Effect of the acrylic acid content on miscibility and mechanical properties of mixtures of poly[ethylene-co(acrylic acid)] and poly(2-ethyl-2-oxazoline)

The miscibility behavior of blends of poly(2-ethyl-2-oxazoline) (PEOX) and poly[ethylene-co-(acrylic acid)] was studies as a function of the acrylic acid content with the help of differential scanning calorimetry (DSC), modulated DSC and dynamic mechanical thermal analysis (DMTA). Miscibility, ascertained by the existence of a single glass transition in the mixtures, is achieved only between the PEOX and the copolymers with a high acrytic acid content (20%). The other two polymer pairs are immiscible at all compositions. FTIR spectroscopy demonstrates that miscibility is enhanced by hydrogen bonding interactions between the amide groups of the PEOX and the carboxylic groups of the acrylic acid units in the copolymer. Tensile stress and compressive creep tests reveal that the 20 and the 40 wt.-% PEOX blends exhibit synergistic mechanical properties, i.e., better ultimate properties, smaller Young's moduli and higher creep compliances. © Wiley-VCH Verlag GmbH, 2001.