Barrier Film Research Articles

A Review of Various Attempts on Multi-Functional Encapsulation Technologies for the Reliability of OLEDs.

As the demand for flexible organic light-emitting diodes (OLEDs) grows beyond that for rigid OLEDs, various elements of OLEDs, such as thin-film transistors, electrodes, thin-film encapsulations (TFEs), and touch screen panels, have been developed to overcome OLEDs’ physical and chemical limitations through material and structural design. In particular, TFEs, which protect OLEDs from the external environment, including reactive gases, heat, sunlight, dust, and particles, have technical difficulties to be solved. This review covers various encapsulation technologies that have been developed with the advent of atomic layer deposition (ALD) technology for highly reliable OLEDs, in which solutions to existing technical difficulties in flexible encapsulations are proposed. However, as the conventional encapsulation technologies did not show technological differentiation because researchers have focused only on improving their barrier performance by increasing their thickness and the number of pairs, OLEDs are inevitably vulnerable to environmental degradation induced by ultraviolet (UV) light, heat, and barrier film corrosion. Therefore, research on multi-functional encapsulation technology customized for display applications has been conducted. Many research groups have created functional TFEs by applying nanolaminates, optical Bragg mirrors, and interfacial engineering between layers. As transparent, wearable, and stretchable OLEDs will be actively commercialized beyond flexible OLEDs in the future, customized encapsulation considering the characteristics of the display will be a key technology that guarantees the reliability of the display and accelerates the realization of advanced displays.

Preparation and properties of biodegradable films made of cationic potato-peel starch and loaded with curcumin

The purpose of this study was to develop biodegradable films made of cationic potato starch-derivatives and loaded with curcumin. Potato starch was recovered from potato peel waste (PW). Cationic starch (CS) was obtained by modifying potato starch, mixed with curcumin and used to prepare composite films. Curcumin at low concentration was compatible with CS and was uniformly distributed in the CS matrix of the composite films. Compared with the pure cationic starch film, the incorporation of 5% curcumin increased the elongation at break (18%) and hydrogen-bonding interactions and reduced the water-vapor permeability (WVP) (21%) of the CS films. In addition, the mechanical properties of CS films were slightly improved, whereas the thermal stability of the CS films was unchanged. The CS/curcumin films showed excellent ultraviolet (UV) barrier performance and the addition of 5% of curcumin improved the UV blocking effect by 53.33%, but reduced the transparency by 47.74%. The composite films also had good antioxidant activity and the highest scavenging activity of DPPH and ABTS was 86.77% and 98.09% in the composite film containing 5% curcumin, and curcumin was rapidly released. In conclusion, this study shows that CS/curcumin composite films are potential bioactive packaging material for foods and can alleviate the problem of agricultural waste disposal. • The active biodegradable CS/curcumin composite film was prepared by solution casting method. • The addition of curcumin improved the UV barrier and mechanical properties of CS films. • The addition of curcumin improved the water vapor barrier and surface hydrophobicity of CS films. • The CS/curcumin composite films showed strong antioxidant activity. • The composite film had potential application value in the field of food packaging.

Physical, barrier, and thermal properties characterization of edible films from composite mixtures of starch and starch derivatives

In the search for sustainable and ecological alternatives in food packaging, the use of starch as one of the most abundant biopolymer resources to formulate edible films has been studied. Nonetheless, compatibility with other starch derivatives, such as dextrin and/or chemically modified starch, has not been explored yet. The objective of this research was to characterize opacity, water vapor barrier capability, and thermal properties of composite edible films, by a mixture design approach, formulated with three types of commercial chemical modified starch mixed with native corn starch and dextrin. Lower opacity in edible films was related to more soluble material, where the main effect of dextrin was the rise of soluble material and lower water vapor permeability. A more permeable film can be obtained with Nifrastarch and lower permeability with Gelamil. The type of chemically modified starch used in edible films for edible packaging can be decided according to the characteristics of the food in question, i.e., moisture, color, permeability, or edible film solubility for active packaging.

