Efficient approach to high barrier packaging using microfibrillar cellulose and shellac

This paper presents an investigation on the enhancement of the barrier properties of paperboard and paper. Microfibrillar cellulose (MFC) and shellac were deposited on the fibre based substrates using a bar coater or a spray coating technique. The air, oxygen and water vapour permeability properties were measured to quantify the barrier effect of the applied coatings. In addition, the mechanical properties were determined and image analysis of the structure was performed to examine the coating adhesion. The air permeance of the paperboard and papers was substantially decreased with a multilayer coating of MFC and shellac. Furthermore, for the MFC and shellac coated papers, the oxygen transmission rate decreased several logarithmic units and the water vapour transmission rate reached values considered as high barrier in food packaging (6.5 g/m² 24 h). The analysis of mechanical and morphological properties indicated good adhesion between the coating and the base substrate.     

Properties of nitrocellulose‐coated and polyethylene‐laminated chitosan and whey films

Chitosan (chitosan acetic acid salt) and whey (65% protein) films were coated with a nitrocellulose lacquer or laminated with polyethylene to enhance their water resistance and gas barrier properties in humid environments. The barrier properties were measured by the Cobb₆₀ test and water‐vapor (100% relative humidity) transmission and oxygen (90% relative humidity) permeability tests. Mechanical properties were obtained with tensile tests. Packaging properties were studied with crease and folding tests. The Cobb₆₀ test revealed that the coated films were resistant to liquid water, at least for a short exposure time, if the coating thickness was at least 10–17 μm. Water‐vapor transmission rates comparable to those of polyethylene‐laminated films were obtained for coated chitosan at a coating thickness of 5–7 μm. The coated films possessed low oxygen permeability despite the high humidity. Coated films dried for 3 weeks showed oxygen permeabilities at 90% relative humidity that were similar to values for dry ethylene‐co‐vinyl alcohol at 0% relative humidity. The lacquer partly penetrated the whey films, and this led to excellent adhesion but poor lacquer toughness. The lacquer coating on chitosan was tougher, and it was possible to fold these films 90° without the coating fracturing if the coating thickness was small. The coated whey films were readily creasable. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 985–992, 2001     

Comparison of hydroxypropyl and carboxymethyl guar for the preparation of nanocellulose composite films

The gas barrier and mechanical properties are crucial parameters for packaging materials, and they are highly correlated to the molecular interactions in the polymer matrix. To improve these properties of TEMPO-oxidized cellulose nanofibers (TOCNs) composite films, we studied the effect using hydroxypropyl guar (HPG) or carboxymethyl guar (CMG) in the preparation of TOCN composite films, which were made by following the solution-casting method. The subsequent film characterizations were carried out by UV–Vis spectra, scanning electron microscopy, oxygen and water vapor permeability measurements, tensile and thermogravimetric analyses. SEM results showed that CMG-based films had denser structures than their HPG counterparts. Moreover, the improved hydrogen bonding of the CMG-based films was partially responsible for the improved gas barrier performance, tensile strength and thermal stability. These results support the conclusion that CMG had advantages over HPG when used in the preparation of TOCNs packaging composite films.     

Microfibrillated cellulose (MFC): pullulan bionanocomposite films

The aim of this work was to develop and characterize microfibrillated cellulose (MFC)/pullulan bionanocomposites. Fourier transform infrared spectroscopy suggested that the affinity between the two polymers resulted in new hydrogen bonding of the nanocomposite materials compared to pristine pullulan. At the same time, an increase in crystallinity was observed proportional to the amount of MFC used, as shown by the X-ray analyses. Accordingly, final films showed improved mechanical properties proportionally to the filler loading, with impressive elastic modulus and tensile strength of ~4.50 GPa and ~60 MPa, respectively, for the sample containing 10 % MFC. However, as demonstrated by the moisture sorption isotherms, the addition of MFC did not help reduce the amount of water adsorbed by the samples. In addition, the oxygen and water vapor permeability data clearly showed that final films still suffered high relative humidity values, whereas their barrier performance toward oxygen was excellent under dry conditions, with O₂ permeability coefficients (P′O ₂) comparable with those of common high barrier films/coatings. Finally, while the nanocomposites in the form of films had high haze values (from 23 to 40 %), the same nanocomposites in the form of coatings were decidedly more transparent, which suggests that their use as thin layers could be more suitable when the “see-through” capability must be preserved, for example in food packaging applications.     

