A. Akinay (1), W. Brostow (1,2), V. M. Castaño (1,2), R. Maksimov (3), P. Olszynski (4)

(1) Department of Materials Science, University of North Texas, Denton, TX 76203-5310, USA; brostow@unt.edu
(2) Department of Applied Phsyics and Advanced Technology (FATA), Universidad Nacional Autonoma de México, A.P. 1010, Queretaro , Qro. 76000, Mexico; castano@marta.phys.unt.edu
(3) Institute of Polymer Mechanics, The University of Lativa, 23 Aizkraukles iela, 1006 Riga, Lativa
(4) Institute of Material Science and Applied Mechanics, Wroclaw University of Technology, Smoluchowskiego 25, 50-370 Wroclaw, Poland

ABSTRACT

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 temperatures levels in the range between 20 and 100°C were used to create master curves for T(ref) = 20°C. The teperature shift factors a(T) were calculated using a general formula derived by one of us and based on free volume v(f) and the chain relaxation capability model.  The redicted values agree with the experimental ones for all materials studied within limits of the experimental acuaracy.  Moreover, the relation between the shift factor a(T) and the reduced volume v(~) 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.

Keywords: Time - temperature correspondence; Stress relaxation; Long-term polymer performance