Analysis of volatile organic compounds produced during incineration of non-degradable and biodegradable plastics

As plastic consumption has increased, environmental problems associated with the accumulation of plastic wastes have started to emerge. These include the non-degradability of plastic and its disintegration into sub-micron particles. Although some biodegradable plastic products have been developed to relieve the landfill and leakage burden, a significant portion of discarded plastics are inevitably still incinerated. The concern here is that incinerating plastics may result in the emission of toxic volatile organic compounds (VOCs). Moreover, lack of policy and the limited market share contributes to the indiscriminate discarding of biodegradable plastics, whereby it is mixed and subsequently incinerated with non-degradable plastics. The aim of this study was therefore to qualitatively and quantitatively analyze the VOCs emitted from both non-degradable and biodegradable plastics during combustion employing gas chromatography mass spectrometry. Here, non-degradable poly(vinyl chloride) and poly(ethylene terephthalate) emitted 10-115 and 6-22 ppmv of VOCs, respectively. These emission levels were more than 100 times higher than the VOC concentrations of 0.1-0.5 and 0.1-1.8 ppmv obtained for biodegradable polyhydroxyalkanoate and polylactic acid, respectively. Notably, due to the presence of a repeating butylene group in both non-degradable and biodegradable plastics, 1,3-butadiene accounted for the highest concentration among the VOCs identified, with concentrations of 6-116 ppmv and 0.5-558 ppmv obtained, respectively. During the evaluation of gas barrier films employed for food packaging purposes, non-degradable aluminum-coated multilayered films emitted 9-515 ppmv of VOCs, compared to the 2-41 ppmv VOCs emitted by biodegradable nanocellulose/nanochitin-coated films. Despite the significantly lower levels of VOCs emitted during the incineration of biodegradable plastics, this does not represent suitable waste treatment solution because VOCs are still emitted during incomplete combustion. This study aims to encourage further research into diverse combustion conditions for plastics and stimulate discussions on the fate of discarded plastics.

A Fully Transparent, Stretchable Multi‐Layered Water Barrier Thin Film for the Passivation of Underwater Device Applications

AbstractRecent developments in wearable and embeddable electronic devices in physiological condition, such as neuroprobe and electroceuticals, have brought forth the need for a reliable passivation layer against water permeation into the devices. On top of the excellent waterproof barrier performance, the passivation layers must also be equipped with stretchability and dermatoid softness for the reliable operation of the devices without failure in the wet environment. Here, this work demonstrates a stretchable, superhydrophobic coating with excellent water barrier performance. The stretchable water barrier coating is formed by depositing alternating layers of a highly stretchable, superhydrophobic copolymer and a crosslinked organosiloxane polymer via initiated chemical vapor deposition. During the deposition, the organosiloxane polymer penetrates into the free volume of superhydrophobic copolymer to form a highly mixed network at the interface. Accordingly, a five‐layered coating shows excellent water and molecular barrier performance with no sign of degradation even at 60% of tensile strain. Moreover, this barrier film formed by vapor deposition is uniformly deposited on the substrate surface regardless of the type and morphology of the substrate. The highly stretchable water barrier coating developed in this study will serve as a promising candidate material for the passivation of various stretchable device applications.

Achieving a Superhydrophobic, Moisture, Oil and Gas Barrier Film Using a Regenerated Cellulose–Calcium Carbonate Composite Derived from Paper Components or Waste

