Chemistry Reference
In-Depth Information
clusters availability in the indicated semicrystalline polymers devitrificated
amorphous phase has quite another origin, namely, it is due to amorphous
chains tightness in crystallization process [48]. In practice this effect results
to the condition
D
> 0 realization, which in the low-molecular substances
case belongs to hypothetical non existent in reality transitions “an overheat-
ed liquid → solid body” [45].
im
(
)
-D
for
polymers with devitrificated (1, 7, 8, 9) and glassy (2, 3, 4, 5, 6, 10) loosely packed matrix
[43].
im
FIGURE 4.10
The correlation of yield strain e
Y
and parameter
exp
G
RT
Let us note one more feature, confirming existence reality of Fig. 4.10
plot left branch. At present e
Y
increase at
T
growth for polyethylenenes
and e
Y
decrease at the same conditions - for amorphous glassy polymers
are well-known [18]. One can see easily, that this experimental fact is ex-
plained completely by two branches availability in the plot of Fig. 4.10,
which confirms again existence reality of suprasegmental structures, which
are in quasiequilibrium with “free” segments. This quasiequilibrium is char-
acterized by
D
> 0.
As it was to be expected the value e
Y
= 0 at
D
so, that in this case
im
im
(
)
-D
D
=
0. The last condition is achieved at
T
=
T
g
, where the yield strain is always
equal to zero. Let us also note, that the data for semicrystalline polymers with
vitrificated amorphous phase (polyamide-6, poly(ethylene terephthalate))
cover the right branch of the Fig. 4.10 plot. This means, that suprasegmen-
im
exp
G
RT
or
im
