Chemistry Reference
In-Depth Information
very fast
L
growth. Let us consider the conditions of transition from part II
cording to the indicated above reasons it assumption
D
ch
= 1.0, that is, part of
chain, stretched completely between clusters, let us obtain [73]:
LR
l
l
cl
=
cl
,
(4.41)
l
st
st
That is, drawing ratio critical value l
cr
, corresponding to the transition
from part II to part III (from fractal behavior to Euclidean one) or the transi-
tion from yielding to cold flow, is equal to [73]:
L
Rl
l =
cl
,
(4.42)
cr
cl st
that corresponds to the greatest attainable molecular draw [81].
For PC at
T
= 293 K and the indicated above values
L
cl
and
R
cl
l
cr
will be
equal to 2.54. Taking into account, that drawing ratio at uniaxial deformation
l
"
cr
=
1/3
c
l
, let us obtain l
"
cr
= 1.364 or critical value of strain of transition.
Let us note that within the frameworks of the cluster model of polymers
amorphous state structure [18] chains deformation in loosely packed ma-
trix only is assumed and since the Eq. (4.42) gives molecular drawing ratio,
which is determined in the experiment according to the relationship [81]:
(
)
eeφ
=
′′
1
-
.
(4.43)
cr
cr
c
l
Let us obtain e
cr
= 0.117 according to the Eq. (4.43). The experimental
value of yield strain e
Y
for PC at
T
= 293 K is equal to 0.106. This means,
that the transition to PC cold flow begins immediately beyond yield stress
that is observed experimentally [23].
Therefore, the stated above results show, that the assumed earlier sub-
states within the limits of glassy state are due to transitions from deforma-
tion in Euclidean space to deformation in fractal space and vice versa. These
transitions are controlled by deformation scale change, induced by external
load (mechanical energy) application. From the physical point of view this
postulate has very simple explanation: if size of structural element, deform-
ing deformation proceeding, hits in the range of sizes
L
min
-
L
max
(Fig. 1.2),
then deformation proceeds in fractal space, if it does not hit - in Euclidean
one. In part I intermolecular bonds are deformed elastically on scales of 3 ÷
4Å (
L
<
L
min
), in part II - cluster structure elements with sizes of order of 6
