STUDY OF BLENDS OF NYLON-6 WITH EVOH AND CARBOXYL-MODIFIED EVOH AND APRELIMINARY APPROACH TO FILMS FOR PACKAGING APPLICATIONS

Blends of nylon 6 (Ny6) with ethylene-co-vinyl alcohol (EVOH) and EVOH modified with the introduction of carboxyl groups (EVOH-COOH) have be en studied by Fourier transform infrared spectroscopy, scanning electr on microscopy, differential scanning calorimetry, and dynamic-mechanic al thermal analysis. The thermal and thermomechanical analyses of the blends show that the melting, crystallization, and relaxational behavi or are affected by the blend composition and the presence of carboxyl groups on the EVOH chains. Nevertheless, microscopic and thermal inves tigations demonstrate the biphasic nature of the two-blend systems. Se lective solvent extraction of the EVOH or EVOH-COOH phase in their ble nds and Fourier transform infrared analysis of the residual products i ndicates the occurrence of ionic linkages between the amino groups of the polyamide and the carboxyl groups of the modified EVOH, whereas sp ecific interactions are evidenced for Ny6/EVOH blends. Tests performed on extruded Ny6/EVOH films show that the addition of EVOH effectively reduces the gas permeability of Nylon, whereas the addition of small amounts of EVOH-COOH helps to control and stabilize melt theology. (C) 1998 John Wiley & Sons, Inc.