Composite films from spruce galactoglucomannans with microfibrillated spruce wood cellulose

Two future wood biorefinery products, spruce galactoglucomannans (GGM) and microfibrillated spruce wood cellulose (MFC), were mixed to form composite films. The films were plasticized with different amounts of glycerol, and the preparation of films was successful even with low glycerol contents. The film properties were studied using optical microscopy and scanning electron microscopy, x-ray diffraction, water sorption, dielectric analysis, moisture scanning dynamic mechanical analysis, and tensile testing. The addition of MFC clearly affected the properties of the films by decreasing the moisture uptake and increasing the relative humidity of softening of the films and by increasing the glass transition temperature, tensile strength, and Young’s modulus of the films. The effect of MFC addition on the tensile properties of films was emphasized at low glycerol contents. The addition of MFC did not affect the degree of crystallinity of GGM in the films, which was between 20 and 25%. MFC can be efficiently used as reinforcement of GGM films to form wood-based composite materials and to prepare GGM-based films and coatings with low plasticizer content.     

Gas-phase esterification of microfibrillated cellulose (MFC) films

The barrier properties of microfibrillated cellulose (MFC) films were improved by heterogeneous gas-phase esterification using various combinations of trifluoroacetic acid anhydride, acetic acid and acetic anhydride. The temperature, reagent ratio and reaction time were varied in the experimental design. The effects of two different purification procedures on the barrier properties of esterified MFC films were investigated. Washing with water did not affect the barrier properties compared to those of the films that were not washed, while the use of diethyl ether led to improved barrier properties as measured by the contact angle (CA) of water. The chemical composition of the modified films was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Alterations in hydrophobicity and oxygen permeability were evaluated using dynamic CA and oxygen transmission rate measurements, respectively.     

Ultrasound-assisted pullulan/montmorillonite bionanocomposite coating with high oxygen barrier properties

In this paper, the preparation and characterization of oxygen barrier pullulan sodium montmorillonite (Na(+)-MMT) nanocomposite coatings are presented for the first time. Full exfoliation of platelets during preparation of the coating water dispersions was mediated by ultrasonic treatment, which turned out to be a pivotal factor in the oxygen barrier performance of the final material even at high relative humidity (RH) conditions [oxygen permeability coefficients ~1.43 ± 0.39 and 258.05 ± 13.78 mL·μm·m(-2)·(24 h)(-1)·atm(-1) at 23 °C and 0% RH and 70% RH, respectively]. At the micro- and nanoscale, the reasons are discussed. The final morphology of the coatings revealed that clay lamellae were stacked on top of one another, probably due to the forced confinement of the platelets within the coating thickness after solvent evaporation. This was also confirmed by modeling the experimental oxygen permeability data with the well-known Nielsen and Cussler permeation theoretical models, which suggested a reasonable aspect ratio (α) of ~100. Electron microscopic analyses also disclosed a peculiar cell-like arrangement of the platelets. The stacking of the clay lamellae and the cell-like arrangement create the excellent oxygen barrier properties. Finally, we demonstrated that the slight haze increase in the bionanocomposite coating materials arising from the addition of the clays depends on the clay concentration but not so much on the sonication time, due to the balance of opposite effects after sonication (an increase in the number of scattering centers but a reduction in their size).     

基于荧光素的荧光纳米纤维的制备与表征

以电纺聚丙烯腈(PAN)纳米纤维为起始物, 经乙二胺改性后, 再利用Mannich反应将荧光素共价连接于PAN纳米纤维薄膜表面. 用荧光光谱、 扫描电镜和红外光谱进行了结构表征. 结果表明, 利用荧光素对静电纺丝薄膜表面进行修饰, 获得了很强的荧光信号, 证明了方法的可行性.     

