Search

Many plant materials in nature have the ability to change their shape to respond to external stimuli, such as humidity or moisture, to ensure their survival or safe seed release. A well-known example for this phenomenon is the pinecone, which is able to open its scales at low humidity due to the specific bilayer structures of the scale. Inspired by this, we developed a novel humidity-driven actuator based on paper. This was realized by the lamination of untreated paper made from eucalyptus fibers to a paper–carboxymethyl cellulose (CMC) composite. As observed, the hygroexpansion of the composite can be easily controlled by the amount of CMC in the impregnated paper sheet, which, thus, controls the morphologic deformation of the paper bilayer. For a more detailed understanding of these novel paper soft robots, we also studied the dynamic water vapor adsorption, polymer distribution and hygroexpansion of the paper–polymer composites. Finally, we applied a geometrically nonlinear finite element model to predict the bending behavior of paper bilayers and compared the results to experimental data. From this, we conclude that due to the complexity of structure of the paper composite, a universal prediction of the hygromorphic behavior is not a trivial matter. [ABSTRACT FROM AUTHOR]

The present study explored chitosan, a biodegradable nontoxic biopolymer, at different dosages for surface treatment of recycled paper to improve various properties relevant to packaging. Chitosan, at all applied concentrations, improved important paper properties like surface, strength and barrier due to which the low strength paper can also be used as a packaging paper. The effects of surface treatment of chitosan solutions of different concentrations on paper were analyzed by measuring breaking length, burst index, tear index, double fold, stiffness, air permeance, water vapor transmission rate (WVTR), wax pick, tensile energy absorption (TEA), and stretch. After surface treatment by 1% solution of chitosan, the breaking length, double fold, TEA, and stretch in machine direction were increased by 53.8%, 243%, 93%, and 75%, respectively, whereas burst index was increased by 38.4% in comparison with the base paper. The WVTR was reduced from 706 to 496 g/m2/24 h, and air passage time was increased from 18 to 65 Gurley s after surface treatment by 1% chitosan solution on the base paper. The chitosan solution at all the concentrations showed antibacterial activity in plate assay therefore reducing the susceptibility of paper to microbial attack. [ABSTRACT FROM AUTHOR]

Oil-in-water emulsions of different mass ratios of beeswax:chitosan (1:1, 3:1, and 5:1) in water were prepared using a high shear homogenizer for paper coating. The emulsions were analysed for particle size, zeta potential, viscosity, and creaming stability. The results showed that emulsions containing a 3:1 mass ratio of beeswax:chitosan were most stable with a minimum particle size (435 ± 18 nm), maximum zeta potential (− 33 ± 1 mV), and creaming stability (> 95%) during storage. Furthermore, kraft paper was coated with the emulsions, and its mechanical, and barrier properties were evaluated. The tensile and tear indices in the machine direction, burst index, folding endurance in the cross direction, and oil resistance significantly improved by 40%, 86%, 36%, 230%, and 220%, respectively. Compared with the control, the kraft paper coated with the most stable emulsions (3:1, beeswax:chitosan) showed a significant reduction in porosity (11%), water absorption (84%), and water vapour permeability (38%). The results suggested that the developed biocoatings can serve as an eco-friendly alternative to synthetic coatings, and the coated kraft paper can potentially be used in fast/oily food packaging. [ABSTRACT FROM AUTHOR]

Improving the shelf lives of fruits is challenging. The biodegradable polysaccharide pullulan exhibits excellent film-forming ability, gas barrier performance, and natural decomposability, making it an optimal material for fruit preservation. To overcome problems of high cost and film porosity of existing packaging technologies, we aimed to develop pullulan-based packaging paper to enhance the shelf lives of fruits. A thin paper coating comprising a mixture of 15 wt.% pullulan solution at various standard viscosities (75.6, 77.8, and 108.5 mPa·s) with tea polyphenols (15:2) and/or vitamin C (150:1) improved the oxygen transmission rate (120–160 cm3 m−2·24 h·0.1 MPa), water vapor transmission rate (<5.44 g·mm−1 m−2·h·kPa), maximum free radical clearance rate (>87%), and antibacterial properties of base packaging paper. Grapes wrapped with these pullulan-based papers exhibited less weight loss (>4.41%) and improved hardness (>16.4%) after 10 days of storage compared to those of control grapes (wrapped in untreated/base paper). Grapes wrapped with pullulan-based paper had >12.6 wt.% total soluble solids, >1.5 mg/g soluble protein, >0.44 wt.% titratable acidity, and ≥4.5 mg 100 g−1 ascorbic acid. Thus, pullulan-based paper may prolong the shelf life of grapes with operational convenience, offering immense value for fruit preservation. [ABSTRACT FROM AUTHOR]

Infiltration of binary solution of hexane and ethanol into chromatography paper associated with their evaporation was found to generate unexpected initial rapid advancement of wicking front followed by its receding and readvancing in our previous research. In the present study, paper chromatography development of hydrophobic dye, Sudan III, and hydrophilic dye, Acid Blue 9, was carried out using binary solutions of hexane and ethanol in open environment, allowing the developing solvent been evaporated. Sudan III was developed with initial rapid advancing wicking front, while Acid Blue 9 was scarcely developed. On the other hand, Acid Blue 9 was developed with the readvancing second wicking front, while the spot of Sudan III scarcely migrated. Thus, the unexpected illusional phenomenon, overtaking the spot of Sudan III by the spot of Acid Blue 9, was observed. The readvancement of the second wicking front was found to be enhanced as increasing the relative humidity in the environment. Surface temperature of the chromatography paper was measured during the chromatographic development in open environment to show that it became lower than the dew point when the experiments were carried out in relatively high humidity. Solubility of Sudan III in a binary solution of ethanol and water remarkably decreased as increasing the content of water. It was thus suggested that the water vapor condensation to induce water mixing into the mobile phase to decrease the solubility of Sudan III to inhibit its chromatographic development to realize the illusional spot overtaking of dyes of their chromatographic development associated with solvent evaporation. [ABSTRACT FROM AUTHOR]

