FRACTAL MECHANICS OF ORIENTED POLYMERS - Fractal Mechanics of Polymers - page 267

The authors of Ref. [21] supposed, that in orientational drawing process of
poly(metyl methacrylate) (PMMA) the following structure changes occur:
the transition to more equilibrium structure owing to molecular package im-
provement and internal stresses relaxation. The quantitative structural model
absence not allows the authors of Ref. [21] to give direct proofs of their
suppositions. In Ref. [22] such treatment was fulfilled on the example of
extruded amorphous polyarylates DV and DF-10 with the cluster model of
polymers amorphous state structure using [12, 23].
In Fig. 14.3, the dependence of macromolecular entanglements cluster
network density n cl , which is as a first approximation measure of segments
number in local order regions (clusters) and, hence, measure of such order
degree, on extrusion draw ratio l for polyarylates DV and DF-10 is adduced.
The corresponding value n cl of sample, prepared by pressing under pres-
sure, was accepted as the value n cl for nonoriented DV sample [24]. As one
can see, polyarylates extrusion results to essential (more than in 1.5 times)
sample ordering degree increase, in addition this effect is reached even at l
≈ 2 and a further l growth the value n cl is practically not changed.
FIGURE 14.3 The dependence of entanglements cluster network density n cl on extrusion
draw ratio l for polyarylates DV (1) and DF-10 (2) [22].
The increase of n cl according to the Eq. (1.11) means j cl growth and j cl
enhancement according to the Eq. (1.12) assumes d f reduction. Thus, the
comparison of the plots of f Fig. 14.1 a nd 14.3 assumes, that for semicrystal-
line and amorphous glassy polymer l growth results to structure diametri-
cally opposite changes - for the first this is d f enhancement, for the second
- its reduction.