Polymer large-strain cyclic deformation

In a previous article (2) we described a new approach to the analysis of nonlinear viscoelasticity as encountered in such large-strain cyclic deformation of polymers. In this chapter, we describe the apparatus used and the method of treating the data obtained. 

Measurement of Nonlinear Viscoelastic Properties of Polymers in Cyclic Deformation under a Relatively Large Strain Amplitude... 

The viscoelastic response of polymer melts, that is, Eq. 3.1-19 or 3.1-20, become nonlinear beyond a level of strain y0, specific to their macromolecular structure and the temperature used. Beyond this strain limit of linear viscoelastic response, if, if, and rj become functions of the applied strain. In other words, although the applied deformations are cyclic, large amplitudes take the macromolecular, coiled, and entangled structure far away from equilibrium. In the linear viscoelastic range, on the other hand, the frequency (and temperature) dependence of if, rf, and rj is indicative of the specific macromolecular structure, responding to only small perturbations away from equilibrium. Thus, these dynamic rheological properties, as well as the commonly used dynamic moduli... 

The creation of the triple-shape capability for an AB polymer network system by a simple one-step process similar to a conventional dual-shape progranuning process was shown for networks based on PCL and PCHMA [24] (see Sect. 2.4). In these materials a stress-controlled cyclic, thermomechanical experiment was used to quantify the triple-shape effect. The sample was deformed at 150°C (liigh) to 50% (Ein) and subsequently cooled to —10°C (Tio ). The large temperature interval of around 160 K led to a strong reduction of the strain. When the sample was heated... 

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