Dynamic Mechanical Analysis (DMA)
Dynamic Mechanical Analysis (DMA) is a technique used to characterize materials, specifically polymers. It applies a displacement to a sample and measures the mechanical response of the bulk material in a controlled temperature environment.
Dynamic mechanical analysis test conditions can be designed to study bulk mechanical properties of organic polymers to assist in determining key functional behavior related to:
Elasticity: Polymer resistance to permanent deformation due to resiliency of structure (recovery; stiffness)
Viscous Response: Deformation without breaking due to dissipation of mechanical energy by internal friction (damping)
DMA testing involves selection of the appropriate conditions of time, temperature, displacement and frequency to study the properties of interest. Some example selections are:
- Frequency sweep: frequencies can be specified to study the mechanical behavior of the sample as a function of oscillatory loading rate.
- Temperature ramp or isothermal temperature: precision heating and cooling allows the study of mechanical response as a function of temperature.
- Displacement modes:
- Tensile (stretch) for thin films and fibers
- Flexural (bend) for filled and crystalline polymers, thermoplastic polymers, thermosetting resins, elastomers.
- Controlled force / displacement: non-oscillatory test that measures mechanical response after applying instantaneous force or displacement distance.
- Creep/recovery test
- Stress relaxation test
- Force ramp (Young’s Modulus, linear modulus of elasticity) – “mini-tensile tester”
Examples of the various properties that can be measured through select test conditions:
- Storage Modulus
- Complex Modulus
- Loss Modulus
- Tan Delta
- Creep Compliance
- Storage/Loss Compliance
- Relaxation Modulus
- Sample Stiffness
- Young’s/Linear Elastic Modulus
- Transition Temperatures (e.g. Tg)
- Secondary Transitions (e.g. β)