Chemistry Reference
In-Depth Information
FIGURE 10.6
The dependence of impact toughness
A
p
on macromolecular entanglements
cluster network density in
cl
in double logarithmic coordinates for PASF aged samples [15].
It is easy to see, that the Eq. (10.13) power correlation supposes very
strong dependence of
A
p
on n
cl
. This observation was confirmed experimen-
tally. The in
cl
decrease approximately in 1.5 times results to
A
p
reduction
more than on order of magnitude [16]. The cause of such sharp
A
p
decrease
is weakening of shear mechanism (which is the most effective impact energy
dissipation mechanism) at n
cl
reduction. The similar relation between
A
p
and
n
cl
was obtained and for polyethylenes. The Eq. (10.13) together with the de-
pendence of in
cl
on molecular weight, adduced in Ref. [15], also explains the
strong dependence of PASF impact toughness on samples molecular weight
[19].
As it is known [20], the strain energy release critical rate
G
Ic
, which char-
acterizes value and its dependence on notch length a can be expressed as
follows:
2
K
,
(10.14)
Ic
Ga
-
d
1
G
=
~
⋅
r
Ic
I0
E
where
d
r
is also fractal dimension and the reasons of its special designation
will be considered below.
Attempts of the parameter
G
Ic
representation as a function
d
a
were
unsuccessful, since through this correlation is given by a straight line, it
r
-
1
