EVOH nanocomposite films with enhanced barrier properties under high humidity conditions

To improve the oxygen and water vapor barrier properties of ethylene vinyl alcohol, EVOH/EFG nanocomposite films under high humidity conditions, we successfully prepared highly exfoliated graphite (EFG) containing a monolayer or a few layers of graphene via rapid heating treatment and ultrasonication as confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), elemental analysis (EA), and nitrogen adsorption–desorption analysis. Six different EVOH/EFG nanocomposite films containing as‐prepared EFG were prepared via a solvent blend method and their physical and barrier properties at different relative humidities were investigated as a function of EFG content. Depending on the EFG content, oxygen transmission rate (OTR) decreased from 3.7 to 0.1 cc/m²/day at dry condition, and the difference in OTR between dry condition and humid condition decreased from 6.5 to 2.3 cc/m²/day. Barrier properties of the EVOH/EFG nanocomposite films were strongly dependent on their chemical structure and morphology. Crystallinity, tortuous path length, and hydrophobicity of EVOH/EFG nanocomposite films were enhanced by the addition of EFG. However, the thermal stability and glass transition temperature of the nanocomposite films were not improved by incorporation of EFG due to the weak interaction between EVOH and EFG. To maximize the performance of EVOH/EFG nanocomposite films, the compatibility of the polymer matrix and fillers needs to be improved. POLYM. COMPOS., 35:644–654, 2014. © 2013 Society of Plastics Engineers     

Preparation and characterization of poly(propylene carbonate)/exfoliated graphite nanocomposite films with improved thermal stability,mechanical properties and barrier properties

Relatively high aspect ratio exfoliated graphite (EFG) particles with an average size of 7.4 µm and a nanometer sized thickness of 30–50 nm were successfully prepared by thermal treatment at 1050 °C and subsequent ultrasonication for application as a filler to improve the physical properties of eco‐friendly poly(propylene carbonate) (PPC). A series of poly(propylene carbonate)/exfoliated graphite (PPC/EFG) nanocomposite films with different EFG contents were prepared via a solution blending method. The physical properties were strongly dependent upon the chemical and morphological structures originating from the differences in EFG composition. The morphological structures, thermal properties, mechanical properties and barrier properties of the nanocomposite films were investigated as a function of the EFG content. While all of the PPC/EFG nanocomposite films exhibited good dispersion of EFG to some extent, Fourier transform infrared and SEM results revealed that solution blending did not lead to strong interactions between PPC and EFG. As a result, poor dispersion occurred in composite films with a high EFG content. By loading EFG particles, the oxygen permeabilities, moisture permeabilities and water uptake at equilibrium decreased as the EFG content increased. Compared with pure PPC, PPC/EFG nanocomposite films have enhanced molecular ordering. Specifically, the 2% PPC/EFG composite film shows greater molecular ordering than the other composite films, which results in the highest mechanical strength. In future work, the compatibility and dispersion of the PPC matrix polymer and EFG filler particles should be increased by modifying the EFG surface or introducing additives. © 2013 Society of Chemical Industry     

Thermal,mechanical, and gas barrier properties of ethylene–vinyl alcohol copolymer‐based nanocomposites for food packaging films: Effects of nanoclay loading

For the application of single‐layer food packaging films with improved barrier properties, an attempt was made to prepare ethylene‐vinyl alcohol (EVOH) copolymer‐based nanocomposite films by incorporation of organically modified montmorillonite nanoclays via a two‐step mixing process and solvent cast method. The highly intercalated tactoids coexisted with exfoliated clay nanosheets, and the extent of intercalation and exfoliation depended significantly on the level of clay loadings, which were confirmed from both XRD measurements and TEM observations. It was revealed that the inclusion of nanoclay up to an appropriate level of content resulted in a remarkable enhancement in the thermal, mechanical (tensile strength/modulus), optical, and barrier properties of the prepared EVOH/clay nanocomposite films. However, excess clay loadings gave rise to a reduction in the tensile properties (strength/modulus/elongation) and optical transparency due to the formation of clay tactoids with a larger domain size. With the addition of only 3 wt % clay, the oxygen and water vapor barrier performances of the nanocomposite films were substantially improved by 59 and 90%, respectively, compared to the performances of the neat EVOH film. In addition, the presence of clay nanosheets in the EVOH matrix was found to significantly suppress the moisture‐derived deterioration in the oxygen barrier performance, implying the feasibility of applying the nanocomposite films to single‐layer food packaging films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40289.     