Strength and barrier properties of MFC films

The preparation of microfibrillar cellulose (MFC) films by filtration on a polyamide filter cloth, in a dynamic sheet former and as a surface layer on base paper is described. Experimental evidence of the high tensile strength, density and elongation of films formed by MFC is given. Typically, a MFC film with basis weight 35 g/m² had tensile index 146 ± 18 Nm/g and elongation 8.6 ± 1.6%. The E modulus (17.5 ± 1.0 GPa) of a film composed of randomly oriented fibrils was comparable to values for cellulose fibres with a fibril angle of 50°. The strength of the films formed in the dynamic sheet former was comparable to the strength of the MFC films prepared by filtration. The use of MFC as surface layer (0–8% of total basis weight) on base paper increased the strength of the paper sheets significantly and reduced their air permeability dramatically. FEG-SEM images indicated that the MFC layer reduced sheet porosity, i.e. the dense structure formed by the fibrils resulted in superior barrier properties. Oxygen transmission rates (OTR) as low as 17 ml m⁻² day⁻¹ were obtained for films prepared from pure MFC. This result fulfils the requirements for oxygen transmission rate in modified atmosphere packaging.     

Controlled release and long-term antibacterial activity of chlorhexidine digluconate through the nanoporous network of microfibrillated cellulose

The recent study focusing on paper coated with microfibrillated cellulose (MFC) revealed the ability of such a structure to achieve a controlled release of molecules introduced into its nanoporous network. The present study examines this concept using a chlorhexidine digluconate-based (CHX) antibacterial solution. Various analyses were performed, optical microscopy, FE-SEM and AFM to underline the structure of the nanoporous MFC network. Release studies were conducted in an aqueous medium following two different protocols and antibacterial tests were done to evaluate the efficiency of the final materials obtained. MFC coating provided a slower and more progressive release of CHX. Indeed, papers impregnated with CHX were active for 18 days, whereas papers coated with CHX/MFC retained their antibacterial activity for 45 days. In parallel, similar tests were carried out using a model coating slurry, and although the rate of release of CHX was also slowed down, the quantities released were insufficient to confer any antibacterial activity. In conclusion, this study suggests that the use of MFC as a coating could be very promising since it allows a controlled and progressive release of molecules preserving long-term antibacterial activity.     

Multi-functional coating of cellulose nanocrystals for flexible packaging applications

In this paper, we systematically address the performance of cellulose nanocrystals (CNs) coated flexible food packaging films. Firstly, the morphology of CNs from cotton linters and homogeneity of its coating on different substrates were characterized by transmission electronic microscopy and atomic force microscopy. Then, the 1.5 μm thick CNs coating on polyethylene terephthalate (PET), oriented polypropylene, oriented polyamide (OPA), and cellophane films were characterized for their mechanical, optical, anti-fog, and barrier properties. CNs coating reduces the coefficient of friction while maintaining high transparency (~90 %) and low haze (3–4 %) values, and shows excellent anti-fog properties and remarkable oxygen barrier (oxygen permeability coefficient of CNs coating, P’O₂, 0.003 cm³ μm m^?2 24 h^?1 kPa^?1). In addition, the Gelbo flex test combined with oxygen permeance (PO₂) measurements and optical microscopy are firstly reported for evaluating the durability of coatings, revealing that the CNs coated PET and OPA provide the best performance among the investigated coated films. CNs are therefore considered to be a promising multi-functional coating for flexible food packaging.     

Characterization of Plasma-Polymerized 4-vinyl Pyridine with Silver Nanoparticles on Poly(ethylene terephthalate) Film for Anti-Microbial Properties

4-vinyl pyridine was polymerized on poly(ethylene terephthalate) (PET) film by using lower energy pulsed AC plasma under low pressure in Ar atmosphere. The plasma polymerized coating was characterized by ATR Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Different thicknesses of poly(4-vinyl pyridine) coating under different plasma polymerization conditions were studied. Silver nanoparticles with diameter around 50nm deposit were precipitated on the poly(4-vinyl pyridine) coating by UV irradiation in Silver nitride water solution, in order to enhance the anti-microbial properties. Different kinds of modified PET films were tested for anti-microbial properties against yeast (Debaryomyces hansenii) by using microbiological analyser µ-4200 and direct microscopic count method.     

