White spirit permeation resistance of polyethylene,polyethylene/modified polyamide,and polyethylene/blends of modified polyamide and ethylene vinyl alcohol bottles

The main objective of this study was to investigate the barrier properties of polyethylene (PE), PE/modified polyamide (MPA), and PE/blends of modified polyamide and ethylene vinyl alcohol (MPAEVOH) bottles against white spirit permeation. After MPAEVOH barrier resins were blended with PE, the resistance of the PE/MPAEVOH bottles against white spirit permeation was significantly improved compared to the PE bottle. Surprisingly, with proper compositions of MPAEVOH resins, the white spirit permeation resistance of PE/MPAEVOH bottles at 40°C improved by more than 3000 times compared to the PE bottle, wherein the best permeation resistance (4200 times barrier improvement) of the PE/MPAEVOH bottles was found as the weight ratio of MPA : EVOH reached 4:1. These interesting permeation properties of PE/MPAEVOH bottles were investigated in terms of the barrier and free‐volume properties of the base resins and their corresponding morphologies in blow‐molded bottles. POLYM. ENG. SCI. 45:25–32, 2005. © 2004 Society of Plastics Engineers.     

Effects of processing conditions on the barrier properties of polyethylene (PE)/modified polyamide (MPA) and modified polyethylene (MPE)/polyamide (PA) blends

Different modified polyamide (MPA) and modified polyethylene (MPE) resins were prepared by reactive extrusion of different contents of a compatibilizer precursor (CP) with either polyamide (PA) or polyethylene (PE). The MPE and MPA resins were then blow‐molded with designed amounts of PA or PE resins to prepare four different sets of MPE/PA and PE/MPA bottles with the same CP, PA, and PE compositions. Somewhat surprisingly, the xylene permeation resistance of the MPE bottles is worse than that of the base PE bottle and decreases consistently as MPE contains more CP. In contrast, the MPE/PA and PE/MPA bottles exhibit much better xylene permeation resistance than that of the base PE bottle, wherein the PE/MPA bottles show significantly better permeation resistance than that of the corresponding MPE/PA bottles prepared at the same blow‐molding conditions. On the other hand, it is worth noting that the xylene permeation rate of each of the MPE/PA and PE/MPA bottles prepared at a fixed extrusion temperature reaches a minimum when prepared with an optimum screw speed near 400 rpm. Similarly, at a fixed screw speed, the highest permeation resistance of each PE/MPA bottle is always obtained when prepared at an optimum extrusion temperature of about 230^oC. However, the xylene permeation resistance of each MPE/PA bottle improves consistently when prepared at the higher extrusion temperatures used in this study. These interesting phenomena were investigated in terms of the morphology, thermal analysis of the PE/MPA and MPE/PA blends, the compatibility between PE (or MPE) and MPA (or PA), and the viscosity ratios of MPA (or PA) to PE (or MPE) during the blow‐molding process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1997–2008, 2000     

Gasoline Permeation Resistance of Containers of Polyethylene,Polyethylene/Modified Polyamide and Polyethylene/Blends of Modified Polyamide and Ethylene Vinyl Alcohol

An investigation of the gasoline permeation resistance of polyethylene (PE), polyethylene/modified polyamide (MPA), and polyethylene/blends of modified polyamide and ethylene vinyl alcohol (MPAEVOH) bottles is reported. The gasoline permeation resistance improves slightly after blending EVOH barrier resins in PE matrices during blow‐molding, wherein only broken and less demarcated EVOH laminas were found on the fracture surfaces of the PE/EVOH bottle. In contrast, much better permeation resistance and more clearly defined MPA and MPAEVOH laminas were found for PE/MPA and PE/MPAEVOH bottles, respectively. The gasoline barrier properties and MPAEVOH laminar structures of PE/MPAEVOH bottles improve and become more demarcated, respectively, as the MPA contents present in MPAEVOH resins increase. In fact, by using the proper composition, the gasoline permeation rate of PE/MPAEVOH bottles is about 450 and 3 times slower than that of the PE and PE/MPA bottles, respectively. These interesting gasoline barrier and morphological properties of PE, PE/MPA and PE/MPAEVOH were investigated in terms of melt shear viscosities and thermal properties of the base resins, and the chemical and physical amorphous phase structure present in their corresponding bottles.     

