Eur. Phys. J. E 2, 335-341
Ageing of natural rubber under stress
S.M. Clarke - F. Elias - E.M. Terentjev
Cavendish Laboratory, University of Cambridge,
Madingley Road, Cambridge CB3 0HE, UK
Received 22 November 1999 and Received in final form 18 January 2000
Abstract
We report a dynamical-mechanical study of stress
relaxation at small deformation in a natural (polyisoprene) rubber
well above its glass transition temperature 
.
We find
that an almost complete relaxation of stress takes place over very
long relaxation periods, even though the elastic network is
retained. The relaxation rate and the long-time equilibrium
modulus are sensitive functions of temperature which do not follow
time-temperature superposition. Many characteristic features of
non-ergodic ageing response are apparent at both short and very
long times. We interpret the observed behaviour in terms of the
nature of rubber cross-links, capable of isomerisation under
stress, and relate the results to recent models of slow glassy
rheology.
PACS
61.41.+e Polymers, elastomers and plastics. -
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances. -
83.50.By Transient deformation and flow; time-dependent properties: star-up, stress relaxation,
creep, recovery, etc.
Copyright EDP Sciences, Società Italiana di Fisica, Springer-Verlag
