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Relaxation time of a polymer glass stretched at very large strains

The polymer relaxation dynamic of a sample, stretched up to the stress hardening regime, is measured, at room temperature, as a function of the strain $λ$ for a wide range of the strain rate $\dotγ$, by an original dielectric spectroscopy set up. The mechanical stress modies the shape of the dielectric spectra mainly because it affects the dominant polymer relaxation time $τ$, which depends on $λ$ and is a decreasing function of $\dotγ$. The fastest dynamics is not reached at yield but in the softening regime. The dynamics slows down during the hardening, with a progressive increase of $τ$. A small inuence of $\dotγ$ and $λ$ on the dielectric strength cannot be excluded.