It has been a persistent challenge to develop eco-friendly packaging cellulose film providing the required multiple barrier properties whilst simultaneously contributing to a circular economy. Typically, a cellulosic film made from nanocellulose materials presents severe limitations, such as poor water/moisture resistance and lacking water vapour barrier properties, related primarily to the hydrophilic and hygroscopic nature of cellulose. In this work, alkyl ketene dimer (AKD) and starch, both eco-friendly, non-toxic, cost-effective materials, were used to achieve barrier properties of novel cellulose–calcium carbonate composite films regenerated from paper components, including paper waste, using ionic liquid as solvent. AKD and starch were applied first into the ionic cellulose solution dope mix, and secondly, AKD alone was coated from hot aqueous suspension onto the film surface using a substrate surface precooling technique. The interactions between the AKD and cellulose film were characterised by Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) showing the formation of a ketone ester structure between AKD and the hydroxyl groups of cellulose. The presence of calcium carbonate particles in the composite was seen to enhance the cellulose crystallinity. The initial high-water vapour and oxygen transmission rates of the untreated base films could be decreased significantly from 2.00 to 0.14 g m−2 d−1, and 3.85 × 102 to 0.45 × 102 cm3 m−2 d−1, respectively. In addition, by applying subsequent heat treatment to the AKD coating, the water contact angle was markedly increased to reach levels of superhydrophobicity (>150°, and roll-off angle < 5°). The resistance to water absorption, grease-permeation, and tensile strength properties were ultimately improved by 41.52%, 95.33%, and 127.33%, respectively, compared with those of an untreated pure cellulose film. The resulting regenerated cellulose–calcium carbonate composite-based film and coating formulation can be considered to provide a future bio-based circular economy barrier film, for example, for the packaging, construction and agriculture industries, to complement or replace oil-based plastics.

Enzymatically Pretreated High-Solid-Content Nanocellulose for a High-Throughput Coating Process

There is an ever-increasing interest toward utilizing nanocellulose as barrier coatings and films, and recent studies have underlined the efficiency of using innovative fibrillation processes such as twin-screw extrusion with an enzymatic pretreatment for producing nanocellulose suspensions with solid contents as high as 20 wt %, which can lead to faster coating speeds and reduced drying energy costs. The current work aims at understanding the factors that influence high-throughput processability of high-solid-content nanocellulose during roll-to-roll coating. The rheological properties of 12.5, 10, and 7.5 wt % suspensions were evaluated across a wide range of shear rates and geometries (rotational, pipe, and slot). The influence of dispersants [carboxymethyl cellulose (CMC) and sodium polyacrylate (NaPA)] on the rheology and coating quality was assessed. A Casson-power-cross model is proposed to explain the rheological behavior across a wide shear rate range and is used to predict useful parameters, viz., yield stress, transition shear rate, and power-law index at high shear rates. Finally, a 12.5 wt % nanocellulose suspension with CMC or NaPA dispersant was roll-to-roll-coated on paperboard using a slot-die applicator. CMC addition had a positive influence on the yield stress, thixotropy, and water release and, therefore, resulted in a better mineral oil and grease barrier of the coated samples compared to the rest.

Fabrication and characterization of pullulan-based composite films incorporated with bacterial cellulose and ferulic acid

Pullulan-based composite films incorporated with bacterial cellulose (BC) and ferulic acid (FA) were prepared by solution casting method. The rheological, morphological, barrier, optical, anti-fogging, and antioxidant properties of pullulan-based composite films doped with BC and FA were investigated. The rheological results showed that all film-forming solution was pseudoplastic fluid and its viscosity increased with the increase of BC content. An appropriate BC (2 %) and FA were uniformly dispersed in pullulan to form uniform and dense composite films. With the increase of BC content, the roughness and opacity of composite films increased while their UV–vis barrier performance was improved by incorporating BC and FA. Fourier transform infrared spectrometer analysis demonstrated that hydrogen bond interactions among pullulan, BC, and FA were found, and incorporating BC could increase the crystallinity of the composite films, thus enhancing their mechanical, barrier, hydrophobic, and thermal stability properties. Pullulan-based composite films incorporated with 2 % BC and FA (P-BC2-FA) showed better mechanical properties, water, oxygen, and carbon dioxide barrier performances, and its water contact angle value also increased compared with control, respectively. P-BC2-FA film showed superior anti-fogging and antioxidant activities. These results indicate that the P-BC2-FA film are expected to be a potential target of bioactive packaging.