Limonene transport and mechanical properties of EVOH and nylon 6,6 films as influenced by RH

The transport properties of d‐limonene through ethylene vinyl alcohol copolymers (EVOH) and nylon 6,6 films as functions of relative humidity (RH) and temperature were studied. Permeation properties of these polymers were strongly influenced by temperature and RH. Compared to the EVOH films, the nylon 6,6 film had much greater limonene permeability. Mechanical property studies indicated that both the tensile modulus and yield strength of the EVOH films decreased with an increase in RH. The polymer changed from being stiff and brittle at low RH to being soft and ductile at high RH. In addition, ethylene content and orientation were found to affect the transport and mechanical properties of limonene through EVOH polymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1949–1957, 2001     

Permeation of oxygen and water vapor through EVOH films as influenced by relative humidity

The transport properties of oxygen and water vapor through EVOH films as functions of relative humidity (RH) and temperature were studied. The results of oxygen and water vapor permeation demonstrated that temperature and RH markedly affected barrier properties of these films. In general, the EVOH films had minimal oxygen and water vapor permeabilities at a low RH, attributed to the reduced mobility of the polymer resulting from strong interactions between small water molecules and the polymeric matrix at low RH. Beyond 75% RH, the permeabilities increased considerably. In addition, the barrier performance of the EVOH films was found to be dependent on their ethylene content and orientation. From the experimental data, semiempirical equations describing oxygen transmission rates (O₂TR) as functions of RH and temperature were developed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1866–1872, 2001     

Nanocomposites of ethylene vinyl alcohol copolymer with thermally resistant cellulose nanowhiskers by melt compounding (I): Morphology and thermal properties

In this study, ethylene‐vinyl alcohol copolymer (EVOH) nanocomposites were prepared by melt compounding both plant cellulose nanowhiskers (CNW) and bacterial cellulose nanowhiskers (BCNW) as nanofillers. Electrospinning and a “dissolution precipitation” method were used as strategies for the incorporation of CNW in EVOH before melt compounding with the aim of enhancing the degree of dispersion of the nanocrystals when compared with direct melt‐mixing of the freeze‐dried product with the polymer. As revealed by morphological characterization, the proposed preincorporation methods led to a significant improvement in the dispersion of the nanofiller in the final nanocomposite films. Furthermore, it was possible to incorporate concentrations as high as 4 wt % BCNW without causing significant agglomeration of the nanofiller, whereas increasing the CNW concentration up to 3 wt % induced agglomeration. Finally, DSC studies indicated that the crystalline content was significantly reduced when the incorporation method led to a poor dispersion of the nanocrystals, whereas high‐nanofiller dispersion resulted in thermal properties similar to those of the neat EVOH. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure and properties of starch/poly(ethylene-co-vinyl alcohol) blown films

Blends of native corn starch and poly(ethylene-co-vinyl alcohol) (EVOH), with starch: EVOH ratios of 1 : 1 (SE-50) and 2 : 1 (SE-67A, SE-67B), were processed into blown films. SE-67A had a higher glycerol and water content and was processed at 5°C higher than was SE-67B. The films were conditioned to various moisture contents by equilibrating at a constant relative humidity and by oven drying at 41°C. Equilibrium moisture content, which ranged from 2 to 11%, increased with increasing starch content at a given relative humidity. Mechanical properties depended strongly on starch and moisture content as well as on processing history. The extension to break of SE-50 was only about one-third that of EVOH, while that of the 2 : 1 blends was even lower. SE-67A exhibited a higher extension to break, lower tensile strength and modulus, and greater moisture sensitivity than those of SE-67B. Differential scanning calorimetry and dynamic mechanical analysis revealed evidence of interactions between starch and EVOH, probably indicative of extensive intermixing but not necessarily miscibility. Scanning electron micrographs of fracture surfaces revealed extensive differences in texture with microcracking in SE-50 and SE-67A. The combination of the analytical results provide a basis for explaining many aspects of the mechanical behavior including the marked difference in properties between SE-67A and SE-67B. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2613–2622, 1997     

