CRAZING - Fractal Mechanics of Polymers - page 186

crazing: a large S and C ∞ values (69.8 Ǻ 2 [27] and 10 [28], accordingly), that
defines high values d f and, hence, n [20].
FIGURE 9.2 The dependence of Poisson's ratio n on testing temperature T for PS (1), PC
(2) and PP (3). The horizontal shaded line shows the value n * [20].
In Fig. 9.3, the dependences n( K st ) for the considered epoxy polymers are
adduced where the value n * is indicated again by a horizontal shaded line.
As one can see, crazing is possible only for epoxy polymer samples with K st
= 0.50 and 1.50, having the smallest values of both n cl and chemical cross-
linking nodes density n c [29], that corresponds completely to the concepts of
Refs. [16, 30]. Exactly these epoxy polymers in compression testing show
brittle fracture (up to yield stress) that confirms experimentally the plots of
Fig. 9.3 correctness.
FIGURE 9.3 The dependence of Poisson's ratio n on the value K st for EP-1 (1) and EP-2 (2).
The horizontal shaded line shows the value n * [20].