Phase homogenization of mixtures of poly( m-xylene adipamide) and nylon 6 by interchange reactions

Abstract

Melt blends of poly( m-xylene adipamide) and nylon 6 prepared by extrusion at 260°C have two glass transitions and are opaque, whereas similar preparation at 290°C yields transparent melts and materials with a single glass transition. This phase homogenization has been shown by thermal, dynamic mechanical, and nuclear magnetic resonance analyses to be the result of interchange reactions. A single phase develops after as few as five interchange reactions per molecule. This segmented block structure explains the high level of crystallinity that is retained after phase homogenization. Such behaviour is possible when the unreacted components have an unfavourable but small interaction energy density, i.e. near miscibility, as argued using thermodynamic theories. Retention of crystallinity is useful for certain property considerations.