FRACTAL MECHANICS OF ORIENTED POLYMERS - Fractal Mechanics of Polymers - page 268

In Ref. [25], it has been shown that the value E is defined by contribu-
tions by both clusters and loosely packed matrix. This fact is reflected in Fig.
14.4 by the dependence E (n cl ) for DV film samples, plotted according o the
data of Ref. [25]. However, the dependence of relaxation modulus E ¢ = 0 at
n cl = 0. This shows, that stress relaxation is realized completely in loosely
packed matrix of amorphous glassy polymer (see also Figs. 2.5 and 2.6). If
the data E (n cl ) for extrudates DV and DF-10 traced on the plots of Fig. 14.4,
then it turns out that they lie on the straight line E ¢ (n cl ), but not on E (n cl ).
The last circumstance assumes stress relaxation in loosely packed matrix of
extrudates DV and DF-10. Let us note, that the adduced above results ex-
plained causes of that fact, that extrudates elasticity modulus is smaller and
yield stress is Y is larger than for the same polymer film samples [24]. Reduc-
tion E for extrudates is due to mentioned above stress relaxation in loosely
packed matrix and, hence, its contribution in value E disappearance (Fig.
14.4). The s Y growth is due to in cl higher values for extrudates in comparison
with film samples ( Fig. 14.3 ), since the value is Y is defined by values n cl
only and is independent on loosely packed matrix properties (the Eq. (13.5)).
The indirect confirmation of this conclusion follows from the data of Ref.
[26], where polycarbonate samples tests, extrudated at different extrusion
temperatures T e , shown, that the smallest E values were obtained at T e > T g ,
in addition in this case the value E of extruded polycarbonate proves to be
lower than initial sample elasticity modulus.
FIGURE 14.4 The dependences of elasticity modulus E (1, 2, 3) and relaxation modulus
E ∞ (4) on entanglements cluster network density n cl for film samples DV (1, 4) and extrudates
DV (2) and DF-10 (3) [22].