Showing papers by "Rosario Benavente published in 2004"

Metallocenic copolymers of ethylene and 5,7‐dimethylocta‐1,6‐diene: Structural characterization and mechanical behavior

Abstract: The relationship between the structure and mechanical properties has been established for several copolymers of ethylene and 5,7-dimethylocta-1,6-diene synthesized with a metallocene catalyst. A dependence on the composition and polymerization temperature has been found. The branches cannot be incorporated into the orthorhombic crystal lattice, and consequently, structural parameters such as the crystallinity and crystal size are considerably affected as the 5,7-dimethylocta-1,6-diene content increases in the copolymers. The viscoelastic relaxations have been analyzed and compared with those exhibited by high-density polyethylene (HDPE). The β relaxation does not appear in HDPE and is exclusively seen in the copolymers. As the 5,7-dimethylocta-1,6-diene content rises, the intensity of this process is increased, and its location is shifted to a lower temperature up to comonomer contents of approximately 6–8 mol % in the copolymers. On the other hand, the α mechanism associated with motion within the crystalline regions is also moved to a lower temperature and its intensity is diminished as the 5,7-dimethylocta-1,6-diene molar fraction increases in the copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3797–3808, 2004

Oxygen permeability in blends of a vinyl alcohol/ethylene copolymer and a metallocenic ethylene/1‐octene copolymer

Abstract: This work describes the preparation, characterization, and evaluation of the oxygen permeability of blends based on a polyolefin synthesized with a metallocene catalyst (ethylene/1-octene copolymer) and a vinyl alcohol/ethylene copolymer in an attempt to establish the corresponding relationships between the composition, morphology, and transport properties to design materials with optimized and enhanced agricultural and food packaging performances. Moreover, microhardness measurements have been used to analyze the mechanical response of these blends and to obtain information about the dispersion of the two immiscible components within the blends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3766–3774, 2004