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EXHIBIT 1

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Meohamca] P1·opert1es
_ of
Sohd Polymers
I. M. Ward
Department of Physics,
The University of Leeds
WILEY-INTERSCIENCE
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Case 1:05-cv-00737-JJF Document 24-2 Filed 12/06/2006 Page 4 of 4
The Yield Behaviour of Polymers 271
fail catastrophically. Yet another type of polymer {a rubber) extends
homogeneously to rupture. A salient point to recognize is that polymers
in general show all these types of behaviour depending on the exact
conditions of test (Figure 1.1). This is quite irrespective of their chemical
nature and physical structure. Thus explanations of yield behaviour
which involve, for example, cleavage of crystallites or lamellar slip or
amorphous mobility are only relevant to specific cases. As in the case
of linear viscoelastic behaviour or rubber elasticity what we must hrst
seek is an understanding of the relevant phenomenological features,
decide on suitable measurable quantities and then provide a molecular
interpretation of the subsequent constitutive relations.
11.1 DISCUSSION OF LOAD—ELONGATION CURVE
The most dramatic manifestation of yield is seen in tensile tests when
a neck or deformation band occurs, as in Figure 11.1 (see Plate VIA). In
these cases the plastic deformation is concentrated either entirely or
primarily in a small region of the specimen. The precise nature of the
plastic deformation depends both on the geometry of the specimen and on
the nature of the applied stresses. This will be discussed more fully later.
The characteristic necking and cold—drawing behaviour is as follows.
On the initial elongation of the specimen, homogeneous deformation
occurs and the conventional load-extension curve shows a steady increase `
in load with increasing elongation (AB in Figure 11.2). At the point B
the specimen thins to a smaller cross—section at some point, i.e. a neck is
formed. Further elongation brings a fall in load. Continuing extension
B
Lood C
A
Extension
Figure 11.2. Typical load—extension curve fora cold·drawing polymer. “