Targeted synthesis of a new representative of colored pyrrol-2-one derivatives bearing an acceptor butadienetricarbonitrile fragment in the structure was carried out. The possibility of reversible water addition to the dye was shown, which was accompanied by an unaided eye-recognizable color change from orange to almost colorless. The reversibility of water addition was supported by the possibility to shift the reaction equilibrium using the temperature changes. The sensitivity of the dye to water was preserved on the filter paper, making it possible to describe the potential of using the system to alter the color of a material under the action of a combination of stimuli, such as water vapor and temperature. [Display omitted] • The first water-sensitive dye of butadienetricarbonitrile series was synthesized. • The reversible reaction of the dye with water is recognized by an unaided eye. • Paper with the applied dye undergoes coloring/bleaching cycles due to the action of water vapor and temperature. • The possibility of writing characters on paper and two methods of erasing them were demonstrated. [ABSTRACT FROM AUTHOR]

This work evaluates the effect of spray-coating papers using cellulose nanofibrils (CNFs) and nanoclay (NC) on the mechanical and barrier properties for application such as reinforced packaging bags. Sack kraft papers of 60 g m−2 (C60) were coated with combinations of CNFs and CNFs + NC, varying the number of layers on the internal face (IF) and external face (EF) of the paper. Their properties were compared to uncoated sack kraft papers with basis weight of 60 g m−2 (C60), 80 g m−2 (C80) and 120 g m−2 (C120). The amount of CNF/NC deposited was ~ 20 g m−2 while the CNF layer deposited was ~ 10 g m−2 on the sack papers. Increase in the number of layers deposited decreased the water vapor transmission rate (WVTR) compared to C60. CNF layer had lower contact angles on the coated papers than CNF/NC layer. The coated papers also showed a 44–66% increase in tensile index when compared to C120. Papers coated with 2 layers of CNFs and 1 layer of CNFs /NC achieved the same tensile index as C120 and the layers also resulted in higher values of Young's modulus (38–56%) when compared to C60. Spray-coating, with the appropriate layers, improved the mechanical and barrier properties of the coated papers, and is a possible alternative to producing papers with lower basis weight and using renewable raw materials. Additionally, the mixture of two hydrophilic components, such as nanofibrils and NC can result in a coating with more hydrophobic characteristics. [ABSTRACT FROM AUTHOR]

A high-barrier, strong, and antibacterial paper was fabricated by coating the acetylated cellulose solution with different contents of cinnamaldehyde (CIN) on Kraft paper. The antibacterial, antioxidant, mechanical, and barrier properties of coated paper were investigated. When the amount of CIN added in coating reached 6% v/v, the coated paper exhibited excellent antioxidant activity and antibacterial activity against Escherichia coli and Staphylococcus aureus. Notably, the dry and wet tensile strength of paper after coating was increased by 26.4 and 10.6 MPa, respectively. Furthermore, the coated papers' barrier properties against oil, water, water vapor, and oxygen were dramatically improved, especially for the water barrier rate up to 96.4%. Our coated papers with over 6% v/v CIN could extend beef's shelf-life for at least 4 days, which exhibited a promising prospect in eco-friendly antibacterial packaging. [ABSTRACT FROM AUTHOR]

Herein we report the development of bilayer‐coated‐paper with corn starch as the bottom layer and zein protein as the top layer. Two different methods were used for preparation of the coated paper, namely rod‐coating and dip‐coating techniques. The effect of the coating methods was studied by investigating the mechanical and barrier properties of the coated paper. A significant decrease of the water vapor and oxygen transmission rates at various temperatures and relative humidity conditions was observed. Considering the growing need for renewable and biodegradable alternatives to conventional plastics, the coated paper described herein may have strong potential for applications in the food packaging sector. [ABSTRACT FROM AUTHOR]

As reported herein, a bilayer coating approach using poly(vinyl alcohol) (PVOH) and zein is employed to enhance the water vapor and oxygen barrier properties of paper materials. The coating was applied onto three different types of paper substrates to study the general applicability of this approach. The bilayer‐coated paper samples exhibited a reduction of up to 65% in their water vapor transmission rate in comparison to the corresponding uncoated paper substrates at 23°C and 50% relative humidity. In addition, the bilayer‐coated paper samples showed at least a 40‐fold decrease in oxygen transmission rate from that of the uncoated paper samples. In addition, the coated paper showed excellent thermal stability and mechanical properties. Scanning electron microscopy confirmed that the obtained coated paper has a smooth texture without pores. Pulp was recovered from the coated paper by washing with water/ethanol. Thus, this work provides a unique coated paper with excellent barrier properties and therefore has the potential for real‐world application as an alternative to single‐use plastics. [ABSTRACT FROM AUTHOR]

