Chemistry Reference
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matrix. This treatment explains the reason, why on the indicated part of
diagram s - e glassy polymer behavior is described excellently within the
frameworks of rubber high-elasticity concept [14]. Thus, polymers deforma-
tion processes on high-elasticity plateau within the frameworks of cluster
model are considered as the motion of connected with each other by the
chains stable clusters (with characteristic scale
l
st
) in devitrificated loosely
packed matrix (whose viscosity depends on relative fraction of fluctuation
free volume). The similar qualitative model of amorphous glassy polymers
deformation was proposed in Refs. [15, 16]. Let us also note, that accord-
ing to the model [17] external load cannot induce failure of crystallites with
stretched chains (CSC), having molecules axis parallel to tensile direction,
but can be induced randomly oriented instable clusters decay in loosely
packed matrix. Since the clusters are CSC analog [18], then this defines their
motion on loosely packed matrix possibility, not subjecting to decay. It is
easy to see, that the offered treatment gives physical picture, explaining all
The considered model of amorphous glassy polymers cold flow allows to
make two main conclusions [7].
Firstly, the cause of transition to turbulent regime is necessary to search
in loosely packed matrix high viscosity, owing to this its fraction, rejected by
cluster at its motion, gets into influence field of subsequent moving cluster
is, rejected by it and so on, that results to flow turbulent regime. It is obvi-
ous, that the higher cluster fraction is (or n
cl
, see the Eq. (1.11)) the stronger
process turbulence is expressed, that the plot of Fig. 6.1 reflects.
Secondly, preservation of stable clusters network with high density n
cl
on this part of diagram s - e explains high values s
p
, comparable with yield
stress value.
The authors of Ref. [19] used the stated above treatment of polymers
cold flow with application of Witten-Sander model of diffusion-limited ag-
gregation [20] on the example of PC. As it has been shown in Refs. [21,
22], PC structure can be simulated as totality of Witten-Sander clusters (WS
clusters) large number. These clusters have compact central part, which in
the model [18, 23] is associated with notion “cluster.” Further to prevent
misunderstandings the term “cluster” will be understood exactly as a com-
pact local order region. At translational motion of such compact region in
viscous medium molecular friction coefficient ξ
o
of each cluster, a particle,
having radius
a
, is determined as follows [24]:
ξ
o
= 6ph
o
a
,
(6.7)
