MECHANICAL-PROPERTIES AND DYNAMIC MECHANICAL RELAXATIONS OF ETHYLENE ALPHA-OLEFIN COPOLYMERS

The tensile drawing behaviour and the viscoelastic relaxations of three different copolymers of ethylene, containing 1-butene, 1-hexene and 4-methyl-1-pentene as comonomer, have been studied. The composition of the copolymers is increasingly poorer in comonomer following the above order. However, they show similar mechanical properties, both large-strain and small-strain dynamic mechanical, because the minor differences which have been found can generally be explained by the thermal and mechanical histories of the samples. Thus, it seems that the higher disrupting effect produced in the copolymer structure by the comonomers of greater size and volume is counterbalanced by the corresponding smaller concentration, and that only thermal treatment produces appreciable differences in properties.