The synthesis and characteristics of sodium alginate/graphene oxide composite films crosslinked with multivalent cations

Association of a method of the incorporation of graphene oxide (GO) into sodium alginate (Na‐alg) polymer matrix with a method of the use multivalent cations crosslinker was put forward to synthesize novel Na‐alg/GO nanocomposite films. The structures, morphologies, and the properties of Na‐alg/GO films were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), thermogravimetric analysis (TGA), and tensile tests. The results revealed that the interlayer distance of GO sheets increased from 0.83 nm to 1.08 nm after assembling with Na‐alg, and Na‐alg inserted into GO layers crosslinking with multivalent cations increased the interlayer distance further. Ionic crosslinking significantly enhanced thermal and mechanical properties of Na‐alg/GO nanocomposite films. In particular, Fe³⁺ led to Na‐alg/GO nanocomposite films of significantly higher tensile strength and modulus than Ca²⁺ and Ba²⁺. The excellent thermal and mechanical properties of these novel Na‐alg/GO nanocomposite films may open up applications for Na‐alg films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43616.     

Aging Studies on Food Packaging Films Containing β-Cyclodextrin-Grafted TiO2 Nanoparticles

Polymeric materials, such as polyvinyl alcohol (PVA) and ethylene–PVA copolymers (EVOH) are widely used in the food sector as packaging materials because of their excellent properties. TiO₂ nanoparticles (NPs) show photocatalytic activity; when added to the aforementioned polymers, on the one hand, they are expected to provide bactericidal capacity, whereas on the other hand, they could favor nanocomposite degradation. These types of nanoparticles can be derivatized with cyclodextrin macromolecules (CDs), which can act as food preservative carriers, increasing the packaging food protective properties. In this work, films containing β-Cyclodextrin (βCD)-grafted TiO₂ nanoparticles and PVA or EVOH were prepared. Regarding the photocatalytic activity of the nanoparticles and the possible environmental protection, accelerated aging tests for PVA, EVOH, and their composites with cyclodextrin-grafted TiO₂ nanoparticle (NP) films were performed by two methods, namely, stability chamber experiments at different conditions of temperature and relative humidity and UV light irradiation at different intensities. After analyzing the systems color changes (CIELAB) and Fourier transform infrared spectroscopy (FTIR) spectra, it was observed that the film degradation became more evident when increasing the temperature (25–80 °C) and relative humidity percentage (28–80%). There was no significant influence of the presence of CDs during the degradation process. When irradiating the films with UV light, the largest color variation was observed in the nanocomposite films, as expected. Moreover, the color change was more relevant with increasing NP percentages (1–5%) due to the high photocatalytic activity of TiO₂. In addition, films were characterized by FTIR spectroscopy and variation in the signal intensities was observed, suggesting the increase of the material degradation in the presence of TiO₂ NPs.     

Effect of Type of Surfactants and Organoclay Loading on the Mechanical Properties of EVOH/Clay Nanocomposite Blown Films

EVOH/clay nanocomposite films were prepared by using four types of surfactants to treat surface of clay because the surfactants were expected to affect the degree of clay dispersion in the EVOH matrix, which would in turn affect the properties of film. The nanocomposite films that contained the single alkyl tail with two repeating units of oxyethylene surfactants or single alkyl tail surfactant showed higher tensile strength, tensile modulus and elongation at break than those with 15 repeating units of oxyethylene surfactants or those with double alkyl tail surfactant.     