Comparison of nano- and microfibrillated cellulose films

Nanocellulose is an interesting building block for functional materials and has gained considerable interest due to its mechanical robustness, large surface area and biodegradability. It can be formed into various structures such as solids, films and gels such as hydrogels and aerogels and combined with polymers or other materials to form composites. Mechanical, optical and barrier properties of nanofibrillated cellulose (NFC) and microfibrillated cellulose (MFC) films were studied in order to understand their potential for packaging and functional printing applications. Impact of raw material choice and nanocellulose production process on these properties was evaluated. MFC and NFC were produced following two different routes. NFC was produced using a chemical pretreatment followed by a high pressure homogenization, whereas MFC was produced using a mechanical treatment only. TEMPO-mediated oxidation followed by one step of high pressure (2,000 bar) homogenization seems to produce a similar type of NFC from both hardwood and softwood. NFC films showed superior mechanical and optical properties compared with MFC films; however, MFC films demonstrated better barrier properties against oxygen and water vapor. Both the MFC and NFC films were excellent barriers against mineral oil used in ordinary printing inks and dichlorobenzene, a common solvent used in functional printing inks. Barrier properties against vegetable oil were also found to be exceptionally good for both the NFC and MFC films.     

Preparation and Barrier Properties of Chitosan-Layered Silicate Nanocomposite Films

Summary: In this study, chitosan nanocomposite films were prepared using a solvent-casting method by incorporation of an organically modified montmorillonite (Cloisite 10A). The effect of filler concentration on the water vapor permeability, oxygen permeability, mechanical and thermal properties of the composite films was evaluated. The structure of nanocomposites and the state of intercalation of the clay were characterized by XRD. The water vapor permeability of pure chitosan films was measured as a function of relative humidity (RH). It was found that the permeability value increased with an increase in RH. The water vapor and gas permeability values of the composite films decreased significantly with increasing filler concentration. Permeation data was fitted to various phenomenological models predicting the permeability of polymer systems filled with nanoclays as a function of clay concentration and aspect ratio of nanoplatelets. According to the XRD results, an increase in basal spacing was obtained with respect to pure clay for chitosan/clay nanocomposites. This demonstrated the formation of intercalated structure of clay in the polymer matrix. Tensile strength and elongation at break of the composites increased significantly with the addition of clay, however the thermal and color properties of the films were not much affected by the intercalation of clay into polymer matrix.     

The gas barrier coating of 3-aminopropyltriethoxysilane on polypropylene film

Nonporous films were formed on polypropylene (PP) films using 3-aminopropyltriethoxysilane (APTEOS) as the only precursor. The PP film was modified by corona-plasma treatment to provide appropriate adhesion between coating layer and substrate. Gas permeation properties of coating films were evaluated, and the influences of water ratio and film storing time on the gas permeability were investigated. Structural and surface properties of coating layers were characterized by ²⁹Si-NMR, FT-IR, and contact angle analyzer. The APTEOS coating films exhibit much higher barrier properties than PP film. The permeability coefficient of APTEOS coating film with water ratio of 3 is 0.011Barrer for nitrogen, 0.044Barrer for oxygen, and 0.002Barrer for carbon dioxide, while each permeability coefficient of PP bare film is 0.233, 0.858, and 2.886Barrer, respectively. The gas permeability coefficient is increased slowly along with storage time. Although additionally formed siloxane network may lead to a higher inorganic network density, the enhancement of gas permeability during storing period is largely attributed to film-swelling effect by the water vapor from atmosphere.     

Fabrication of photo‐cross‐linked polyethyleneimine‐based barriers for CO2 capture

In this study, first, polyethyleneimine was acrylated and mixed with polyvinyl alcohol solution to prepare photo‐crosslinked polyethyleneimine (PEI)‐based nanofibers by utilizing ultraviolet and electrospinning technique at the same time. For CO₂ permeability testing, same formulations were prepared by using solvent casting technique and exposed to ultraviolet light to have polyethyleneimine‐based membrane films. The chemical structures of the nanofibers were characterized by Fourier transform infrared spectroscopy. The thermal properties of nanofibers were examined by thermal gravimetric analysis and differential scanning calorimeter. The morphology of nanofibers was investigated by scanning electron microscopy. CO₂ permeabilities of samples were also measured. Copyright © 2015 John Wiley & Sons, Ltd.     

