This thesis is concerned with the use of rheological equations
of state to describe the behaviour of vulcanised elastomers and, in
particular, vulcanised elastomers loaded with carbon black. The
properties of these materials are dependent upon the specific
combination of elastomer and carbon black, and the effect of carbon
black loading is studied by means of experiments on a
butadiene-acrylonitrile base polymer KRYNAC 806, unfilled and loaded
with 50phr SRF N774 carbon black.
The first part of this work concerns small ampIitude
oscillatory shear experiments carried out on a Weissenberg
rheogoniometer over a range of amplitudes, frequencies, and
temperatures. Both materials are found to remain within the linear
viscoelastic region for temperatures greater than about -10°c, to
obey the time-temperature superposition principle, and to have
identical shift factors. Dynamic moduli over a reduced frequency
range of about ten decades of log frequency are characterised by the
Huet model.
The second part concerns finite deformation experiments
consisting of prestraining samples in simple tension and applying
small axial oscillations when stress relaxation is almost complete.
Dependencies of the incremental dynamic moduli measured in this way
are investigated with regard to frequency and extension ratio.
Moduli measurements indicate that the time dependence of the
materials is unaffected by deformation, although relaxation spectrum
functions for the filled sample are strain dependent. A criterion is
established for testing whether results can be modelled by a certain
class of non-linear viscoelastic constitutive equations. A
constitutive equation is proposed which represents the strain
dependence of moduli for both the filled and unfilled materials.
Other published data are shown not to conform to the above criterion.
It is also shown that despite this fact, in some cases at least, the
proposed constitutive equation provides a better represent at ion of
published data than other constitutive equations which have hitherto
been applied.
Date of Award | 1988 |
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Original language | English |
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Awarding Institution | |
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THE RHEOLOGY OF UNFILLED AND CARBON BLACK LOADED ELASTOMERS
RUDDOCK, N. (Author). 1988
Student thesis: PhD