CHANGES IN THE AMORPHOUS PHASE OF POLYETHYLENE UPON HIGH EXTENSION

The structure of noncrystalline regions of HDPE oriented filaments prepared by two different techniques with various degrees of orientation lambda has been studied by density measurements, small-angle X-ray scattering and DTA. It is shown that at lambda > 10 the noncrystalline regions of the oriented structure prepared from a crystallized material have 80 nm voids (pores) in addition to an amorphous phase. The volume fraction of pores grows with increasing lambda. If a sample is prepared by crystallization from a pre-oriented melt, it does not contain discontinuities, and its noncrystalline regions consist of the amorphous material alone. In this case the density of the amorphous phase does not depend on the degree of sample orientation and has a constant magnitude typical of highly oriented PE samples.