Ultimate regimes of deformation of linear flexible chain fluid polymers

Abstract

At temperatures far from the glass transition temperature linear flexible chain high polymers of narrow MMD when being deformed may undergo a transition from the fluid to the forced high elastic (and the glass) state. In simple shear, uniaxial extension and in the triaxial stressed state the transition of polymers to the forced high elastic state is accompanied by their rupture. Of decisive importance for this transition is the combination of the rate and amount of deformation. On the other hand, such a transition occurs at stresses which vary by 10–20 times for the various homologous series of linear flexible chain polymers. We have established unexpectedly simple relations connecting the parameters that characterize the rheological properties of polymers at deformation rates and stresses tending to zero with their ultimate strength and long term durability. This is determined by the fact that the polymers under consideration behave like linear bodies until they are fractured (in terms of the theory of linear viscoelasticity). From this it may be inferred that the selection of the simplest (as to composition) polymers having a highly homogeneous entanglement network plays a decisive role in the elucidation of the fundamental specificity of the rheological properties of polymeric systems.