Dynamic Mechanical Analysis of Polymers and Rubbers

Abstract Dynamic mechanical analysis (DMA) is the technique of applying a stress or strain to a sample and analyzing the response to obtain phase angle and deformation data. These data allow the calculation of the damping or tan δ; the storage, loss, and complex modulus; as well as complex viscosity and complex compliance. Two approaches are used: (i) forced frequency, where the signal is applied at a set frequency and (ii) free resonance, where the material is perturbed and allowed to exhibit free resonance decay. Most modern DMA instruments are of the forced resonance type. In both approaches, the technique is very sensitive to the motions of the polymer chains and it is a powerful tool for measuring transitions in polymers. It is estimated to be 100 times more sensitive to the glass transition than differential scanning calorimetry (DSC) and resolves other more localized transitions not detected in DSC. In addition, the technique allows the rapid scanning of a material's modulus and viscosity as a function of temperature or frequency. DMA may also be referred to as dynamic mechanical thermal analysis (DMTA), dynamic mechanical spectroscopy (DMS), or dynamic thermomechanical analysis (DTMA).