Chemistry Reference
In-Depth Information
where
r
p
and d are length and opening of ZD respectively. Both indicated
5.2
).
FIGURE 5.3
The electron microphotographs of ZD surfaces (a) and sample elastically
deformed part (b) for PASF film, prepared from chloroform. Enlargement 5625× [21].
It is well-known [25], that limiting strain value for polymers grows
at molecular weight of polymer chain part between entanglements nodes
ing the indicated character. The shown in this figure dependence of l
ZD
on
molecular weight
M
e
between macromolecular binary hooking's reveals
the opposite tendency. This allows to assume, that in PASF glassy state
ZD parameters are controlled by macromolecular entanglements cluster
network. The comparison of l
ZD
values and
determined experimentally
draw ratio at failure l
e
for these PASF samples without notch, and tensile-
tendencies of these parameters are very close. It is known [20], that both
crazes and ZD are formed by locally oriented polymer and differed by
availability and absence of microvoids. The last availability in crazes de-
fines entanglements “geometrical loss” necessity [20], in virtue of that
draw ratio in craze fibrils is higher than l
e
. The equality of l
e
and l
ZD
testi-
fies, that in ZD entanglements loss does not occur. Thus, polymer drawing
in ZD is practically never not differed from the same sample without notch
drawing with the exception of its local concentration at notch tip, which is
stress concentrator.