Effect of clay type on dispersion and barrier properties of hydrophobically modified poly(vinyl alcohol)–bentonite nanocomposites

The oxygen and water vapor permeability at high relative humidity was studied for composite films formed by incorporation of three different bentonites (MMT) into an ethylene‐modified, water‐soluble poly(vinyl alcohol), EPVOH. The oxygen permeability decreased linearly with an increased addition of hydrophilic MMTs. X‐ray diffraction and Fourier transform infrared spectroscopy suggested a homogeneous distribution in the thickness direction with disordered and probably exfoliated structures for hydrophilic MMTs. In contrast, organophilic modified clay showed an intercalated structure with the clay preferentially located at the lower film surface, a combination which was however efficient in reducing the water vapor‐ and oxygen permeabilities at low addition levels. Composite films of EPVOH and Na⁺‐exchanged MMT resulted in high resistance to dissolution in water, which was ascribed to strong interactions between the components resulting from matching polarities. Annealing the films at 120°C resulted in enhanced resistance to water dissolution and a further reduction in oxygen permeability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42229.     

Oxygen barrier properties of polyketone/EVOH blend films and their resistance to moisture

Polyketone (PK) has excellent chemical and mechanical properties, but its use in food packaging is limited due to its oxygen barrier properties being insufficient for high-barrier film applications. To improve its oxygen barrier properties, PK has been blended with ethylene vinyl alcohol copolymer (EVOH), which is one of the highest oxygen barrier polymers in use today. The oxygen barrier properties under both dry and humid conditions, as well as the mechanical properties of PK/EVOH blend films were investigated in this study. These novel PK/EVOH blend films exhibited unusually low oxygen permeability values from 0.3 to 0.16 cc 20 μm m⁻² day⁻¹ atm⁻¹ with increasing EVOH content from 30 to 70 wt%, which are even lower than those of the ideal laminar model that expresses the theoretical minimum permeability values attainable for blended barrier films. These high oxygen barrier properties of PK/EVOH blend films can conceivably be attributed to the combination of two dominant effects: a tortuous diffusion path through the EVOH domains in the PK matrix and hydrogen bonding interactions between PK and EVOH. Furthermore, in high-humidity environments with retorting, the PK/EVOH blend films exhibited superior resistance to moisture over EVOH. Immediately after the retorting test, the oxygen permeability of the high-barrier PK/EVOH blend films with an EVOH content of 30–40 wt% increased by less than 3× the pre-retorting value, as opposed to 74× for EVOH. In addition, PK/EVOH blend films displayed superior stretching characteristics, with a breaking strain of over 300%, which are valuable for flexible packaging applications.     

Preparation and characterization of polynorbornene/sepiolite hybrid nanocomposite films

Polynorbornene/sepiolite hybrid nanocomposite films were prepared using polynorbornene dicarboximide and modified sepiolite with 3‐ aminopropyltriethoxysilane (3‐APTES). Exo‐N‐(3,5‐dichlorophenylnorbornene)‐5,6‐dicarboxyimide (monomer) and their copolymers were synthesized via ring‐opening polymerization using ruthenium catalysts. Subsequently, the surface‐modified sepiolite by 3‐APTES was mixed with the polynorbornene copolymers to prepare hybrid nanocomposite films. The modified sepiolite particles were well dispersed in N,N‐dimethylacetamide and distributed randomly throughout the polynorbornene matrix in the hybrid films, which enhanced the dimensional stability and mechanical and oxygen barrier properties of the polynorbornene/sepiolite hybrid nanocomposite films. © 2014 Society of Chemical Industry     

Preparation of poly(styrene‐co‐butyl acrylate)/montmorillonite nanocomposite by emulsion polymerization: Characterization and nanoscratch behavior

