Chemistry Reference
In-Depth Information
FIGURE 2.4
The schematic dependences mechanical losses angle tangent tgd (1) and
fractal dimension of chain part between entanglements nodes
D
ch
(2, 3) on temperature
T
for
HDPE. The calculation of
D
ch
according to the equations: 2 - (2.8), model of fixed valent
angles, 3 - (2.16) [38].
Hence, the adduced above results shown that the main factor, influencing
on molecular mobility level in HDPE noncrystalline regions, is these regions
structure, characterized by fractal dimension
d
f
or relative fraction of lo-
cal order regions (clusters) j
cl
. Definite influence is exercised by molecular
characteristics, especially if to take into account, that between
d
f
and j
cl
, on
the one hand, and
S
and
C
∞
, on the other hand, the close intercommunication
exists (see, for the example, the Eqs. (1.11) and (1.12)). As consequence, the
equations using, taking into account their structural state, will be correct for
polymers dimension
D
ch
estimation [38].
Glassy state structural components distinction defines their behavior dis-
tinctions in both deformation [46] and relaxation [47] processes. It is known
[48, 49], that in its turn polymers glassy state includes a substates number,
differing by mechanical properties temperature dependences. A breaking
(bend) on the corresponding parameter dependence, for example, of yield
stress on temperature, is a typical indication of transition from one substate
to another. At present unequivocal structural identification of these states is
