Dynamic Mechanical Analysis

Dynamic Mechanical Analysis (DMA)

Dynamic Mechanical Analysis measures the mechanical properties of materials as a function of time, temperature, and frequency. The DMA Dynamic Mechanical Analysis instrument incorporates unique technology to provide the ultimate in performance, versatility, and ease-of-use. State-of-the-art non-contact, linear drive motor technology in our Dynamic Mechanical AnalysisDMA instruments provide precise stress control. Ultra-sensitive optical encoder Dynamic Mechanical Analysis technology is used to measure strain and air bearing technology insures virtually friction-free movement. The Dynamic Mechanical AnalysisDMA instrument operates over a wide temperature range (-150 to 600°C) and provides multiple modes of deformation including dual/single cantilever and 3-point bending, tension, compression, and shear. The clamps are individually calibrated for data accuracy and the elegant but simple design facilitates sample mounting.

What is the process for evaluating a DMA sample? NTS utilizes the TA INSTRUMENTS 2980 to perform DMA in accordance with ASTM E1640 using the single and dual cantilever beam and the three-point bending techniques. It is most useful for observing the viscoelastic nature of polymers. Two methods are currently used: One is the decay of free oscillations and the other is forced oscillation. Free oscillation techniques involve applying a force to a sample and allowing it to oscillate after the force is removed. Forced oscillations involve the continued application of a force to the sample. An oscillating force is applied to a sample of material and the resulting displacement of the sample is measured. This method is the most commonly used one today. Samples can be either solids or melts. Most solids are tested by linearly applied strains and melts or liquids are normally tested in shear.

Why perform DMA Analysis? The sample deforms under the load. From this the stiffness of the sample can be determined, and the sample modulus can be calculated. By measuring the time lag in the displacement compared to the applied force it is possible to determine the damping properties of the material. The time lag is reported as a phase lag, which is an angle. The damping is called tan delta, as it is reported as the tangent of the phase lag.

Effects and properties that can be characterized by the DMA:

  • Viscoelastic behavior
  • Crystallization and melting
  • Relaxation behavior
  • Gelation
  • Glass transition
  • Phase transitions
  • Mechanical modulus
  • Composition of blends
  • Damping behavior
  • Curing and polymerization reactions
  • Softening
  • Material defects
  • Viscous material flow
  • Effects caused by filler materials

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