Mono and multilayer active films containing green tea to extend food shelf life

An active packaging film made of one and two-layers structure based on low-density polyethylene (LDPE) was produced with the incorporation of green tea extract (GTE) at different amounts by blown film extrusion. Film structure, optical, mechanical, antioxidant and barrier properties were characterized. The films revealed homogeneous film surface, the presence of GTE increases the tensile properties, improves friction coefficient and reduces LDPE films transparency. Moreover, the antioxidant capacity and barrier properties (water and oxygen) were enhanced, even at low concentrations. This study demonstrates the benefits of GTE incorporation into LDPE matrix, mainly in coextruded films, and its potential to develop an active and sustainable food packaging film at industrial scale.

Effect of the Passive Oxide Films Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Their Electrochemical Machining. Part 2. Anodic Dissolution of Titanium Alloys in Nitrate and Chloride Solutions

An experimental study of the anodic dissolution of titanium and its alloys, including pulsed dissolution (up to 100 A/cm2) under control of hydrodynamic conditions and surface temperature in nitrate and chloride solutions, showed that the process is carried out through the electrochemical formation of anodic oxide films (AOF) which can be chemically dissolved. An AOF has a bilayered structure, i.e. two barrier films on the interface with a metal and a solution. Its model is PDM-III (Point Defect Model). At certain conditions, it is possible to achieve a steady state in which the film growth rate is compensated by the rate of its chemical dissolution (observed at pulsed conditions). In this case, over 100% current efficiency based on the ionization of titanium in the oxidation state is achieved. During the conducted experiments, when treated with the direct current, the rate of the electrochemical formation of an AOF exceeded the rate of its chemical dissolution, which led to a decrease in to current efficiency which did not exceed 75%. An increase of the dissolution rate takes place with an increase in the electrolyte flow rate. Upon reaching the thermokinetic instability (TKI) of the AOF (thermal explosion due to a feedback rate of the electrochemical reaction-surface tem-perature-rate of an electrochemical reaction), the interaction of electrolyte components with the surface free of the film takes place, and, as a result, an “anomalous” anodic dissolution is observed with the current efficiency greater than 100%. Regardless the nature of the electrolyte, TKI is achieved at a current density of 1 A/cm2. It is shown that in nitrate solutions with certain parameters of pulsed processing (duty factor 2, dc 50%), the dissolution rate, and, in the case of electrochemical machining, the feed rate of a cathode-tool, can be more than twice higher than the rate of machining with the direct current of the same density.

Toray goes lunar, wins awards for anti-thrombogenic innovation, and develops ion-conductive membrane, multilayer plastic tube, antiviral particles and super high barrier film

On July 20, Toray Carbon Magic Co., Ltd. announced that it will take part in the Hakuto-R commercial lunar exploration program operated by Tokyo-based ispace, inc. as a supporting company. Toray Carbon Magic has been utilizing the optimization design and weight reduction technologies that it cultivated in years of race car development to help develop a carbon fiber-reinforced airframe and parts for the program's lunar lander, rover, and other equipment.

Size effect of carnauba wax nanoparticles on water vapor and oxygen barrier properties of starch-based film

Barrier properties against water vapor and oxygen were critical for starch-based nanocomposite film. In this study, size regulation of carnauba wax nanoparticle was utilized to adjust multi-scale structure of starch-based film, which intended to improve barrier properties. CW70 with 73.8 nm nanoparticle showed less disrupted starch hydrogen bonding, more ordered double helices, higher starch crystallinity and larger size of micro-ordered region compared with other nanocomposites. These changes of multi-scale structure of CW70 led to the lowest relative water vapor permeability (WVP, 0.86) and oxygen permeability (OP, 0.49) among all nanocomposites. Notably, water vapor could form new hydrogen bonding with starch, and the ratio of amorphous region was significantly negative correlated with WVP. Cohesive energy density was the determining factor for OP, and significant negative correlation was found between the size of micro-ordered region and OP. New knowledge from this study will advance the understanding of starch-based nanocomposite film barrier properties.

