Chemistry Reference
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, during which polymer changes structure and properties in physical aging
process
(
)
tr
cr
tâ¤
.
As it is known [13], the value
A
p
increases at molecular mobility intensi-
fication and the latter is associated with chains mobility in polymer structure
loosely packed regions [71]. Within the frameworks of model [7] loosely
packed matrix, surrounding clusters is such region. Its relative fraction j
l.m.
can be determined according to the Eq. (2.4). In Fig. 10.20, the dependence
A
p
(j
l.m.
) is shown, which has the expected character. In conformity with the
data of Ref. [13]
A
p
linear growth at j
l.m.
increase is observed and the condi-
tion
A
p
= 0 is realized not at j
l.m.
= 0, what was to be expected, but at j
l.m.
â
0.352. This value j
l.m.
according to the Eq. (2.4) corresponds to j
cl
â 0.648,
that is close enough to the value
ag
ag
cr
c
Ï
at
T
= 293 K (~0.619). This corresponds
to the postulate of completely stretched chains at structure quasiequilibrium
state, restricting j
cl
growth, and completely inhibited owing to this molecu-
lar mobility, that defines the condition
A
p
= 0, that is, complete brittleness of
polymer [67].
FIGURE 10.20
The dependence of impact toughness
A
p
on loosely packed matrix relatively
fraction j
l.m.
for PC [67].
Thus, the theoretical description of physical aging process of amorphous
polymers (on the example of their typical representative-polycarbonate)
within the frameworks of fractal analysis and thermal cluster model. It has