Barrier resistance of polyethylene,polyethylene/modified polyamide,and polyethylene/blends of modified polyamide and ethylene vinyl alcohol bottles against permeation of polar and nonpolar mixed solvents

The main objective of this study is to investigate the barrier properties and mechanisms of polyethylene (PE), PE/modified polyamide (MPA), and PE/blends of MPA and ethylene vinyl alcohol copolymer (MPAEVOH) bottles against permeation of polar/nonpolar (acetone/white spirit) mixed solvents. The mixed solvent permeation resistance improves dramatically after blending MPA and MPAEVOH barrier resins in PE matrices during blow molding. By using the proper MPAEVOH compositions, the white spirit permeation rate of PE/MPAEVOH bottles at 40°C can be about 145 times slower than that of the PE bottle specimen; however, it is still 2.5 times faster than that of the PE/MPA bottles. In contrast, the rate of polar acetone solvent permeation through the PE bottle is much slower than that of white spirit and only slightly faster than that through the PE/MPA and PE/MPAEVOH bottle specimens. In contrast, the permeation rates of acetone/white spirit mixed solvents into PE/MPA bottles are at least 20–60 times faster than the summation permeation rates calculated using the simple mixing rule when the acetone contents in the mixed solvents are between 10 and 70 wt %. It is somewhat interesting that, after blending the proper amounts of EVOH in MPA, the mixed solvent permeation rates of PE/MPAEVOH bottles are dramatically reduced and are very close to the summation permeation rates calculated using the simple mixing rule when the acetone contents are in the particular “window” range. These interesting barrier properties of PE/MPA and PE/MPAEVOH bottle specimens were investigated in terms of the free volumes, barrier properties, molecular interactions in the amorphous phases of the barrier resins, and their resulting morphological structures that present in their corresponding bottles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1333–1344, 2005     

Paint Solvent Permeation Resistance of Polyethylene,Polyethylene/Polyamide and Polyethylene/Modified Polyamide Bottles

The main objective of this study is to investigate the barrier mechanisms and properties of polyethylene, polyethylene (PE)/polyamide (PA) and polyethylene/modified polyamide (MPA) bottles against paint solvent permeation. In addition to the paint mixed solvent, the barrier properties of these bottles against the permeation of pure main solvents contained in the paint mixed solvent were investigated to understand the permeation mechanisms of the paint solvents. The paint solvent permeation resistance improves dramatically after blending PA and MPA barrier resins in PE matrices during blow‐molding. In fact, by using proper compositions, the white spirit permeation rates of PE/MPA and PE/PA bottles at 40°C are about 360 and 50 times slower than that of the PE bottle, respectively. Further investigations showed that, after blending the MPA and PA barrier resins in PE matrices, the hydrocarbon solvents present in the white spirit were nearly blocked without permeation during the permeation tests, i. e., PE/MPA bottles inhibited the permeation of hydrocarbon solvents more successfully than PE/PA bottles. In contrast, the rates of polar solvents with ketone, ether and alcohol functional groups permeating through the PE bottles are much slower than that of the white spirit and only slightly faster than those through the PE/PA and PE/MPA bottles. On the other hand, the paint mixed solvent permeation rates of PE bottles are approximately equal to the summation of permeation rates of the solvents present in mixed solvents calculated using a simple mixing rule. Somewhat surprising, the permeation rates of mixed solvents of PE/MPA bottles are dramatically faster than those calculated using a simple mixing rule, when the polar solvent contents are in a certain range.     

Oxygen permeation resistance of polyethylene,polyethylene/ethylene vinyl alcohol copolymer,polyethylene/modified ethylene vinyl alcohol copolymer,and polyethylene/modified polyamide–ethylene vinyl alcohol copolymer bottles