Organic–inorganic hybrid poly(styrene‐co‐butyl acrylate)/organically modified montmorillonite (PSBA/organo‐MMT) latex particles have been prepared by in situ emulsion polymerization. The effects of modifier variety and the level of organo‐MMT have been investigated on the basis of the characteristics and mechanical properties of the resulting hybrid emulsion polymers. Although the more hydrophilic intercalated organic modifiers increased the latex particle size, the hydrophobic ones decreased the particle size. A more heterogeneous copolymer chain intercalation was seen by widespread XRD reflection as the organo‐MMT (organoclay) level increases. The tapping mode atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to determine the dispersion state of organoclay particles inside the nanocomposite copolymer films. Dynamic mechanical thermal analysis (DMTA) showed that adding the organoclay to the copolymer decreased the maximum loss tangent (tanδ) value and caused the shift to a lower temperature. Interestingly, the incorporation of organoclay decreased the glass storage modulus of the copolymer, while increased the rubbery storage modulus to some extent. In addition, a standard indenter for the nanoscratching of copolymer nanocomposite films was used under low applied loads of 150 and 250 μN. The nanoscratch results showed that incorporation of a 3 wt % hydrophobic organoclay, e.g., Closite15A, in the copolymer matrix enhanced considerably the near‐surface hardness and grooving resistance of the nanocomposite film at room temperature. In fact, copolymer nanocomposite films with higher near‐surface hardness and tanδ curve broadening exhibited more nanoscratch resistance through a specific variety of viscoelastic deformation, which did not create a bigger groove. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Hydrophobic properties of ethylene–vinyl alcohol copolymer treated with plasma source ion implantation

The industrial use of ethylene–vinyl alcohol copolymer (EVOH) film is limited because it is easily degraded by moisture. The plasma source ion implantation (PSII) technique with CF₄ or CH₄ gas was used for the EVOH film to improve the surface hydrophobic properties. Variables examined in implantation were ion energy (0–10 keV), treatment time (5 s–5 min), and ion species. The hydrophobic properties of EVOH films were greatly enhanced after a CF₄ PSII treatment, as evidenced by an increased contact angle from 66° to above 100° at ‐5 keV, and remained relatively unchanged during the period of 28 days. X‐ray photoelectron spectroscopy, atomic force microscopy, and O₂ permeability were used to characterize the surface properties of EVOH films treated with PSII. The improved hydrophobic properties were closely related to the formation of fluorine‐containing functional groups such as CF, CF_2, and CF₃ on the modified surface. The percentage distribution of carbon functional groups supports the role of CF₂ and CF₃ groups in surface modification. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2069–2075, 2004     

Effect of interfacial attraction on intercalation in polymer/clay nanocomposites

In order to examine the adhesive behavior of a polar polymer between hydrophilic clay layers, the so‐called glue effect, a clay intercalation by an ethylene–vinyl alcohol (EVOH) copolymer, which was capable of strong hydrogen bonding with the silicate surface of clay, was prepared by the melt intercalation technique and compared with a clay nanocomposite containing styrene–acrylonitrile (SAN) copolymer of less polar interaction energy in terms of the morphology and mechanical properties. Although initial penetration of the guest polymer into the gallery of the host clay occurred more rapidly for EVOH because of its strong hydrophilic nature, the dissociation of clay nanoplatelets was better developed for SAN with less polar interaction with clay, well evidencing the fact that the glue effect effectively affects the intercalation behavior of polymer/clay nanocomposites. However, the mechanical properties of the EVOH/clay nanocomposite were superior to those of SAN/clay nanocomposites. Although dissociation of respective silicate layers was poor for EVOH/clay nanocomposites, strong attractive energy stabilizes the interface between inorganic nanoparticles and the polymer matrix much more effectively, resulting in higher mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2749–2753, 2006     

Development of bacterial cellulose nanowhiskers reinforced EVOH composites by electrospinning

