Flow, high‐elastic (recoverable) deformation, and rupture of uncured high molecular weight linear polymers in uniaxial extension

Abstract

The behavior of narrow molecular weight distribution polymers has been investigated under uniaxial extension at constant deformation rate and at constant stress. It has been established that up to rupture these polymers behave as linear viscoelastic bodies. A detailed investigation of the rupture phenomenon has shown that the rupture of fluid polymers is due to their transition to the rubbery state at critical deformation rates, with the result that they disintegrate like quasi‐cured rubbers. The effect of the temperature and the molecular weight on the critical conditions of rupture has been described in terms of viscoelastic relaxation.

Catastrophic failure of polymer melts during extension

“…The imposed disturbances correspond (non-dimensionally) to the ones in figure 3. The SBR data show a large scattering, whereas the data from Vinogradov et al [1] show agreement with the calculated break, within the scattering of the measurements.…”

“…Figure 5 contains the break of rectangular shaped 240 kg/mole SBR samples from Wang et al [21]. These are shown together with the first published breaking study by Vinogradov et al [1] (data from their figure 1). They extended 'dog-bone' shaped PI, with a central cylinder of length L 0 = 30 mm and a radius of R = 2.5 mm, from the ends of the sample.…”

“…Basically, these were either the extension of a cylindrical shaped sample from the ends of the sample [1,11] with a fixture moving in the axial (e.g. extensional) direction, or the use of a dual-wind up system [2,3,20,21].…”

“…Non ideal conditions will develop in the preparation and handling of the polymer. Here the initial deviation from an ideal cylinder is imposed on the center of the sample (z = 0), although an observed break has not been reported to appear at any specific place on the sample [1,2,32]. Some theoretical studies suggest that the necking should be positioned at the center of the sample on theoretical ideal geometries [33,34].…”

“…Secondarily to discuss its consequences for the suggested cohesive type of failure mechanisms. As in most experimental studies [1,2,3,11,20,21] the focus will be on the extension and potential breakup of monodisperse polymer melts, applying narrow molecular weight distributed polystyrene (PS), polyisoprene (PI) and styrenebutadiene (SBR) melts.…”