Authors: Danilo Justino Carastan Nicole Raymonde Demarquette Alexandre Vermogen Karine MasenelliVarlot
Publish Date: 2008/05/07
Volume: 47, Issue: 5-6, Pages: 521-
Abstract
In this work the rheological behavior of block copolymers with different morphologies lamellar cylindrical spherical and disordered and their claycontaining nanocomposites was studied using small amplitude oscillatory shear The copolymers studied were one asymmetric starblock styrene–butadiene–styrene copolymer and four styrene–ethylene/butylenes–styrene copolymers with different molecular architectures one of them being modified with maleic anhydride The nanocomposites of those copolymers were prepared by adding organophilic clay using three different preparation techniques melt mixing solution casting and a hybrid melt mixing–solution technique The nanocomposites were characterized by Xray diffraction and transmission electron microscopy and their viscoelastic properties were evaluated and compared to the ones of the pure copolymers The influence of copolymer morphology and presence of clay on the storage modulus G′ curves was studied by the evaluation of the changes in the low frequency slope of log G′× logω ω frequency curves upon variation of temperature and clay addition This slope may be related to the degree of liquid or solidlike behavior of a material It was observed that at temperatures corresponding to the ordered state the rheological behavior of the nanocomposites depended mainly on the viscoelasticity of each type of ordered phase and the variation of the slope due to the addition of clay was small For temperatures corresponding to the disordered state however the rheological behavior of the copolymer nanocomposites was dictated mostly by the degree of clay dispersion When the clay was well dispersed a strong solidlike behavior corresponding to large G′ slope variations was observed
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