass transition temperature
- Polymer structure characterization
- Mechanical testing of plastics
- Curing kinetics testing
- Flow and relaxation behavior testing
Frequently asked questions
DMA is commonly used for analyzing the characteristics of different polymeric materials. Typical measurements are viscosity and elasticity measurements, polymer structure characterization, flow and relaxation tests, and glass transition temperature.
DMA is known to have possible inaccuracies due to inaccurate sample dimensions and uniformity. Modulus values can be incorrect if the sample shape is even slightly uneven. Furthermore, the mechanical energy from the oscillating stress directed at the sample is transformed into heat energy and can thus increase the temperature of the sample, causing inaccurate measurements.
Different plastics, elastomers, ceramics, metals and adhesives are suitable for DMA analysis.
Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.
When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.
Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.