Molecular association complex of urea with polyethylene. Morphology of urea-polyethylene complex and polyethylene crystals obtained from the complex

Abstract

We succeeded in preparing the urea-polyethylene complex by the addition of a previously formed urea-paraffin complex in xylene solution of polyethylene at 120°C. This is a substitution reaction in which the guest molecules were changed from paraffin to polyethylene. The reaction mechanism is discussed here. DSC thermal analysis of the urea-polyethylene complex shows that it has a higher melting temperature, 148°C, than either urea and polyethylene. X-ray diffraction measurements show that it has the same hexagonal unit cell dimensions as those of the urea-paraffin complexes. However, scanning electron microscopic observation shows it to have significantly different morphological features from those of the urea-paraffin complexes. The hexagonal prism-like crystal of the urea-polyethylene complex is composed of a number of lamella stacked regularly along the long axis of the crystal. Moreover, it is shown that the polyethylene crystals obtained from the urea-polyethylene complex have morphological features similar to those of the complex.