The oxygen permeation resistance of polyethylene (PE), polyethylene/ethylene vinyl alcohol copolymer (PE/EVOH), polyethylene/modified ethylene vinyl alcohol copolymer (PE/MEVOH), and polyethylene/modified polyamide–ethylene vinyl alcohol copolymer (PE/MPAEVOH) bottles was investigated. The oxygen permeation resistance improved significantly after the blending of ethylene vinyl alcohol copolymer (EVOH) barrier resins in PE matrices during blow molding; less demarcated EVOH laminas were found on the fracture surfaces of the PE/EVOH bottles. Surprisingly, the oxygen permeation resistance of the PE/MEVOH bottles decreased significantly, although more clearly defined modified ethylene vinyl alcohol copolymer (MEVOH) laminas were found for the PE/MEVOH bottles as the compatibilizer precursor contents present in the MEVOH resins increased. In contrast, after the blending of modified polyamide (MPA) in EVOH resins, more demarcated modified polyamide–ethylene vinyl alcohol copolymer (MPAEVOH) laminar structures were observed in the PE/MPAEVOH bottles as the MPA contents present in the MPAEVOH resins increased. In fact, with proper MPAEVOH compositions, the oxygen permeation resistance of the PE/MPAEVOH bottles was even better than that of the PE/EVOH bottles. These interesting oxygen barrier and morphological properties of the PE, PE/EVOH, PE/MEVOH, and PE/MPAEVOH bottles were investigated in terms of the free volumes, barrier properties, and molecular interactions in the amorphous‐phase structures of the barrier resins present in their corresponding bottles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2528–2537, 2004     

Permeation barrier properties of polyethylene/modified blends of polyamide and polyvinylalcohol containers against methanol/gasoline fuels

One commercial grade of polyamide and/or polyvinylalcohol resins were modified by a compatibilizer precursor to make various compositions of modified polyamide (MPA) and/or modified blends of polyamide/polyvinylalcohol (MPAPVA) through reactive extrusion. Good methanol/gasoline fuel permeation resistance together with clearly defined MPAPVA and MPA laminar structures were found on containers blow‐molded from the blends of polyethylene PE/MPAPVA and PE/MPA, respectively. The compositions of MPAPVA and MPA resins were found to exhibit a significant influence on the methanol/gasoline fuel permeation resistance and morphology of PE/MPAPVA and PE/MPA containers, respectively. Possible mechanisms are proposed to explain these interesting phenomena. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2158–2169, 1999     

Polar and Non-Polar Solvent Permeation Resistance of Blow-Molded Bottles of Polyethylene/Blends of Modified Polyamide and Polyamide 6 Clay Nanocomposite

Investigations on white spirit and acetone permeation resistance of modified polyamide and nylon 6 clay (MPANYC) blends and their corresponding polyethylene/MPANYC bottles were reported in this study. The white spirit and acetone permeation resistance of MPANYC sheets improve consistently with increasing NYC contents present in MPANYC resins after blending nylon 6 clay (NYC) in modified polyamide (MPA) resins. However, the order of barrier improvement of the PE/MPANYC and PE/NYC bottle specimens is not corresponding to the order of barrier improvement of the MPANYC and/or NYC barrier resins added in PE. The blow-molded PE/NYC bottle specimen exhibits similarly worse white spirit and acetone solvent permeation resistance as the PE bottle specimen, wherein no clearly formed NYC laminas but only dispersed NYC droplets or agglomerates were found on the fracture surfaces of the PE/NYC bottles. However, after blending optimum compositions of MPANYC in PE, the PE/MPANYC bottles with demarcated MPANYC laminas exhibit significantly better white spirit and acetone permeation resistance than the PE/MPA bottle, wherein the white spirit and acetone permeation rates of the PE/MPA₈NYC₁ bottle are about 1.3 and 1.4 times slower than those of the PE/MPA bottle, respectively. In order to understand these interesting barrier properties of PE/MPANYC and PE/NYC bottles, rheological, thermal, wide angle X-ray diffraction and morphological properties of the base MPANYC and NYC resins and their corresponding morphology present in the blow-molded bottles were investigated.     

