| The stress relaxation behaviour of roll-drawn polypropylene was investigated at ambient and elevated temperatures. The orientation was produced by roll drawing. The ensuing stress relaxation decreased in rate as the draw ratio increased, towards an equilibrium stress which decreased with increasing temperature. The Boltzmann superposition principle with either a three-element Maxwell model with an additional equilibrium modulus, or else the Kohlrausch model E(t) = E... |
