THE FORMATION OF NONCRYSTALLINE DOMAINS I N POLYETHYLENE AT HIGH DRAWRATIOS

The structure of noncrystalline domains in oriented films and film-bas ed fibers of low-pressure polyethylene is studied by densimetry, DTA, and small-angle X-ray scattering. The dependence of the structure on t he preparation mode and the degree of orientation of the fiber is cons idered. It is demonstrated that noncrystalline domains of oriented str uctures produced from crystallized material at draw ratios lambda > 10 contain, in addition to the amorphous phase, a certain amount of 800- mum pores. The volume fraction of the pores increases with an increase in the draw ratio. The samples obtained by crystallization from a pre liminarily oriented melt are continuous; noncrystalline domains of suc h samples consist only of an amorphous phase and contain no voids. The density of the amorphous phase in this case does not depend on the de gree of orientation: it is constant and has a value typical for highly oriented polyethylene.