In the context of green development, different types of waste paper were used in this study to prepare environment-friendly nanocellulose membrane by using different pretreatment processes. The results showed that all nanocellulose membranes had a novel microscopic composite morphology: nanocellulose fibers in the middle were tightly arranged and had a certain direction, while nanocellulose fibers at the edge were arranged randomly. Moreover, the type of waste paper affected the formation and property of nanocellulose membranes deeply compared with the pretreatment process. Nanocellulose membrane prepared from office waste paper had a high transmittance (50.8 %) and low oxygen transmission rate (1.548·10−3/cm3mm/(m2·d·KPa)) while that prepared from waste corrugated paper had a high yield (50.63 %), high folding number (81 times), and low water vapor transmission rate (1550.24 g·m−2·day−1). Meanwhile, nanocellulose membrane prepared without any deinking treatment had a significant performance advantage in terms of water vapor barrier and folding resistance. Therefore, in actual application, deinking treatment can be selectivity omitted, which will simplify the preparation process flow and reduce the production cost of nanocellulose membrane. Furthermore, in order to satisfy different application requirements, the appropriate raw materials and treatment processes can be chosen to prepare nanocellulose membranes with different properties. This study provides a simple and low-cost way to prepare high-performance environment-friendly self-assembled nano membrane material, and also achieves the high value utilization of waste paper, which has a certain ecological, economic, and social benefits. [Display omitted] • Prepared CNC membrane with a self-assembled microscopic composite nanostructure. • Produced functional transparent CNC membrane with low cost and high performance. • Facilitated the simply of preparation process of green CNC membrane. • Proposed a novel way to achieve the high value utilization of waste paper. [ABSTRACT FROM AUTHOR]

BACKGROUND: Different thermoplastic starch (TPS) films were prepared with or without the addition of microcrystalline cellulose (MCC) obtained via the melt‐extrusion method, and then the hot‐press method was used to produce environmentally friendly TPS‐based film/paper composites to replace petroleum‐based materials. RESULTS: The paper–plastic composites exhibited good interfacial adhesion from the scannign elctron microscopy images. It was seen that 5 wt.% MCC was added to reinforce the mechanical properties of TPS films, such that it also improved the barrier properties of MCC@TPS/paper composites and extended the path of water vapor through TPS films, which decreased the water vapor transmission rate of MCC@TPS/paper composites. TPS/paper composites and MCC@TPS/paper composites have better physical properties (i.e. smoothness, flexibility and folding resistance) than only paper. In particular, it was found that the water contact angle of MCC@TPS/paper composites and TPS/paper composites were higher than single‐layer paper. Furthermore, MCC reinforced paper–plastic composites demonstrated good barrier properties which can meet the requirement of the need for lower water sensitive materials in the food packaging industry. CONCLUSION: Thermoplastic corn starch‐based film/paper composites have good application properties as a potential source of bioplastic materials. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Developing environmentally friendly barrier coatings as an alternative to petroleum-based polymer packaging is a challenge. Cellulose nanofibres (CNF) films have exhibited great potential as water and gas barrier layers. Recycled paper was multi-layer coated with three commercial CNF (mechanical (M-CNF), TEMPO (T-CNF) and carboxymethylated (C-CNF)) using two metering systems (wound rod and blade micrometer) and two drying methods (tension-free contact drying and air drying). The coatability and rheological behaviour of the CNF suspensions were analysed. The gas, water and grease barrier properties of the CNF coated papers were determined and compared with the results of paper coated with cationic starch. The three CNF suspensions and the starch suspension were successfully coated using both metering systems. In the multi-layer coating, air drying yielded higher coat weights than contact drying, and the difference was more noticeable in M-CNF and T-CNF coated samples. A lack of uniformity observed in CNF coatings increased with the number of coating layers. M-CNF coated samples had a whitish surface with a uniform appearance, but coating was insufficiently compact to provide barrier properties. T-CNF coating exhibited a cracked surface and consequently provided no barrier properties. Drying stresses caused breakage of T-CNF coating, which could be explained by the drop in apparent viscosity at much lower rheological shear stresses in the T-CNF suspension. C-CNF showed successful coatability and provided barrier properties to paper with both metering systems and drying methods. Air permeance decreased considerably and the water wettability of the paper decreased by 60% compared to the reference paper, even with a single coating layer (about 1 g·m−2). In addition, a greaseproof paper (grease resistance >1800 s and kit no >10) was obtained with multi-layer C-CNF coating. Although water vapour permeability at 90 % RH and 20 °C decreased slightly with a single layer of CNF coating, higher amounts of CNF did not improve this parameter. • Evaluation of CNF coatability in metering and drying systems employed in papermaking • Air stream drying led higher CNF coat weights in multi-layer application. • Cracked coating under drying stresses was related to rheological behaviour of CNF. • Carboxymethylated CNF can be used as pre-coating to improve paper barrier properties in papermaking. • A greaseproof paper by multi-layer carboxylated CNFs coating could achieved [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A sustainable development requires the use of bio-based packaging materials because of ready availability and limited environment impact. The porous structure and hydrophilic nature of cellulose in paper based materials needs to be combined or laminated with other materials to overcome these limitations. The fiber found in the banana stems and leaves, it is possible to use these raw materials in pulp processing and banana flour can be produced into an edible film. The aim of the study was to discover a suitable method (wet lamination or dry lamination) for producing paper (stems, leaves, or a 1:1 ratio of mixed stems and leaves) lamination with banana film and to study their physical properties for packaging application. Banana flour (4%) solution was used as adhesive media between paper and film for wet lamination process where as the heating and compression were applied for dry lamination process. The results showed the efficiency of banana stems for paper production. However, there was an improvement in results when a 1:1 ratio of mixed stems and leaves was used due to an increase in tensile strength, elongation, and the L value. There was no significance in the water vapor permeability in all treatments. All treatments of paper lamination expressed 6 - 13% moisture content. The separation of film and paper layers occurred in dry lamination samples. The wet lamination of the leaf paper and mixed paper caused high tensile strength and elongation. Therefore, it could be used as an alternative and environmentally friendly method in the application of packaging materials. [ABSTRACT FROM AUTHOR]

