Partially miscible EVOH/copolyamide-6/6.9 blends: The effect of stretchingon the structure

Binary blends of random copolymers, ethylene-vinyl-alcohol (EVOH) consistin g of 38 mol % ethylene and Copolyamide-6/6.9 with an approximate 1 : 1 como nomer ratio, were prepared via blown-film extrusion and uniaxial stretching . The anisotropy induced by the uniaxial deformation of the polymer blends was characterized by X-ray diffraction and birefringence measurements. The stretched films also were investigated via oxygen permeability. The results showed a sharp decrease in the apparent crystallite size throughout the en tire composition range in comparison to the blown films. However, the order perceived within the amorphous phase in the EVOH-rich blends increased (de crease in oxygen permeability), whereas in the copolyamide-rich blends, ori entation resulted in a decrease in the amorphous phase order (increase in p ermeability). Apparently, orientation destroyed the amorphous interpolymer complex. (C) 2000 John Wiley & Sons, Inc.