Chemistry Reference
In-Depth Information
T
e
calculated by the indicated method and
obtained experimentally ef
f
values of fracture strain for B-PES is adduced.
As follows from the adduced data, the good correspondence of
T
e
and e
f
is
obtained, particularly taking into account low precision of ef
f
determination
in this strains range. Besides, the theoretical calculation gives the greatest
e
f
value for free-defects samples that in practice is achieved with difficulty,
particularly for brittle polymers. Therefore, for the data of Fig. 7.6 the ex-
pected condition
T
e
> e
f
is carried out.
From the Eqs. (1.12), (2.3), (2.16), (4.39), (4.40), (7.9) and (7.11)
comparison it is easy to see, that the value ef
f
is determined in fact by two
parameters, namely,
D
and
S
. The side groups availability in the given
case plays a dual role. On the one hand, their availability results to D
growth and, consequently,
d
f
according to the Eq. (2.3) that should result
to e
f
increase owing to j
cl
reduction. On the other hand, the side groups
availability results to
S
rising, that should result to an opposite effect.
Thus, in order to obtain polymers, having side groups, with large deform-
ability the two following conditions fulfillment is required. Side groups
should increase
D
as much as possible and at the same time to rise S as
little as possible. For copolymers B-PES
S
enhancement effect prevails
on dicarbaminediphenyloxide (bromine-containing monomer [42]) con-
tents
C
B
are shown for B-PES and three hypothetical polymers, having
the same characteristics as B-PES, excluding S. As for these hypotheti-
cal polymers the following values were chosen: 30.7 Å
2
(polycarbon-
ate), 22.0 Å
2
(polyformal) and 18.7 Å
2
(polyethylene) [45]. As follows
from the data of Fig. 7.7, S reduction from ~41.5 ¢ 60.4 Å
2
for B-PES
up to 18.7 Å
2
for polyethylene results to ef
f
increase in about 40 times.
Therefore, in B-PES case the increase S effect prevails owing to the side
groups introduction.
