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The effect of orientation on the morphology and viscoelastic response of vinyl alcohol‐ethylene copolymers
Author(s) -
Cerrada María L.,
Benavente Rosario,
Pérez Ernesto,
Pereña José M.
Publication year - 2000
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20000901)201:14<1858::aid-macp1858>3.0.co;2-a
Subject(s) - copolymer , viscoelasticity , vinyl alcohol , materials science , relaxation (psychology) , ethylene , glass transition , polymer chemistry , morphology (biology) , dynamic mechanical analysis , composite material , chemistry , polymer , organic chemistry , catalysis , psychology , social psychology , biology , genetics
The influence of the main variables (temperature and strain rate) of the drawing process on the structure and dynamic mechanical relaxations of vinyl alcohol‐ethylene (VAE) copolymers with higher content in the former counit is studied. The structure of VAE copolymers is considerably modified by drawing, which produces a disordered crystalline form, as revealed by WAXD and DSC measurements. The structural changes have significant effects on the viscoelastic relaxations of stretched VAE copolymers. A remarkable increase in the storage moduli is observed in the direction parallel to the uniaxial orientation, depending on composition and drawing parameters. The drawn copolymers show an additional α relaxation taking place at temperatures higher than that of the α relaxation (glass transition), attributed to motions within the crystalline regions. The β mechanism is moved to higher temperatures for the stretched specimens and its intensity is considerably increased. Finally, the γ relaxation is very weak and only displayed in the sample with the higher ethylene content.