Design of a Flexible Thin-Film Encapsulant with Sandwich Structures of Perhydropolysilazane Layers.

Perovskite solar cells (PSCs) have attracted considerable attention due to their excellent photovoltaic properties, but stability issues have prevented their widespread application. PSCs must be protected by encapsulation to extend their lifetime. Here, we show that perhydropolysilazane (PHPS)-based multilayered encapsulation improves the lifetime of PSCs. The PSCs were encapsulated by converting PHPS into silica under vacuum ultraviolet (UV) irradiation. The PHPS-based multilayer encapsulation method achieved a sandwich structure of PHPS/poly(ethylene terephthalate) (PET)/PHPS with a water vapor transmission rate (WVTR) of 0.92 × 10-3 gm-2 d-1 (at 37.8 °C and 100% relative humidity). We then performed a reservoir test of the encapsulated PSCs to confirm the moisture stability of the encapsulation based on PHPS/PET/PHPS barrier films. The cell lifetime remained stable even after 1000 h of ambient-temperature operation. Finally, we analyzed the mechanical flexibility of the PHPS/PET/PHPS multibarrier through bending tests. The multibarrier exhibited high mechanical stability with no large increase in WVTR after bending.

Corrosion Behavior of Different Types of Stainless Steel in PBS Solution

Anodic and spontaneous corrosion of different types of stainless steel (AISI 304L, AISI 316L and 2205 DSS) in phosphate-buffered saline solution (PBS, pH = 7.4) at 37 °C (i.e., in simulated physiological solution in the human body) were examined using open circuit potential measurements, linear and cyclic polarization, and electrochemical impedance spectroscopy methods. After the anodic and spontaneous corrosion, the surface of the tested samples was investigated by light and scanning electron microscopy (SEM) with EDS analysis. It has been established that the tendency of the examined steel materials towards local corrosion decreases in the order: AISI 304L < AISI 316L < 2205 DSS. Namely, the possibility of repassivation and the resistance to local corrosion increases in the same order. The corrosion resistance of steel samples at open circuit potential is a consequence of forming a natural oxide film with a bi-layer structure and consists of an inner barrier and an outer porous film. The inner barrier film has a small thickness and extremely high resistance, while the outer porous film is much thicker but also has significantly lower resistance. The inner barrier layer mainly prevents corrosion of examined steel samples in order: AISI 304L < AISI 316L < 2205 DSS. Light microscopy and SEM/EDS analysis after pitting and spontaneous corrosion showed damage on the AISI 304L and AISI 316L surface, while the surface of 2205 DSS was almost undamaged by corrosion.

Surface Decoration and Functionalization on Polymerization-Induced Aramid Nanofibers: Implications for Barrier Films and Light-to-Heat Conversion

Surface Decoration and Functionalization on Polymerization-Induced Aramid Nanofibers: Implications for Barrier Films and Light-to-Heat Conversion

Influence of Gelatin-Based Coatings Crosslinked with Phenolic Acids on PLA Film Barrier Properties

Single-use plastics are a major source of pollution and biodegradable polymers could be the best substitute, as they possess similar barrier and functional properties. Aiming at improving barrier properties and providing antioxidant bioactivity, PLA (PolyLactic Acid) films were coated with a crosslinked suspension of plasticized gelatin incorporating phenolic compounds. The coating process induced weak modifications of PLA properties due to plasticization by moisture and glycerol from the coating suspension. Indeed, a double glass transition was displayed. The water vapor barrier properties of the PLA-coated films were not significantly affected. Phenolic compounds induced a crosslinking of the gelatin network, slightly decreasing the moisture sensitivity and surface hydrophilicity. Therefore, the mechanical properties of PLA were maintained after coating and their barrier properties were highly improved, with up to a 600-fold reduction of the oxygen transfer rate. These results make possible new applications for oxidation-sensitive foods, and even for semi-moist foods.

Development of Novel Blown Shrink Films from Poly(Lactide)/Poly(Butylene-Adipate-co-Terephthalate) Blends for Sustainable Food Packaging Applications.

