Blending and barrier properties of blends of modified polyamide and ethylene vinyl alcohol copolymer

Abstract

AbstractThe blending and barrier properties of the MPAEVOH blends of modified polyamide (MPA) and ethylene vinyl alcohol copolymer (EVOH) were systematically investigated in this study. After blending MPA in EVOH resin, a noticeable “negative deviation” was found on the plot of the oxygen permeation rate versus MPA content when the MPA contents present in MPAEVOH resins reach about 80 wt %. The peak temperatures associated with the main melting endotherm of MPA and EVOH reduce significantly with increasing the EVOH and MPA contents present in MPAEVOH resins, respectively. The melting endotherm and X‐ray diffraction peak associated with EVOH crystal phases disappear gradually as the MPA contents present in MPAEVOH increase. In fact, the melting endotherm and X‐ray scattering peak corresponding to EVOH crystals almost disappear as the EVOH contents present in MPAEVOH specimens are less than 20 wt %. Further Fourier‐Transform Infrared (FT‐IR) investigations indicate that the strengths of intermolecular hydrogen bonds of MPAEVOH specimens reduce significantly as the MPA contents increase, wherein the self‐associated hydroxyl‐hydroxyl bonds within EVOH resins almost disappear as the EVOH contents reduce to be less than about 20 wt %. As expected, the average sizes of the free volume holes of MPAEVOH specimens increase significantly as the MPA contents increase. However, somewhat surprisingly, a clear negative deviation was found on the plot of the numbers and fractional free volumes of free volume holes against the MPA contents as the EVOH contents are close to about 20 wt %. The interesting barrier properties of the MPA, EVOH, and MPAEVOH specimens were investigated in terms of the free volume and intermolecular interaction properties in the amorphous phases of MPAEVOH specimens described above. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 511–521, 2005