Summary: The cost‐effective strategy of using paper‐based materials as alternatives to plastics can aid in reducing environmental stress. Herein, a novel green low‐carbon paper‐based food‐packaging composite was synthesised: curcumin microcapsule‐polyvinyl alcohol/beeswax/chitosan (CURM‐PVA/BW/CS) composite papers. Scanning electron microscopy and X‐ray diffraction results confirmed that curcumin was successfully encased and adhered to the paper. The water vapour permeability and oxygen transmission rate of the composite papers were 42.28 g (m2·d)−1 and 3.41 cm3 (m2·d·atm)−1, respectively. The antioxidant capacity of paper was 93.53%, and the mechanical properties were effectively improved by adding natural antioxidants to the coating. Finally, cakes were packaged in the biodegradable 1%CURM‐PVA/BW/CS papers exhibited optimal preservation during the storage period, based on the characterisation of the cake peroxide value, acid value and microbiological count. Overall, the CURM‐PVA/BW/CS paper showed great potential for food packaging. [ABSTRACT FROM AUTHOR]

Wrapping paper has an irreplaceable role in the food industry, but the high hydrophilicity of cellulose-based wrapping paper limits its application. Here, we aim to develop a fluorine-free and stable method for preparing the superhydrophobic cellulose-based paper using KH570-modified-n-TiO2 and ε-polylysine (ε-PL) to construct a superhydrophobic surface by layer-by-layer self-assembly. The paper modified by (ε-PL/KH570-modified-n-TiO2)4 multilayers has superhydrophobic and self-cleaning properties after heat treatment. The water contact angle reaches up to 152.8° and the antibacterial rate is close to 100%. The high barrier properties to water vapor better prolong the shelf life of cherries. Therefore, the (ε-PL/KH570-modified-n-TiO2)4 multilayers modified paper can provide a new idea for food preservation. The advantage of the double-layer assembly is that even if the superhydrophobic layer of the wrapper is worn away and lost, the remaining ε-PL is still able to act as a bacterial inhibitor, ensuring that the food is not perishable. [ABSTRACT FROM AUTHOR]

In this study, hemp-based barrier papers were produced by a facile film coating route. The hemp plant was mechanically separated by crushing and breaking down the stalks. The woody hurd and fibers were separated manually. Then, cellulosic pulp was prepared by the Kraft method. Alkali treated hemp fibers were used for the paper preparation, and papers were coated with poly(lactic acid) (PLA) films. Physical, morphological, structural, wetting, mechanical properties, thermal dimensional stability, and water vapor permeability (WVP) properties were analyzed. Average hemp fiber diameter decreased by around 50% after alkali treatment. It was also found that dry and wet tensile strength values for PLA-coated hemp papers increased 3- and 2-orders of magnitudes, respectively. Also, PLA-coated hemp papers showed 0% shrinkage in the temperature range from 100°C to 200°C. WVP of PLA-coated hemp papers decreased by around 50% compared to hemp paper at the end of 300 h. [ABSTRACT FROM AUTHOR]

Summary: It is well recognized that combining nonpotable water with solar energy to desalinate water and produce water vapor is an effective route to solve the shortage of fresh water. However, the solar vapor generation suffers from either low solar energy efficiency or complex and high‐cost devices. Herein, we explore a black membrane based on polypyrrole (PPy) and filter paper to enhance solar‐to‐vapor conversion performance, thus providing a low‐cost, stable, and strong efficient solar vapor generator. This device displays high solar‐to‐vapor conversion efficiencies of up to approximately 92.2% and 95.6% under irradiation of 1 and 4 kW m−2, respectively. Therefore, this paper‐based high solar‐to‐vapor conversion and scalable evaporator provides a promising solution to the problem of freshwater scarcity and nonrenewable recourses. [ABSTRACT FROM AUTHOR]

Herein, we report on conductive ultrathin films (nanosheets) with the characteristics of stretchability and water vapor permeability for skin-conformable bioelectrodes. The films are fabricated by combining conductive fibrous networks of single-wall carbon nanotubes (SWCNTs) and poly(styrene-b-butadiene-b-styrene) (SBS) nanosheets (i.e., SWCNT-SBS nanosheets). An increase in the number of SWCNT coatings increases both the thicknesses and densities of the SWCNT bundles. The SBS nanosheets coated with three layers of SWCNTs (i.e., SWCNT 3rd-SBS nanosheets) show comparable sheet resistance to the SBS nanosheets coated with poly(3,4-ethylenedioxithiophene) doped with poly(4-styrenesulfonate acid) (PEDOT:PSS) containing 5 wt.% butylene glycol (i.e., PEDOT:PSS/BG5-SBS nanosheets). In addition, the SWCNT 3rd-SBS nanosheets exhibit significantly reduced elastic moduli and increased elongations at break compared to the PEDOT:PSS/BG5-SBS nanosheets. Furthermore, the calculated water vapor transmission ratio of the 210-nm-thick SBS nanosheets (268,172 g m−2 (2 h)−1) is greater than that of the filter paper (6345 g m−2 (2 h)−1). The SWCNT 3rd-SBS nanosheets attached to model skin show high tolerances to bending and artificial sweat at different pH values (i.e., the electrical resistance changes ~1.1 times). Finally, the SWCNT 3rd-SBS nanosheet is applied to detect the surface electromyogram from the forearm of a subject. This nanosheet displays a signal-to-noise ratio similar to that of the PEDOT:PSS/BG5-SBS nanosheet. We report on conductive ultrathin films (referred to as "nanosheets") with stretchability and water vapor permeability for skin-conformable bioelectrodes. By combining conductive fibrous networks of single-wall carbon nanotubes and poly(styrene-b-butadiene-b-styrene) continuous nanosheets (i.e., SWCNT-SBS nanosheets), the conductive nanosheet shows a high tolerance to bending on a model skin sheet and a high permeability to humidity. Finally, we demonstrate that the conductive nanosheet can detect the surface electromyogram signals from a subject's forearm. [ABSTRACT FROM AUTHOR]

