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An investigation of shear‐induced mixing in the PSAN/PMMA blend
Author(s) -
Papathanasiou T. D.,
Higgins J. S.,
Soontaranun W.
Publication year - 1999
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.11633
Subject(s) - materials science , mixing (physics) , shear (geology) , composite material , polymer science , quantum mechanics , physics
Abstract We investigate experimentally the effect of steady‐state simple shear flow on the miscibility of a 60–40 poly(styrene‐co‐acrylonitrile) with poly(methyl‐methacrylate) (PSAN/PMMA) blend. Thin disks, containing 60% w/w PSAN, are thermoformed from blend pellets made by mixing PSAN and PMMA granules in a co‐rotating, fully‐intermeshing twin‐screw extruder. These disks are sheared at constant shear rate in a cone‐and‐plate mechanical spectrometer at fixed temperatures within the quiescent two‐phase region. At the end of each shearing experiment the sample is quenched and its morphology investigated first visually for optical transparency (cloudiness being an indicator of a phase‐separated blend) and then using transmission electron microscopy (TEM). Results indicate that upon imposition of a shear rate as low as 0.1s −1 the 60–40 blend remains miscible even at temperatures up to 7K within the (quiescent) two‐phase region. These observations are in agreement with theoretical predictions of the phase diagram under shear, based on the concept of a modified Gibbs free energy of mixing. The TEM results concerning the morphology of the phase‐separated blends are also discussed.