Chemistry Reference
In-Depth Information
FIGURE 9.1
The experimental dependences of limiting draw ratio in craze l
c
(1) and ZD
l
ZD
(2) on testing temperature
T
for PC according to the data of Ref. [15]. 3 - calculation
according to the Eq. (5.8) [16].
Plammer and Donald [15] have measured the draw ratio value l
c
and
l
ZD
for crazes and ZD, respectively, in PC, the temperature dependences of
which are adduced in Fig. 9.1 (the curves 1 and 2). The value l
c
begins to
increase sharply at
T
≈ 383 K (compare with
T
g
'
for PC) and the value l
ZD
remains approximately constant. The limiting draw ratio theoretical value in
crazes can be determined according to the Eq. (5.8). The results of the car-
ried out by such mode calculation of l
c
and l
ZD
for PC are presented in Fig.
9.1 by the points and their comparison with the experimental data of Ref.
[15] is very interesting. Let us indicate first of all, that at calculation the clus-
ter structure corresponding characteristics (
L
cl
and
R
cl
) were used as
L
e
and
d
e
. In the crazing region for PC (as it was noted above, this region beginning
corresponds to
T
g
'
) the calculated and experimental values l
c
are coordinated
excellently, that is unexpectedly accounting for the fact that the results were
obtained in different laboratories and for PC different marks. In the realiza-
tion ZD region (
T
< 343 K) the values l
ZD
are coordinated well enough by
both temperature dependences course and absolute values (the discrepancy
does not exceed 15%). But the theory and experiment comparison result
in transitional region from ZD to crazes (
T
= 333 ÷ 373 K) is the most in-
teresting, from which it follows that necessary for the indicated transition
macromolecular entanglements network density decreasing and, hence, l