The present study concerns a practical approach to survey water sorption properties of ionic liquid ([EMIM]OAc) treated papers with and without chemical crosslinking. Ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) can be used to transform sulfate pulp paper to regenerated cellulose film-like material. The fusion process increases both the dry and wet strength of the paper, improves oxygen and grease barrier properties, and increases paper transparency. The transformation is brought about by dissolution of the surfaces of the cellulosic fibers followed by precipitation and fusion of the fiber surfaces. Treatment conditions can be adjusted to produce partial dissolution of the fibers resulting in paper-like materials with improved wet-strength, or to achieve substantial or full dissolution resulting in transparent, regenerated cellulose film-like materials. From the industrial feasibility point of view, understanding the water sorption properties of IL-treated paper and the process parameters to control it are crucial. Results show that the treatment makes the paper more sensitive to both liquid water and water vapor, the magnitude depending on the degree of fiber dissolution and restraint of sheet shrinking during the treatment. Decreased water absorption and improved sheet dimensional stability were achieved by use of chemical crosslinking. [ABSTRACT FROM AUTHOR]

Single use packaging is one of the major contributors to environmental issues linked to waste in the environment. Packaging materials often consist of several plastics, which, when combined, are difficult to recycle. One option to reduce these issues are packaging materials for which recycling infrastructure and end markets exist, such as paper. Use of paper in food packaging applications is limited due to poor barrier properties. Enhancing barrier properties without impacting recyclability can be achieved by thin polymeric coatings combined with vapour‐deposited aluminium. Water vapour transmission rate (WVTR) of packaging materials is often assessed at 38°C and 90% relative humidity (RH). These conditions, not experienced in the supply chain, may not be optimal for paper as they have the potential to alter the structure of paper by inducing expansion disrupting barrier. This study aims at verifying this hypothesis by evaluating the influence of temperature and RH on the measured WVTR of high barrier paper. Results show that testing such papers at 38°C and 90% RH yields WVTR approximately 10 times higher than when tested at 23°C and 85% RH. The link between this increase and the disruption of the barrier layer is demonstrated by testing samples preconditioned at 38°C and 90% RH and tested at 23°C and 85% RH, depicting an increased WVTR as well. Results suggest that integrity of barrier layer in paper was disrupted at 38°C and 90% RH, and hence, these conditions are deemed inappropriate for testing barrier performance of paper materials. [ABSTRACT FROM AUTHOR]

Biodegradable chitosan can be applied as a coating on the surface of kraft paper in order to improve its barrier properties against water vapor and air. The food packaging industry can benefit from the addition of chitosan to its current packaging, and in turn reduce pollution from plastic packaging plants. This paper discusses the film formation of chitosan, the permeability of paper coated with a chitosan layer, and the influence on the paper's surface and barrier properties under different process conditions. SEM (scanning electron microscope), AFM (atomic force microscope), ATR-FTIR (Fourier transmission infrared spectroscope with attenuated total reflection), and PDA (penetration dynamics analysis) were used to analyze the properties of chitosan's film formation and permeability. A controlled experiment showed that the chitosan layer was smoother than the surface of the uncoated kraft paper, had better film formation, and that there was no chitosan penetration through the kraft paper. The barrier properties against water vapor were strongest when there was a higher concentration of chitosan solution at the optimum pH, stirring speed, and those with a thicker coating on the kraft paper. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess selected properties of coatings incorporating nanocellulose, with the potential of being applied as a surface modification for cellulosic and lignocellulosic materials, particularly for applications within biodegradable packaging. Cellulose nanocrystal (CNC) and cellulose nanofibril (CNF) coatings were produced and applied on both sides of pure cellulose samples in the form of filter paper with a Mayer bar. Selected organosilicon compounds, albumin, and the TEMPO reagent were used as additional modifying substances. Coating parameters were determined, such as water contact angle, water absorption, hygroscopicity, and tensile strength. The presence of the coatings resulted in a significant increase in water vapor absorption by the substrate. Nanocellulose coatings proved to be sensitive to the water vapor and showed no barrier properties against it. However, the samples coated with nanocellulose had a noticeably lower tendency to absorb liquid water. The samples coated with modifying substances had a contact angle of ≥90°, proving that such coatings were an additional barrier to the penetration of liquid water. In the case of cellulose material coated with nanocellulose (i.e., without the addition of silane), there was no barrier effect established, thereby allowing full wetting of the substrate. The nanocellulose coatings increased the tensile strength of the samples. This increase was observed for all tested coating variants. The results obtained offer several potential routes to the manufacture of more environmentally friendly coatings and packaging materials. [ABSTRACT FROM AUTHOR]

The use of clay filler materials in dispersion coatings is a well-established method to provide improved barrier properties to the coated paper substrate, in particular lowering the water vapour transmission rate (WVTR) through the coating. In this paper we demonstrate the use of small spherical silica particles (È100-220 nm) as an additive to a clay-latex coating formulation is able to provide further improvements to the barrier properties, when compared to the equivalent silica-free coatings. A significant decrease in both the water vapour transmission rate and the direct water uptake of water (Cobb120 wettability test) is observed for coatings containing as little as 1% silica additive.

