ABSTRACT
Polyolefins are semicrystalline polymers, so the low-molecular-weight substances penetrate
and diffuse only in the amorphous phase. Each pair of particles in the polymer is surrounded
by the segments of a macromolecule. The cage formed by the polymer segments is more tight
than that of the liquid. The probability e for a pair of radicals to go out of the cage is
sufficiently less in polymer than in the liquid. The study of the cage effect and molecular
mobility in plasticized polypropylene (PP) proved the important role of not only the trans-
lational diffusion but also that of the rotational diffusion in the fate of a radical pair in the
polymer cage [1-3] (see Chapter 3). The initiation rate constant is ki¼ 2ekd, where kd is the decomposition rate constant (for the values of kd of initiators, see Chapter 3). The e values for
the most popular initiators are given in Table 13.1. They are sufficiently lower than those in
the liquid phase (see Chapter 3 and Ref. [4]).
