Transition of polymers from the fluid to the forced high-elastic and leathery states at temperatures above the glass transition temperature

The transition from the fluid to the forced high-elastic (rubber-like or quasi-vulkanizate) state and then to the leathery state (that is between rubbery and glassy states ∗∗ ∗∗ FHES and FLS in abbreviated form ) has been systematically studied by increasing stresses and deformation rates, using an uncured high molecular-mass 1, 2-polybutadiene characterized by a rather high glass transition temperature (−18°C). Investigation of polymers in simple shear is possible up to critical stresses corresponding to the transition of fluid polymers to FHES. Uniaxial extension offers wide possibilities for characterizing polymers in FHES and FLS since it covers the range of 4–6 decades of deformation rates over the range of simple shear. The deformability of polymers is limited by their fracture even in FHES, and the fracture process is determined only by recoverable deformation. The failure envelope covering FHES and transition to FLS has been constructed and the long-term durability in the range of 7 decades of time measured. The maximum extensibility corresponding to the transition of the polymer to FLS is determined by the ultimate extensibility of macromolecular coils. Over a wide range of stresses the polymer behaves like a linear viscoelastic body. This makes it possible to correlate the data obtained for uniaxial extension and low-amplitude sinusoidal shear deformation, which is important for the prediction of fracture phenomena by means of the low amplitude non-destructive dynamic method.