Permeation mechanisms of xylene in blow-molded bottles of pure polyethylene,polyethylene/polyamide and polyethylene/ modified polyamide blends

The hydrocarbon permeation mechanisms of polyethylene/ modified polyamide (PE/ MPA). PE/PA blends and pure PE, were investigated over a range of testing temperatures. In addition to the permeation resistance to xylene, the weight of xylene absorbed per gram of dry polymers (Sx) and the diffusion coefficient (D) of xylene in these bottles were determined. At each fixed testing temperature, the steady permeation rates (Ps) and D of xylene in PE/MPA bottles is significantly lower than those of pure PE bottles, and that of PE/PA bottles is slightly lower. This significantly improved permeation resistance of PE/MPA to xylene at each testing temperature is mainly attributed to the significantly reduced diffusion coefficient of xylene in PE/ MPA bottles, but not due to the slight change in the amount of xylene absorbed in these three bottles. The temperature dependence of steady permeation rates and diffusion coefficient of xylene in each bottle is very similar, and, in fact, some clear transition points were found on the plots of Ps and D versus testing temperatures for PE. PE/PA and PE/MPA bottles. These interesting behaviors along with the temperature dependence of Sx in each bottle were discussed and correlated with the free volume, molecular relaxation motions of these polymers and the vapor pressure of xylene at varying testing temperatures.     

Gasoline Permeation Resistance of Polypropylene, Polypropylene/Ethylene Vinyl Alcohol, Polypropylene/Modified Polyamide, and Polypropylene/Blends of Modified Polyamide and Ethylene Vinyl Alcohol Containers

An investigation of the gasoline permeation resistance of the as-blow-molded polypropylene, polypropylene/ethylene vinyl alcohol (PP/EVOH), polypropylene/modified polyamide (PP/MPA) and polypropylene/blends of modified polyamide and ethylene vinyl alcohol (PP/MPAEVOH) bottles is reported. The gasoline permeation resistance improves slightly after blending EVOH barrier resins in PP matrices during blow-molding, wherein only broken and less demarcated EVOH laminas were found on the fracture surfaces of the PP/EVOH bottle. In contrast, much better permeation resistance and more clearly defined MPA and MPAEVOH laminas were found for PP/MPA and PP/MPAEVOH bottles, respectively. The gasoline barrier properties and MPAEVOH laminar structures of PP/MPAEVOH bottles improve and become more demarcated, respectively, as the MPA contents present in MPAEVOH resin increase. In fact, by using the proper composition, the gasoline permeation rate of PP/MPAEVOH bottle is about 113 and 11 times slower than that of the as-blow-molded PP and PP/MPA bottles, respectively. In order to understand these interesting gasoline barrier and morphological properties descried above, the melt shear viscosities, thermal properties, wide-angle X-ray diffraction patterns and Fourier-transform infrared spectra of the base resins used in these bottle specimens were investigated.     

Effects of polyethylenes on the morphology,barrier, and impact properties of polyethylene/modified polyamide blends

An investigation of the influence of the melt shear viscosities of polyethylenes (PE) on the morphology, barrier, and impact properties of polyethylene/modified polyamide PE/MPA bottles is reported. The melt shear viscosities of polyethylenes exhibited a significant influence on the deformation and morphology of MPAs during the blow molding of polyethylene/modified polyamide (PE/MPA) blends. Some obscure MPA laminars were observed in PE/MPA bottles as the value of melt shear viscosity ratio of MPA to PE (VR) deviated significantly from the “optimum” range. In contrast, clear and elongated laminar structures of MPAs were found as the value of VR reached the “optimum” range. Similarly, the total impact energies (Ets) and permeation barrier properties of PE/MPA samples improved with the value of VR until it reached the “optimum” range, after which value Ets and permeation barrier properties of PE/MPA samples reduced significantly with further increasing VR. Possible mechanisms accounting for these interesting behaviors are presented in this study.     

Effects of composition of modified polyamide on barrier properties of polyethylene/modified polyamide blends

A systematic study on the effects of types and contents of compatibilizer precursors (CPs) on degrees of crystallinity (W_c), melt shear viscosities (η_s), and permeation barrier properties of modified polyamides (MPAs) and on their corresponding morphology and barrier properties of bottles blow-molded from polyethylene (PE)/MPA blends is reported. Two alkylcarboxyl-substituted polyolefins were selected as CPs to modify PA and to improve its permeation resistance to xylene by the “reactive extrusion” process. The barrier improvements of MPAs prepared in this study depend significantly on the type and content of CP present in the MPA. A maximum improvement in barrier properties of each MPA series samples were found as the contents of CP reached an “optimum” value. On the other hand, it is interesting to note that bottles blow-molded from PE/MPA series samples exhibited better barrier properties because the MPAs used were associated with better permeation resistance to xylene. The melt shear viscosities of MPAs were found to depend on the type of CP used and increase with increasing CP contents. In contrast, the W_c of MPAs decreased with increasing CP contents. Further analysis of the fracture surfaces of bottles blow-molded from PE/MPA blends also indicated that the morphology of MPA laminas depended on the type of CP present in the MPA, and these MPA laminar structures became clearer as the contents of CPs increased. Possible mechanisms accounting for the interesting behaviors described above are discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1531–1540, 1997     

