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Rate dependent and network phenomena in the multiaxial drawing of poly(vinyl chloride)

1995; Elsevier BV; Volume: 36; Issue: 2 Linguagem: Inglês

10.1016/0032-3861(95)91317-z

1873-2291

J. Sweeney, I. M. Ward,

Polymer Foaming and Composites

Stress-strain data have been obtained for poly(vinyl chloride) from drawing experiments in three stretching modes: uniaxial, planar and equibiaxial extension. The experiments were conducted isothermally at 84 °C, which is in the glass transition region, and at 90 °C, above Tg. The stress-strain behaviour is qualitatively different at the two temperatures. At the lower temperature, there is an initial stiff response followed by a decrease in slope suggestive of yielding, whereas this effect is absent at 90 °C. There is strain rate dependence at both temperatures, with stress simply related to the logarithm of the shear rate. To model the behaviour above the glass transition, strain rate dependence is included in a network model; the alternative of a time independent network acting in parallel with a yielding process is found to be inadequate. At the lower temperature, however, there is a need for such a process acting in parallel with the time dependent network in order to predict adequately the initial shapes of the stress-strain curves. The resulting constitutive equations provide very good representations at both temperatures.