Developing a feasible and low-cost approach to fabricate recyclable, UV-shielding, biodegradable as well as water- and oil-resistant coating for paper substance is still a challenge. Herein, novel full-biobased chitosan-derived cardanol glycidyl ether (CS- x CGE, x = 1/8, 1/4, 1/2, and 1) coatings with different contents of cardanol glycidyl ether (CGE) were developed for paper substance via the ethoxylation of cardanol and sequent addition with chitosan in a one-pot process. Benefiting from the hydrophobicity and ultraviolet resistance of CGE, the resultant CS-CGE (x = 1) coated paper exhibited not only remarkable oil resistance (kit rating value of 11/12), but also water resistance (Cobb 60 value of 5.78 g/m2), UV shielding and excellent recyclability. Compared with the uncoated paper, the mechanical properties of CS-CGE coated paper including tensile strength, folding strength, and resistance of water vapor permeability were improved 25 %, 63 %, and 73.4 %, respectively, which could be ascribed to the flexible long-alkyl chain in the structure of CS-CGE and the continuous and homogeneous CS-CGE derived film covered in paper substance. Most importantly, CS-CGE film is biodegradable when it is only buried in soil. This study affords a feasible and sustainable strategy for large-scale fabrication of full-biobased, recyclable, UV-shielding, water and oil resistant, as well as biodegradable coating for green paper-derived packaging. [Display omitted] • Full-biobased chitosan-derived coating is fabricated via the one-pot reaction. • The coating imparts paper substance excellent water, oil, air, and UV resistances. • The coating exhibits not only excellent recyclability but also biodegradability. [ABSTRACT FROM AUTHOR]

A green and facile method was proposed to prepare robust and fully bio-based modified paper in this study, which involved in layer-by-layer deposition of chitosan (CS) and mussel adhesive protein-mimetic polymer (dopamine-grafted carboxymethyl cellulose, CMC- g -DA) on paper surface and subsequent oxidative cross-linking by sodium periodate. The mechanical, barrier and antibacterial properties of the cross-linked multilayer-modified paper significantly improved with the increased bilayer numbers. Compared with unmodified paper, cross-linked (CS/CMC- g -DA) 6 multilayer-modified paper exhibited 71.6 % improvement in tensile strength, 69.2 % and 56.3 % decline in air and water vapor permeability, as well as above 90 % antibacterial efficiency against S. aureus and E. coli. Particularly, the cross-linked multilayer-modified paper maintained outstanding functional stability even after suffering from vigorously corrosive treatment. The obtained functional paper effectively extended the shelf-life of Agaricus bisporus to 6 days under ambient conditions. We believed that the prepared robust functional paper in this study will have promising application prospect in food packaging field. [ABSTRACT FROM AUTHOR]

Abstract: Paper is still regarded as the most common carrier of information. Encouraged by environmental policies, the papermaking technology recently changed, resulting in an increased production of recycled paper. Two types of contemporary paper, non-recycled and recycled, were thus investigated to evaluate possible differences in their rate of degradation. The analyses were carried out using unaged paper to evaluate acidity, dry matter and ash content, lignin presence, and fibre furnish. Accelerated ageing experiments were performed at different temperatures (50-80 °C) and water vapour pressures (90.5-227.5 torr). Viscometric measurements were carried out to evaluate the extent of paper degradation as a function of time, upon various accelerated ageing conditions. The results indicate that the rates of degradation follow first-order kinetics with respect to scission of glycosidic bonds, the rate constants for recycled paper being found to be slightly higher than the corresponding constants for non-recycled paper, but comparable within experimental limits. The kinetic constants did not display a monotonic trend with increasing water vapour pressures. The Arrhenius dependence of the rate constants on temperature for both kinds of paper supplied the activation energies, which fall in the typical range expected for paper degradation. Finally, the measured rate constants fit fairly well the recently modelled dose-response function for historic paper. Colour changes were found to be visible to the human eye for samples aged for more than 40 days at 60, 70 and 80 °C.Graphical abstract: [ABSTRACT FROM AUTHOR]

Pigments are often added to improve the barrier performance of dispersion coatings on paper, but they only are beneficial up to a limited pigment volume concentration (PVC). In this study, the use of montmorillonite (MMT) as pigment was explored in latex emulsions synthesized using surfactant and Pickering emulsion methods to explore the origins of this limitation. MMT was used to synthesize dispersion coatings for paper consisting of poly(styrene- co -butylacrylate) latex and compared with those synthesized using sodium dodecyl sulfate (SDS) surfactant. The Pickering, surfactant, and commercial coating systems with MMT decreased the water vapor transmission rate (WVTR), reaching minimum values at 1.2 %, 2 %, and 0.4 % PVC, respectively. At higher PVC values, the WVTR of all systems increased, which was attributed to the MMT pigments creating pathways for water transport. Moreover, similar pore volumes were found in all the latex films, indicating that the decrease in barrier properties as PVC increased was not caused by pore generation. The hydrophilicity of the MMT pigment was found to contribute to the observed minimum and lower barrier properties with increasing PVC. This work demonstrates that addition of pigments to the latex can be beneficial to improve paper barrier properties up to a certain level beyond which the pigments form percolation networks along the interfaces between MMT and the polymer, reducing the barrier properties. • Montmorillonite was used as a Pickering emulsion stabilizer to synthesize latexes • Latexes containing montmorillonite coated on paper reduced water vapor transmission • Above an optimum pigment volume concentration, water vapor transmission increased • Coating analysis indicated pore formation in the coating did not cause behavior [ABSTRACT FROM AUTHOR]

Food packaging manufacturers often resort to lamination, typically with materials which are neither non-biodegradable nor biobased polymers, to confer barrier properties to paper and cardboard. The present work considers a greener solution: enhancing paper's resistance to moisture, grease, and air by aqueous coating suspensions. For hydrophobization, a combined approach between nanocellulose and common esterifying agents was considered, but the water vapor transmission rate (WVTR) remained excessively high for the goal of wrapping moisture-sensitive products (>600 g m−2 d−1). Nonetheless, oil-repellant surfaces were effectively obtained with nanocellulose, illite, sodium alginate, and/or poly(vinyl alcohol) (PVA), reaching Kit ratings up to 11. Regarding air resistance, mineral-rich coatings attained values above 1000 Gurley s. In light of these results, nanocellulose, minerals, PVA, pullulan, alginate, and a non-ionic surfactant were combined for multi-purpose coating formulations. It is hypothesized that these materials decrease porosity while complementing each other's flaws, e.g., PVA succeeds at decreasing porosity but has low dimensional stability. As an example, a suspension mostly constituted by nanocellulose, sizing agents, minerals and PVA yielded a WVTR of roughly 100 g m−2 d−1, a Kit rating of 12, and an air resistance above 300 s/100 mL. This indicates that multi-purpose coatings can be satisfactorily incorporated into paper structures for food packaging applications, although not as the food contact layer. [ABSTRACT FROM AUTHOR]

