Effect of gamma irradiation on ethylene-octene copolymers produced by constrained geometry catalyst

Elastomeric ethylene-octene copolymers of differing molecular weights and c omonomer content were exposed to 25 kGy of gamma radiation from Co-60 sourc e in an inert atmosphere. Tests were performed to evaluate the changes in t he chemical, physical, and mechanical properties. All properties showed a d ependence on both composition and molecular weight. The effect of gamma irr adiation is most noticeable in the mechanical properties such as the tensil e modulus and elongation to break. The combination of the low octene-1 cont ent and high molecular weight leads to higher post irradiation tensile modu lus. FTIR spectroscopy studies indicate that formation of unsaturated chemi cal moities after irradiation of samples with same molecular weight occurs more readily in the lower octene-1 content copolymers. While at constant co mposition there is a preference for the higher molecular weight copolymers, The low molecular weight and low octene content copolymer showed some evid ence of polymer chain scission as the dominant effect. (C) 1999 Elsevier Sc ience B.V. All rights reserved.