Chemistry Reference
In-Depth Information
calculations parameters t
Y
and
G
cl
were replaced by s
Y
and
E
, respectively.
E
value is greater than the elasticity modulus
E
cl
due to the availability of
clusters, as it follows from the plots of Fig. 2.5 and 2.6. That is why to com-
pensate two mentioned effects the strain e
o
, estimated according to the Eq.
(4.11), was twice increased. The final equation looks as follows [24]:
s
e
≈
0, 64
Y
=
0, 64
e
,
(4.16)
0
cl
E
where e
cl
is the elastic component of macroscopic yield strain [38], which
corresponds to strains e
o
and
e
by the physical significance [37].
Combination of the Eqs. (4.14) and (4.16) together with the plots similar
to the ones shown in Figs. 2.5 and 2.6, wherefrom
E
cl
(
G
cl
) can be deter-
mined, allows to estimate theoretical yield stress
T
s
and compare it with
experimental values is
Y
. Such comparison is adduced in Fig. 4.7, which dem-
onstrates satisfactory conformity between
T
s
and s
Y
that proves the sugges-
tion made in the Ref. [24] and justifies the above-made assumptions.
FIGURE 4.7
The relation between experimental s
Y
and calculated according to the Eq.
(4.14) yield stress values for PAr (1) and PC (2) [24].
Hence, realization of the yielding process in amorphous glassy polymers
requires clusters stability loss in the mechanical stress field, after which me-
chanical devitrification of the loosely packed matrix proceeds. Similar crite-
rion was obtained for semicrystalline polymers [24].
