Dynamic mechanical analysis (DMA)

What is DMA used for?

Dynamic mechanical analysis (DMA), also known as dynamic mechanical thermal analysis (DMTA), is a thermal analysis technique used to characterize material properties as a function of temperature, time, frequency, stress, and atmosphere, or a combination of these parameters.

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.

How does DMA work?

In DMA, 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.

Measured parameters

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 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. The parameter is important for determining the manufacturing conditions and malleability 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 directly affect the material's 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.

Do you need DMA laboratory services?

Measurlabs offers high-quality DMA analyses with fast results and competitive prices. Other thermal tests are also available, including thermomechanical analysis and rheology testing. If you have any questions about your sample or wish to discuss the most appropriate testing plan, our experts are always happy to help. You can contact us through the form below or at info@measurlabs.com.