Abstract
Methods have been developed for the computer simulation of stress relaxation in dense polymer melts using non-equilibrium molecular dynamics. In previous applications of these techniques we have used chain models that incorporate various features of real polymers. In the present work we extend the formulation to include a torsional potential that hinders free rotation about backbone bonds of the chain. The principal effect of the torsional potential in the present context is to shift the temperature level of the relevant phenomena upward to more reasonable levels. The principal conclusions drawn from the present simulations, as from the previous simulations in which the torsional potential is absent, are as follows. (i) Except at very early times, the non-bonded interactions make the primary contribution to the deviatoric stress during the constant strain-rate loading process simulated. (ii) The results for the stress relaxation modulus for simulations at various temperature levels may be reduced to a single master curve by suitable time shift. (iii) The shift factors required to produce a single master curve are found to obey the WLF equation, with reasonable values for the parameters in that equation.
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More From: Modelling and Simulation in Materials Science and Engineering
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