Showing papers by "Rosario Benavente published in 1990"

Influence of chemical composition distribution and thermal history on the mechanical properties and viscoelastic relaxations of ethylene-1-butene copolymers

Abstract: The tensile drawing behaviour and the dynamic mechanical properties of four ethylene-1-butene copolymers, with nearly the same comonomer content but obtained with slightly different catalyst systems, have been analysed. It was found that the large strain mechanical properties and the strain-hardening behaviour seem to be affected by the degree of homogeneity in the distribution of comonomer along the different chains, reflecting the differences in the catalyst systems used. However, a parallel trend was not so clear for the small-strain dynamic mechanical properties for a particular thermal history, although the dependence of the relaxations on the crystallization conditions is evident.

Mechanical properties and dynamic mechanical relaxations of ethylene/alpha-olefin copolymers

Abstract: 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.