Heat-shrinkable films, largely made of polyolefins and widely employed in the packaging sector as collation or barrier films, due to their short service life, are held responsible for high environmental impact. One possible strategy for reduction in their carbon footprint can be the use of biodegradable polymers. Thus, this work aimed to develop novel, heat-shrinkable, fully biodegradable films for green packaging applications and to analyze their functional performance. Films were obtained from blends of amorphous polylactic acid (PLA) and poly(butylene-adipate-co-terephthalate) (PBAT) at different mass ratios and compatibilized with a chain extender. They were produced by means of a lab-scale film blowing extrusion apparatus and characterized in terms of physical–mechanical properties and shrinkability. The influence of the processing parameters during the extrusion blowing process on the films’ behavior was investigated, highlighting the effects of blend composition and stretching drawing conditions. Shrinkage tests demonstrated that the produced films have shrinkability values in the typical range of mono-oriented films (ca. 60–80% in machine direction and ca. 10–20% in transverse direction). Moreover, the shrinkage in machine direction increases both with the mass flow rate, the take-up ratio to blow-up ratio and the bubble cooling of the film blowing process, and with the PLA content into the blend. In particular, films at higher PLA content also exhibit higher transparency and stiffness.

Poly(vinyl alcohol)/Kaolin Barrier Films with Superior Dispersion Fabricated by Solid-State Shear Milling and Biaxial Stretching

Poly(vinyl alcohol)/Kaolin Barrier Films with Superior Dispersion Fabricated by Solid-State Shear Milling and Biaxial Stretching

Characterization and application of almond gum-silver nanocomposite as an environmentally benign corrosion inhibitor for mild steel in 1 M HCl

Almond gum (AG)-Silver (Ag) nanocomposite (AG-AgNC) was biosynthesized and evaluated as a novel, inexpensive and green corrosion inhibitor for mild steel (MS) in 1 M HCl. The fusion of silver nanoparticles (AgNPs) in the AG biopolymer was confirmed by characterizing AG-AgNC by FT-IR, UV–Vis, XRD, EDAX, DLS and TEM techniques. Lattice planes FCC shown by XRD and observance of nano-size AgNPs in DLS and TEM along with the appearance of elemental Ag at 3 KeV in EDAX study confirmed the incorporation of AgNPs in the AG matrix. AG-AgNC was evaluated as an efficient corrosion inhibitor (C·I) from the gravimetric, PDP, EIS analysis of MS in 1 M HCl. AG-AgNC exhibited maximum inhibition efficiency (I.E) of 96.5% at 60 °C at 150 ppm which is almost double the I. E offered by the pristine AG. TGA showed increased thermal stability by the infusion of AgNPs in AG. EIS revealed the formation of an inhibitive barrier film at the MS/solution interface. PDP established that AG-AgNC is exhibiting a mixed-type inhibition. FTIR and UV–Vis described the interaction occurring between AG-AgNC and MS. Adsorption of AG-AgNC on MS followed Langmuir isotherm. SEM image defined improved surface morphology of MS due to the formation of a thin AG-AgNC film on MS. Appearance of O and Ag at 3 KeV in EDAX and mapping of inhibited MS further substantiated the formation of a compact film of AG-AgNC on MS.

Nonequilibrium Roughness Evolution of Small Molecule Mixed Films Reflecting Equilibrium Phase Behavior

Understanding non-equilibrium phenomena, such as growth, and connecting them to equilibrium phase behavior is a major challenge, in particular for complex multicomponent materials. We use X-ray reflectivity to determine the surface roughness of binary mixtures of several prototypical organic compounds. By analyzing the roughness as a function of composition, we find a systematic behavior depending on the bulk phase behavior in terms of intermixing, co-crystallization or phase separation. Supported by kinetic Monte Carlo simulations, we provide evidence that the growth behavior can be rationalized by a lowered step edge barrier in the mixed films which is induced by reduced in-plane crystallinity.