Morphology and infrared spectroscopy of strongly interacting polymer blends: EVOH/copolyamide-6/6.9

The presence of aliphatic hydroxyl groups in poly(ethylene-co-vinylalcohol) (EVOH) suggests that these copolymers have the potential of forming miscible blends, within certain composition ranges, with a variety of polymers containing complementary functional groups. Hydrogen bonding in EVOH involves a wide variety of inter- and intramolecular species and plays an important role in the phase behavior of EVOH blends. Polymer blends of two random copolymers, EVOH with different ethylene contents and copolyamide-6/6.9 (COPA) at an approximately 1:1 comonomer ratio, were investigated using Fourier transform infrared (FTIR), near-IR, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) methods. The blends were found to be partially miscible due to intermolecular hydrogen bonding between the OH group of the EVOH and the amide group of the copolyamide. The EVOH-rich blends exhibit much lower;miscibility compared with the copolyamide-rich blends.