Gasoline permeation behavior and mechanical properties of polyamide 6/nanoclay,polyamide 6/PE‐g‐maleic anhydride blend,and polyamide 6/PE‐g‐maleic anhydride/clay nanocomposite

In this article, polyamide 6 (PA6)/clay nanocomposites, PA6/polyethylene grafted maleic anhydride (PE‐g‐MA) blends, and PA6/PE‐g‐MA/clay nanocomposites were prepared and their gasoline permeation behavior and some mechanical properties were investigated. In PA6/clay nanocomposites, cloisite 30B was used as nanoparticles, with weight percentages of 1, 3, and 5. The blends of PA6/PE‐g‐MA were prepared with PE‐g‐MA weight percents of 10, 20, and 30. All samples were prepared via melt mixing technique using a twin screw extruder. The results showed that the lowest gasoline permeation occurred when using 3 wt % of nanoclay in PA6/clay nanocomposites, and 10 wt % of PE‐g‐MA in PA6/PE‐g‐MA blends. Therefore, a sample of PA6/PE‐g‐MA/clay nanocomposite containing 3 wt % of nanoclay and 10 wt % of PE‐g‐MA was prepared and its gasoline permeation behavior was investigated. The results showed that the permeation amount of PA6/PE‐g‐MA/nanoclay was 0.41 g m^?2 day^?1, while this value was 0.46 g m^?2 day^?1 for both of PA6/3wt % clay nanocomposite and PA6/10 wt % PE‐g‐MA blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40150.     

Permeability of oxygen and water vapor through polyethylene/polyamide films

Oxygen and water vapor permeability studies were carried out on binary polyethylene/polyamide immiscible blends incorporating three polyethylene resins (LDPE, LLDPE, and HDsPE), and three polyamide resins (PA-6, PA-6,6, and modified PA-6,6m). It was found that the incorporation of PA into PE reduces the oxygen permeability while water vapor permeability is increased. In the range of 0 to 30 weight percent of PA, the oxygen permeability of PE was reduced by a factor of 2.8 to 3.6. Maximum water vapor permeabilities increased: for HDPE by a factor of about 2.6 to 3.1 and for LDPE and LLDPE blends by about 1.6.     

Compatibilization of polyethylene/polyamide 6 blends with oxazoline‐functionalized polyethylene and styrene ethylene/butylene styrene copolymer (SEBS)

Study was made of the compatibilization of polyethylene/polyamide 6 (PE/PA6) blends with a ricinoloxazoline maleinate grafted polyethylene and styrene ethylene/butylene styrene copolymer. The blends were prepared in a twin‐screw midiextruder, and the specimens for mechanical tests were injection molded with a mini‐injection molding machine. The effect of compatibilizing on the mechanical properties and the morphology of the blends was studied. The toughness and ductility of the blends were substantially improved as a result of the compatibilization. Simultaneously, the strength and stiffness were slightly reduced. Morphological studies showed that the particle size was reduced and the adhesion of the dispersed phase to the matrix was improved by the compatibilization. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1443–1450, 1999     

Designing polyethylene terephthalate‐based barrier resins

We have studied the efficiencies of commercially available barrier resins used for food packaging and beverage bottle applications and compared them with resins made using copolymer and blending approaches. The effects of various copolymer related parameters that influence oxygen barrier performance and the underlying mechanisms for these effects in PET‐based copolymers and blends were investigated. Using these approaches, it is possible to make highly effective PET‐based copolymers for gas barrier applications. Blending of PET with phenolic and other organic materials shows equivalent barrier performance in PET copolymers having comonomer levels of <8‐mole %. Reduction in oxygen permeation rates results from the reduction or elimination of short range molecular motion of polyethylene terephthalate molecules. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Orientation and crystalline morphology of blow molded polyethylene bottles