Biodegradable poly(propylene carbonate)/layered double hydroxide composite films with enhanced gas barrier and mechanical properties

Relatively well crystallized and high aspect ratio Mg-Al layered double hydroxides(LDHs) were prepared by coprecipitation process in aqueous solution and further rehydrated to an organic modified LDH(OLDH) in the presence of surfactant. The intercalated structure and high aspect ratio of OLDH were verified by X-ray diffraction(XRD) and scanning electron microscopy(SEM). A series of poly(propylene carbonate)(PPC)/OLDH composite films with different contents of OLDH were prepared via a melt-blending method. Their cross section morphologies, gas barrier properties and tensile strength were investigated as a function of OLDH contents. SEM results show that OLDH platelets are well dispersed within the composites and oriented parallel to the composite sheet plane. The gas barrier properties and tensile strength are obviously enhanced upon the incorporation of OLDH. Particularly, PPC/2%OLDH film exhibits the best barrier properties among all the composite films. Compared with pure PPC, the oxygen permeability coefficient(OP) and water vapor permeability coefficient(WVP) is reduced by 54% and 17% respectively with 2% OLDH addition. Furthermore, the tensile strength of PPC/2%OLDH is 83% higher than that of pure PPC with only small lose of elongation at break. Therefore, PPC/OLDH composite films show great potential application in packaging materials due to its biodegradable properties, superior oxygen and moisture barrier characteristics.     

Preparation of polyamide-6/chitosan composite nanofibers by a single solvent system via electrospinning for biomedical applications

This work was focused on preparation and characterizations of chitosan blended polyamide-6 nanofibers by a new single solvent system via electrospinning process for human osteoblastic (HOB) cell culture applications. The morphological, structural and thermal properties of the polyamide-6/chitosan nanofibers were analyzed by using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, Raman spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry (TGA). SEM images revealed that the nanofibers were well-oriented and had good incorporation of chitosan. FT-IR results indicated that the amino groups of chitosan existed in the blended nanofibers. TGA analysis revealed that the onset degradation temperature was decreased with increasing chitosan content in the blended nanofibers. The morphological features of the cells attached on nanofibers were confirmed by SEM. The adhesion, viability and proliferation properties of osteoblast cells on the polyamide-6/chitosan blended nanofibers were analyzed by in vitro cell compatibility test.     

Super Oxygen and Improved Water Vapor Barrier of Polypropylene Film with Polyelectrolyte Multilayer Nanocoatings

Biaxially oriented polypropylene (BOPP) is widely used in packaging. Although its orientation increases mechanical strength and clarity, BOPP suffers from a high oxygen transmission rate (OTR). Multilayer thin films are deposited from water using layer‐by‐layer (LbL) assembly. Polyethylenimine (PEI) is combined with either poly(acrylic acid) (PAA) or vermiculite (VMT) clay to impart high oxygen barrier. A 30‐bilayer PEI/VMT nanocoating (226 nm thick) improves the OTR of 17.8 μm thick BOPP by more than 30X, rivaling most inorganic coatings. PEI/PAA multilayers achieve comparable barrier with only 12 bilayers due to greater thickness, but these films exhibit increased oxygen permeability at high humidity. The PEI/VMT coatings actually exhibit improved oxygen barrier at high humidity (and also improve moisture barrier by more than 40%). This high barrier BOPP meets the criteria for sensitive food and some electronics packaging applications. Additionally, this water‐based coating technology is cost effective and provides an opportunity to produce high barrier polypropylene film on an industrial scale.

     

Correlation study among oxygen permeability,molecular mobility,and amorphous structure change of poly(ethylene‐vinylalcohol copolymers) by moisture

Oxygen permeability and the free‐volume hole size (cavity size) of ethylene‐vinylalcohol copolymers (EVOH) indicate abnormal humidity dependence, that is, they have minimum values in the range of around 20–40% RH, not showing a monotonic increase with humidity. To clarify this abnormal phenomenon, we investigated its molecular mobility and amorphous structure change by means of solid‐state NMR and temperature‐modulated differential scanning calorimetry (TMDSC). The glass transition temperature (T_g) decreased with humidity. Specimens stored at 15–60% RH showed large enthalpy relaxation, and it was found that the amorphous structure became more compact and the molecular conformation became more stable by ageing within this range of humidity. Under these conditions, solid‐state NMR measurement showed a component with intermediate relaxation time in the amorphous region. The results obtained by TMDSC and solid‐state NMR showed a reduction in molecular mobility by densifying in the amorphous region under the condition of 15–60% RH. The fact that the oxygen permeability and the cavity size of EVOH indicate minimum values at low humidity are attributed to the reduction in molecular mobility by enthalpy relaxation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1181–1191, 2009