Time-temperature correspondence prediction of stress relaxation of polymeric materials from a minimum of data

We have determined the stress relaxation of a longitudinal polymer liquid crystal (PLC), polypropylene and their blends containing 10 and 20% of the PLC at the constant strain of 0.5%. The results for nine temperature levels in the range between 20 and 100 C were used to create master curves for T-ref = 20degreesC. The temperature shift factors a(T) were calculated using a general formula derived by one of us and based on free volume of and the chain relaxation capability model. The predicted values agree with the experimental ones for all materials studied within limits of the experimental accuracy. Moreover, the relation between the shift factor a(T) and the reduced volume (ν) over bar has been used to predict long-term behavior of the materials from a minimum (at least two sets) of data-providing also in this case reliable results. (C) 2002 Elsevier Science Ltd. All rights reserved.