Phase behavior of UCST blends: Effects of pristine nanoclay as an effective or ineffective compatibilizer

Abstract

The effects of unmodified nanoclay (natural montmorillonite) on the miscibility, phase behavior and phase separation kinetics of polyethylene (PE)/ethylene vinyl acetate copolymer (EVA) blends have been investigated. Depending on the blend composition, it was observed that the intercalated pristine nanoclay influences the biphasic morphology either as an effective compatibilizer or just as an ineffectual modifier. In spite of the presence of micrometer-sized agglomerated tactoids, natural nanoclay can play a thermodynamic role in reducing the interfacial tension of polymer components. The addition of clay nanoparticles was found to change the phase diagram slightly and diminishes the composition dependency of the binodal temperatures. Moreover, it was observed that a small amount of unmodified layered silicate slows down the phase separation process considerably and enhances the solubility of each polymer in the domains of its counterpart. The findings of this study verify that even poorly dispersed nanoclay with high surface tension can act as a conventional compatibilizer and change the immiscible PE/EVA blends to the partially miscible ones.

Keywords

• Polymer blends and alloys
• Miscibility
• Nanocomposites
• Rheology
• Phase separation