The degradation and stability of polyethylene with small additions of metal oxides under UV-irradiation

The changes of the structure, physical and mechanical characteristics of the ethylene polymers with addition of Al2O3, SiO2, TiO2 and ZnO under UV-irradiation has been studied. It has been proved that effectiveness of protection of the polyethylene against UV-radiation depends on the nature, the structure of the crystal lattice and the dispersity of the introduced oxides. The two mechanisms of stabilization have been deduced by means of IR-spectroscopy, X-ray method, optical-microscopy and DTA analysis. It is a structure-physical mechanism with the additives TiO1, SiO2 and Al2O3, and photochemical one with ZnO. It has been found that photochemical light-stabilization is a very effective mechanism in comparison with the structure-physical one. This fact is confirmed by data on the oxygen absorption, of change in molecular mass and of decrease in the strength and deformability characteristics of the filled polyethylene during the process of UV-irradiation. (C) 1996 Elsevier Science Limited