Waterproof coating is necessary for paper-based packaging materials, especially as a plastic substitute in single-use applications. Currently, most paper-based packaging employs hazardous fluorocarbon coatings or other petroleum-based additives, which has caused a lot of concerns over safety. Herein, a novel edible waterproof coating was fabricated by a beeswax-in-water Pickering emulsion using hemicellulose-grafted-lauric acid (H-LA) micelles as nano-stabilizers. The fully biomass-based waterproof coating agent presented a uniform and stable water dispersion with a droplet size of around 1 μm. And compared with conventional surfactants, H-LA micelles stabilized at the oil–water interfaces and formed Pickering emulsions with enhanced stability. The Pickering emulsion was then applied as a coating of paper. The coated paper exhibited excellent water-resistance with a water contact angle of 130 ± 2.89° and an effective waterproof time of up to 6 h. The coated paper also showed good moisture barrier properties; the water vapor transmission rate was lower than 5.05 g mm m−2 day−1. Moreover, the waterproof coating was non-toxic, environmentally friendly and biocompatible, and could completely biodegrade in soil within 2 months. This work may provide an alternative solution for safe, cost-effective and sustainable paper-based packaging materials to replace traditional disposable plastics. [ABSTRACT FROM AUTHOR]

In the research, kraft paper was coated with a blend of chitosan and rice starch ultrasonic-treated coating solution. The novelty in this paper is the use of bio-based coating solution which was treated with ultrasound, which led to a positive effect on the mechanical, optical and water barrier properties. The goal of the research was to improve the coating solution with ultrasound and to make the coated kraft paper with chitosan and rice starch suitable for a packaging material. To evaluate the influence of the ultrasonic treatment on coating solutions, the moisture content, water vapour permeability, absorptiveness, tensile strength, elongation at break, tear and bursting strength, colour values, gloss and surface properties of coated paper were determined. The research showed that the moisture content in all coated papers decreased by less than 0.5%, the water vapour permeability reduction being around 20%. Tensile strength, elongation at break and tear strength improved at coated paper, even more at the one pretreated with ultrasound. Bursting strength, which is important at paper bags, increased by 9% at coated, and by 12% at coated and ultrasound-treated paper. Furthermore, gloss improved at both coated papers. As expected, the coating affected the surface, with fewer and smaller pores. At paper the coating of which was treated with ultrasound the surface was smoother and fewer pores were detected. The results showed that the ultrasonic treatment is not only an inexpensive and environmentally friendly process, but is also very effective in the preparation of solutions for bio-based coatings. Such coatings have better moisture resistance and are more flexible, which is important for packaging paper. Therefore, preparing solutions using ultrasound as pretreatment is an improved and convenient procedure to enhance many properties of bio-based coatings. [ABSTRACT FROM AUTHOR]

Paper with its mechanical strength as well as due to its microfluidic properties has emerged as an interesting sustainable material for future high-tech applications. Examples include paper-based sensors and actuators, paper-based construction materials and paper-based membranes. These examples have in common that a precise control of the water distribution inside the paper sheet during fluid water imbibition, water vapor adsorption, or drying affects the fluidic properties of the paper, which are crucial for its performance. Here silica-based coatings are applied to control the water distribution in the paper sheet during imbibition, adsorption and drying. By using dense silica coatings, the fibers are shielded from water penetration which limits the water distribution into the fiber–fiber voids. Whereas with a mesoporous silica coating, mesopores can be inserted into the paper, providing an additional space for water imbibition and adsorption. Water location upon imbibition, adsorption and drying were investigated using small angle x-ray scattering and gravimetric water vapor adsorption. Thereby, water distribution upon imbibition and adsorption depends on the type of silica coating. In addition, the drying mechanism and water distribution during drying is as well determined by the silica-based coating. The obtained results allow to deduce design criteria for local water management in paper sheets. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs) and chitosan (Cht) have been studied extensively for oxygen and water vapour barrier coatings in biodegradable, compostable or recyclable paper packaging. However, rare studies have been performed by using scalable, inexpensive, and fast continuous slot-die coating processes, and none yet in combination with fast' and high-throughput near-infrared (NIR) light energy drying. In this frame, we studied the feasibility of a moderately concentrated (11 wt%) anionic CNC and (2 wt%) cationic Cht coating (both containing 20 wt% sorbitol related to the weight of CNC/Cht), by using plain and pigment pre-treated papers. The effect of coating parameters (injection speed, dry thickness settings) were investigated on coating quantity (dry weight, thickness) and homogeneity (coverage), papers' structure (thickness, grammage, density), whiteness, surface wettability, barrier (air, oxygen and water vapour) properties and adhesion (surface strength). The coating homogeneity was dependent primarily on the suspensions' viscosity, and secondarily on the applied coating parameters, whereby CNCs could be applied at 1–2 times higher injection speeds (up to 80 mL/min) and versatile coating weights, but required a relatively longer time to dry. The CNCs thus exhibited outstanding air (4.2–1.5 nm/Pa s) and oxygen (2.7–1.1 cm3 mm/m2 d kPa) barrier performance at 50% RH and 22–33 g/m2 deposition, whereas on top deposited Cht (3–4 g/m2) reduced its wetting time and improved the water vapour barrier (0.23–0.28 g mm/m2 d Pa). The balanced barrier properties were achieved due to the polar characteristic of CNCs, the hydrophobic nature of Cht and the quantity of the applied bilayer coating that can provide sustainable paper-based packaging. [ABSTRACT FROM AUTHOR]