In the current study, hybrid electrospun ethylene vinyl alcohol (EVOH) fibers reinforced with bacterial cellulose nanowhiskers (BCNW) were developed and characterized. Additionally, electrospinning was suggested as a method for the incorporation of well‐dispersed BCNW into an EVOH matrix by melt compounding. With the aim of maximizing the BCNW's loading in the electrospun fibers, an optimized method was applied for generating fibers from solutions containing up to 40 wt % BCNW. As demonstrated by FTIR spectroscopy, it was possible to incorporate BCNW concentrations up to ～ 24 wt %, although a complete incorporation of the nanofiller into the fibers was only achieved with solutions containing up to 20 wt % of the filler, DSC analyses suggested that the incorporation of the nanofiller reduced the crystallinity of the as‐obtained EVOH fibers and produced an increase in the glass transition temperature of these during the second heating run. Thermogravimetric analyses showed that even though EVOH protects the nanowhiskers from thermal degradation, the electrospun hybrid fibers present a relatively lower thermal stability than the pure EVOH fibers. FTIR analyses of the samples subjected to different thermal treatments confirmed that the stiffening effect observed by DSC only occurs after melting of the EVOH phase and is cooperative with a partial acid chemical development in the BCNW, which promotes strong chemical interactions between the polymeric matrix and the nanofiller. Finally, the hybrid electrospun fibers were incorporated into pure EVOH by melt compounding to produce composite films. This methodology showed higher stability and dispersion of the BCNW than direct addition of the freeze‐dried nanofiller to EVOH. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Bio‐hybrid nanocomposite coatings from sonicated chitosan and nanoclay

Nanocomposite films and coatings with improved properties were produced from ultrasonic dispersed chitosan and hydrophilic bentonite nanoclay. Bio‐hybrid coatings were applied onto argon–plasma‐activated LDPE coated paper. The intercalation of chitosan in the silicate layers was confirmed by the decrease of diffraction angles as the chitosan/nanoclay ratio increased. Nanocomposite films and multilayer coatings had improved barrier properties against oxygen, water vapor, grease, and UV‐light transmission. Oxygen transmission was significantly reduced under all humidity conditions. In dry conditions, over 99% reduction and at 80% relative humidity almost 75% reduction in oxygen transmission rates was obtained. Hydrophilic chitosan was lacking the capability of preventing water vapor transmission, thus total barrier effect of nanoclay containing films was not more than 15% as compared with pure chitosan. Because to very thin coatings (≤1 μm), nanoclay containing chitosan did not have antimicrobial activity against test strains. All coating raw materials were “generally recognized as safe” (GRAS) and the calculated total migration was in all cases ≤6 mg/dm², thus the coatings met the requirements set by the packaging legislation. Processing of the developed bio‐hybrid nanocomposite coated materials was safe as the amounts of released particles under rubbing conditions were comparable with the particle concentrations in a normal office environment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Evaluation of starch‐PE multilayers: Processing and properties

Adhesion tests performed on various plasticized starch‐polyethylene multi‐layer systems led to the selection of a suitable combination of polymers compatible with the starch‐based layer. The compatibility of starch and polyethylene was better achieved through maleic anhydride functionalized polyethylene (PEg) than chemically modifying starch. The PEg method proved efficient provided that the water content, and the plasticizer nature and contents of the starch layer were carefully chosen. Computed shear viscosity allowed us to select a suitable botanical origin of starch such that the interfacial instabilities of the coextrusion process were minimized. The use of a multilayer structure (PE/PEg/starch/PEg/PE) improved gas barrier properties at high relative humidity. The higher quantity of water sorbed by thermoplastic starch (as compared to EVOH) coupled with starch's specific water sorption isotherm lengthened the water equilibration time in the hydrophilic inner layer significantly. As a result the gas barrier properties of the starch based multiplayer systems were enhanced as compared to existing commercial multiplayer systems (PE/PEg/EVOH/PEg/PE). This specific “water‐buffering property” of the starch inner layer should prove useful in packaging applications of perishables with extended shelf life in environments of varying relative humidity. Polym. Eng. Sci. 45:217–224, 2005. © 2005 Society of Plastics Engineers.     

PE—LD吸氧薄膜的研制

采用铁系脱氧剂、乙烯-乙烯醇共聚物(EVOH)、相容剂和PE-LD,通过双螺杆挤出机制备吸氧母料,将其与适量PE-LD混合经单螺杆挤出机吹塑成吸氧薄膜。考察了吸氧薄膜配方、温度和湿度对吸氧性能的影响。结果表明,随着铁系脱氧剂和EVOH含量的增加、环境温度的提高以及环境湿度的变大,薄膜吸氧量会随之增加;随着薄膜厚度的增加,薄膜吸氧量减少。