Dynamic mechanical testing phase angle

Fig. 32. Simple relationship between stress (a) and strain (e) in dynamic mechanical tests illustrating the role of the phase angle, showing (a) Hookian elastic response, (b) viscoelastic response, and (c) vectorial representations of complex oscillatory stress/strain response (74).

Dynamic mechanical analysers, as discussed in chapter 9, can be constructed so that they can be used with unvulcanised materials and, hence, the in phase and out of phase components of modulus and the loss angle measured. The usual test piece geometries for cured rubbers are not convenient for the uncured materials where some form of oscillating shear is probably the best approach. This is the geometry used in cure meters discussed in the next section and such instruments have formed the basis for apparatus which measures dynamic properties from before and through the curing process. 

Tan Delta n Mathematically expressed as the loss modulus divided by the storage modulus, the tangent of the phase angle between an applied stress and the strain response in a dynamic experiment. NOTE - Tan delta versus temperature curves are commonly reported in dynamic mechanical analysis (DMA) tests. 

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