In the previous chapters the processability of gum rubber was related to its behaviour at large
deformation and fracture. A given rubber has a unique deformational behaviour, which may be
characterised by its viscoelastic properties. The latter is, in turn, related to the molecular
architecture. Therefore, viscoelastic properties play a central role in relating polymerisation
conditions to processability of gum rubber. The viscoelastic characterisation has particular
importance for gum rubbers, because many of them contain an insoluble fraction called ‘gel’, which
makes solution-based characterisation inapplicable.
In this chapter, a development of the viscoelastic characterisation method is described. It begins
with methods of describing deformation behaviour, subsequently a treatment of non-linear
viscoelasticity is presented. Finally, by using the viscoelastic characterisation method, the
processability of gum rubber is related to its molecular architecture.
6.2 Methods of describing deformation
When the subject of deformation of rubber is considered, a conventional approach such as shear or
elongation is accepted. The definition of steady state viscosity is an example of the former and
that of tensile testing is an example of the latter. However, the deformation of rubber during
mixing is not completely shear nor elongation. Therefore, the way to describe this deformation
needs to be examined. The bulk compression need not be considered, because rubber is practically
incompressible.
For simplicity, consider an elastic body which is in isolation. The deformation of this body may be
described by the stress tensor ?ij and the deformation tensor ?ij as:
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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