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a) b - École Polytechnique de Montréal

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CHAPTER 6 - MORPHOLOGICAL STATES FOR A TERNARY POLYMER<br />

6.1 Abstract<br />

BLEND DEMONSTRATING COMPLETE WETTING<br />

For the most part, ternary polymer blends <strong>de</strong>monstrate complete wetting behavior. Conceptually,<br />

this is the state where one of the components will always tend to completely separate the other<br />

two and from a thermodynamic viewpoint is <strong>de</strong>scribed as the case where two of the three<br />

possible binary spreading coefficients are negative and the other is positive, as <strong>de</strong>fined by<br />

Harkins spreading theory. This work examines the complete range of morphological states<br />

possible for such a system over the entire ternary composition diagram as prepared by melt<br />

mixing. A ternary polymer blend comprised of high-<strong>de</strong>nsity polyethylene(HDPE),<br />

polystyrene(PS), and poly(methyl methacrylate)(PMMA) is selected as a mo<strong>de</strong>l system<br />

<strong>de</strong>monstrating complete wetting and four sub-categories of morphologies can be i<strong>de</strong>ntified<br />

including: a) matrix/core-shell dispersed phase; b) tri-continuous; c) matrix/two separate<br />

dispersed phases;, and d) bi-continuous/dispersed phase morphologies. Electron microscopy as<br />

well as a technique based on the combination of focused ion beam irradiation and atomic force<br />

microscopy are used to clearly illustrate and i<strong>de</strong>ntify the various phases. Solvent<br />

extraction/gravimetry is used to examine the extent of continuity of the systems so as to<br />

effectively i<strong>de</strong>ntify regions of high continuity. Triangular compositional diagrams are used to<br />

distinguish these various morphological regions and the results are interpreted in light of the<br />

interfacial tension of the various binary combinations and their subsequent spreading<br />

coefficients. The effect of the molecular weight and of viscosity ratio on the phase size of the<br />

various structures is also consi<strong>de</strong>red.<br />

Keywords: ternary polymer blend, double-percolated morphology, tri-continuous, compositedroplet,<br />

co-continuous structure<br />

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