Prediction of long‐term service performance of polymeric materials from short‐term tests: Creep and prediction of the stress shift factor of a longitudinal polymer liquid crystal

Abstract

The material studied is a longitudinal polymer liquid crystal (PLC). The creep behavior of the PLC is examined in the region of nonlinear viscoelasticity. The creep compliance D curves at nine different stress (T levels, from 10 to 50 J.cm3 at a constant temperature are determined and shifted along the log time axis for uRf = 10 J .to produce the D versus t/a, master curve. A fairly general formula for stress shift factor a , , based on free volume vf and the chain relaxation capability (CRC) derived by one of the authors is applied. The formula predicts values that agree with the experimental ones within the limits of the experimental accuracy. Thus, experiments at several stress levels can serve for prediction of longterm behavior from short-term tests. The same value of the Doolittle constant B is obtained separately from temperature shift and stress shift experiments for the PLC.

Sliding wear, viscoelasticity, and brittleness of polymers

“…(2) relies on an equation of state of the form v ‫ס‬ v(T,P), where T is the thermodynamic temperature and P is pressure. We have found that for all kinds of PBMs, including polymer liquid crystals (PLCs), which form a variety of phases, reliable predictions over decades of years are obtained 22,23,[25][26][27] when one uses the Hartmann equation of state 29 …”

“…9,10,[22][23][24][25][26][27] These methods rely largely on the concept of free volume v f . At higher temperatures (higher v f ) one observes at much shorter times creep and other property changes which at lower temperatures (lower v f ) would take years and decades (the time-temperature correspondence).…”

P–V–T properties of a polymer liquid crystal subjected to pre-drawing at several temperatures

“…In the beginning of this paper we have noted methods of prediction of service performance and service life of viscoelastic materials [6][7][8][9][10][11]. These methods cannot be applied to materials with voids.…”

“…Repeatedly, successful results have been obtained [9][10][11] by using the Hartmann EOS [17][18][19]. It reads…”

“…We would like to note, in particular, applications of these data for prediction of service performance and service life of polymers. Long-term (such as 50 years) service performance can be reliably predicted from shortterm (several hours) tests [6][7][8][9][10][11].…”