Linear thermoviscoelastic creep behavior

In this section we analyze the results reported in [36]. The creep tests in the linear viscoelastic region were carried out at 14 temperatures in the range from 20°C to 160 C. In order for the creep behavior to stay in the linear region, it was necessary to reduce the stress gradually, together with the temperature increase. Thus, at 20°C the stress value was 20 MPa, while at 160 C it was only 0.2 MPa. In all cases, total 

Here B is the Doolittle constant, since Brostow derived his equation starting from the Doolittle formula relating viscosity and free volume [44]. The reduced quantities are 

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