High temperature creep of polyvinyl chloride

Abstract

The creep behaviour of polyvinyl chloride (PVC) has been studied in the temperature range 280 to 340° F under constant stress varying from 3.4 to 22.7 p.s.i. It is shown that the steady-state creep rate is an exponential function of stress as suggested by Norton but the exponent decreases with temperature. The activation energy for creep is determined using an activated-state rate process and it is found to be a decreasing function of stress with a higher value at temperatures 320° F and above. It is shown that the time dependent strain can be represented by

$$\gamma = \gamma _0 + \dot \gamma _s t + \gamma _T \left[ {1 - \exp \left( { - K\dot \gamma _s t} \right)} \right]$$

where γ ₀ is the instantaneous strain on stressing, $\dot \gamma _s$ the secondary creep rate, γ _T transient strain, and K is a constant. Scanning electron micrograph studies of the fracture surface and the change in activation energy apparently support the probability of two different deformation mechanisms i.e., domain flow and chain segmental or molecular flow at temperatures below and above 320° F, respectively.