Viscoelastic relaxations in poly(ethylene-co-1-octadecene) synthesized by a metallocene catalyst

The viscoelastic relaxations of four copolymers of ethylene and 1-octadecene, with different comonomer contents, synthesized with a metallocene catalyst, have been analysed and compared to those of the corresponding polyethylene homopolymer. Similar to other ethylene copolymers, the temperature for α relaxation decreases with the increase in the comonomer content, attributed to the reduction of the crystal size. In fact, a linear relation has been found between the temperature location of α relaxation and the crystal thickness estimated from the SAXS long spacing. However, the position of β relaxation experiences very little dependence with the comonomer content and it overlaps to α relaxation for the higher comonomer contents. As to γ relaxation, there is also a clear effect of the comonomer content on the breadth and on the location of this relaxation.