THE DEGRADATION AND STABILITY OF POLYETHYLENE WITH SMALL ADDITIONS OFMETAL-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 un der UV-irradiation has been studied. It has been proved that effective ness of protection of the polyethylene against UV-radiation depends on the nature, the structure of the crystal lattice and the dispersity o f 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 addit ives TiO1, SiO2 and Al2O3, and photochemical one with ZnO. It has been found that photochemical light-stabilization is a very effective mech anism in comparison with the structure-physical one. This fact is conf irmed by data on the oxygen absorption, of change in molecular mass an d of decrease in the strength and deformability characteristics of the filled polyethylene during the process of UV-irradiation. (C) 1996 El sevier Science Limited