Chemistry

A Better Blend

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Science  30 Jun 2006:
Vol. 312, Issue 5782, pp. 1849
DOI: 10.1126/science.312.5782.1849c

The optimization of material properties in preparing mixtures of two distinct polymers is often impeded by the tendency of the blends toward phase separation. One possible solution is the incorporation of a third component to stabilize the interfaces. Clays can be useful for this purpose because they consist of platelets that can intercalate or flake apart (exfoliate), offering a large surface area for interaction.

In this vein, Si et al. explored the impact on a variety of polymer blends of adding montmorillonite clays modified with organic surfactant. They found first that the organoclay mixed favorably with poly(methylmethacrylate) (PMMA), polycarbonate (PC), and poly(styrene-co-acrylonitrile) (SAN), but not with polystyrene (PS). Nonetheless, in PS/PMMA blends, the clay platelets localized at the interfaces and influenced domain morphology. In PC/SAN blends, the degree of dispersion between the polymers increased with increasing organoclay concentration, with a bicontinuous morphology observed for concentrations above 5%. The added surfactant proved crucial, because unmodified clays did not aggregate at the interfaces but instead dissolved in one of the polymer components. Similar observations across a range of additional polymer mixtures, including a slurry of styrofoam and scrap plastic, highlighted the potential utility of such clays for recycling applications, which require the blending of incoming waste streams that comprise a wide variety of polymeric materials. — MSL

Macromolecules 39, 10.1021/ma060125+ (2006).

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