A study was carried out of the development of orientation during processing of conventional blow molded bottles made from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). The level of molecular orientation was found to be relatively low in all of the polyethylene bottles examined; it increased with increasing inflation pressure and decreasing extrusion temperature. Pole figures for the HDPE bottles indicated a slight a-axis orientation toward the circumferential direction of the bottle. The b-axes, which correspond to the lamellar growth direction, tend to be parallel to the bottle thickness direction. A comparison was made of the structure developed in blow molded bottles and blown films. The results for both films and bottles indicate that crystallization during processing involves both an increase in level of molecular orientation and an increased tendency toward biaxiality. Based on pole figures and small angle X-ray scattering patterns, a morphological model for HDPE blow molded bottles is proposed.     

Flame retardance and mechanical properties of a polyamide 6/polyethylene/surface‐modified metal hydroxide ternary composite via a master‐batch method

Surface‐modified aluminum hydroxide and magnesium hydroxide mixtures (SAMHs) were filled with linear low‐density polyethylene (LLDPE) with a maleic anhydride grafted polyethylene (PE) compatibilizer to produce a SAMH master batch, which was then dispersed in polyamide 6 (PA6) to yield a PA6/PE/SAMH (50/20/30 by weight ratio) ternary composite. Through such a master‐batch method, an effective flame retardance UL94 V‐0 rating at a 3.2 mm thickness with a 33% limiting oxygen index was achieved. The flame‐retardance mechanism of the ternary composite was investigated by thermogravimetric analysis and scanning electron microscopy/energy dispersive X‐ray spectroscopy analysis. A cocontinuous PA6/PE polymer host and a preferential dispersion of SAMH particles in the matrix induced the formation of a compact flame‐resistant char layer and a high residue rate during burning; this resulted in the desired flame retardance of the ternary composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of compatibilizer precursors on the barrier properties and morphology of polyethylene/polyamide blends

Summary A systematic investigation on the effects of type of compatibilizer precursors (CP) upon the barrier properties and morphology of PE/PA blends was reported. Three alkyl carboxyl-substituted polyolefins were selected to modify PA in a twin screw extruder by reactive extrusion process. The barrier property of the modified PA (MPA) was better than pure PA, and the amount of barrier improvement of the blend of PE and MPA dependended significantly on the barrier property of the MPA prepared. The extent of mixing PE and MPA before blow-molding has a significant effect on its corresponding barrier properties. Further analysis of the fracture surfaces indicated that a more demarcated laminar structure of MPA dispersed in PE matrix is essential for better barrier properties of PE/MPA blends. It is not completely clear how the type of CP added affects the barrier properties of MPAs. However, it is suggested that long PA sequence with shorter grafted CP chain and high normalized grafting efficiency of MPA are essential for preparing a clear laminar structure of MPA, and a good barrier properties of PE/MPA blends.     

Blending and white spirit permeation properties of the blends of modified polyamide and ethylene vinyl alcohol with varying vinyl alcohol contents

The blending and white spirit permeation properties of the MPAEVOH blends of modified polyamide (MPA) and ethylene vinyl alcohol copolymer (EVOH) were systematically investigated in this study. Three types of EVOHs with varying vinyl alcohol contents were used to prepare the MPAEVOH resins by melt blending them with the MPA resin, respectively. The peak melting temperatures and percentage crystallinity (W_c) values of the EVOH specimens increase significantly as their vinyl alcohol contents increase. The X‐ray diffraction patterns of the melt‐crystallized EVOH crystals transform from monoclinic to orthorhombic lattice as their vinyl alcohol contents are equal to or less than 56 wt %. After blending EVOH in MPA resins, the main melting endotherms and characteristic X‐ray diffraction patterns of both monoclinic and orthorhombic lattices of EVOH crystals originally present in MPAEVOH specimens almost disappear completely, when the weight ratios of MPA to EVOH are equal to or greater than 4. The free‐volume properties and white spirit permeation rates of the EVOH specimens reduce significantly as their vinyl alcohol contents increase. A noticeable “negative deviation” was found on the plots of white spirit permeation rates, annihilation intensity (I₃), and/or fractional free‐volume (F_v) versus MPA contents as the MPA contents of each MPAEVOH sample series reach about 80 wt %. Possible reasons accounting for these interesting blending and barrier properties of MPAEVOH specimens are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1224–1233, 2006