Absorption of liquid or vapor water in paper designed for conversion processes is a critical phenomenon. In particular, the dimensional stability of the paper as the water content changes is crucial for the success of all the conversion processes, including copying and printing. Appropriate chemical treatments of the fibers can limit the phenomena of water absorption, allowing a better workability of the paper substrates. In the present study, moisture absorption tests were conducted under isothermal conditions on untreated papers and treated by coatings with silane, organo-siloxane and silicone agents, as well as with polyelectrolytes using layer-by-layer techniques. The treated and untreated papers were tested by changing the relative humidity between 0 and 80% relative humidity. The Guggenheim–Anderson–de Boer model was used to study moisture absorption isotherms, showing the increase in the dimensional stability of the papers after the chemical treatments of the fibers. [ABSTRACT FROM AUTHOR]

Replacing nonbiodegradable plastics with environmentally friendly cellulose materials has emerged as a key trend in environmental protection. This study highlights the development of a strong and hydrophobic micro-nano fibrillated cellulose paper (MNP) through the incorporation of micro-nano fibrillated cellulose fiber (MNF) and chitin nanocrystal (Ch), followed by the impregnation of polymethylsiloxane (PMHS). A low-acid, heat-assisted colloidal grinding strategy was employed to prepare MNF with a high aspect ratio effectively. Ch was incorporated as a reinforcing matrix into the cellulose fiber scaffold through straightforward mechanical mixing and mechanical hot-pressing treatments. Compared to pure MNP, the 5Ch-MNP exhibited a 25 % improvement in tensile strength, reaching 170 MPa, and showed enhanced barrier properties against oxygen and water vapor. The impregnation of PMHS rapidly confers environmentally resistant hydrophobic properties to 1 % PMHS-5Ch-MNP, leading to a water contact angle exceeding 112°, and a 290 % increase in tensile strength under wet conditions. Additionally, the paper demonstrated excellent antibacterial adhesion properties, with the adhesion rates for E. coli and S. aureus exceeding 98 %. This study successfully produced functional cellulose paper with remarkable mechanical properties and barrier properties, as well as hydrophobicity, using a simple, efficient, and environmentally friendly method, making it a promising substitute for petroleum-based plastics. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The growing interest in paper-based materials for packaging is driven by their renewable and eco-friendly characteristics. However, their poor barrier performance against water, oil, and gas limits their application in the food packaging industry. In this study, we developed a simple dual-layer coating method to create water- and oil-repellent, gas barrier, antioxidant, and antibacterial paper-based materials using naturally-derived materials, including chitosan (CS), ethyl cellulose (EC), and cascade biorefinery products from green walnut husk (GWHE and CNC). The bottom CS/CNC oil-resistant coating and the top EC/GWHE water-resistant coating were applied to the paper surface. The synergistic effect of these coatings enhances the gas barrier and imparts functional properties to the paper. Compared to uncoated paper, the dual-layer-coated paper demonstrated a 239.1 % increase in tensile index, a higher kit rating value of 12/12, a lower Cobb 60 value of 3.21 mg/m2, a 44.0 % decrease in water vapor permeability (WVP), and a 90.7 % reduction in air permeability (AP). Additionally, this coated paper exhibited good antioxidant and antibacterial properties and favorable biodegradability. This study provides novel insights into the valorization of GWH waste and presents a sustainable strategy for producing high-performance paper-based materials for food packaging applications. [ABSTRACT FROM AUTHOR]

Regenerated cellulose and chitosan were deposited by self-assembly onto the surface of cellulose base paper to prepare an oil-resistant food packaging paper (ORFPP). The ORFPP exhibited favorable barrier properties to oil and water, and also had good mechanical properties and thermal stability. The cellulose base paper was coated with a 3 wt% solution of regenerated cellulose and then impregnated with a solution of chitosan. Optimum conditions were found to be a 3 min impregnation time, with two impregnations, in a 1 wt% impregnation solution (paper termed ORFPP (3−2-1)). The coated weight of the ORFPP (3−2−1) was 11.76 g/m2 and the oil resistance grade (Kit rating) was 11.6. The tensile index of the ORFPP (3−2−1) increased by 135.14 % and its performance as a barrier to water vapor increased by 78.54 %, compared with the base paper. This study paves the way for the preparation of new environmentally friendly food packaging materials. • A biomass-based eco-friendly oil-resistant food packaging paper was prepared. • Regenerated cellulose and chitosan were deposited onto base paper by self-assembly. • RSM was used to optimize the preparation of the oil-resistant food packaging paper. [ABSTRACT FROM AUTHOR]

In the packaging industry, petroleum-based polymers modify papers' barrier and surface properties. However, coatings of natural or modified biopolymers are an environmentally sustainable alternative. This study aimed to evaluate if biodegradable coatings based on natural rubber latex (NR), natural rubber latex cross-linked (CNR) by the photoinitiator Darocur 1173, cellulose microfibrils (CMFs), and phosphorylated cellulose microfibrils (PCMFs) improve the barrier properties of paperboard. Latex suspensions containing 5 % (m/m) of CMFs or PCMFs (based on latex solid content) were tested. The suspensions were evaluated regarding solid content, pH, and viscosity. The thickness, grammage, scanning electron microscopy (SEM), water vapor transmission rate (WVTR), water vapor permeability (WVP), water absorption capacity (Cobb 120 test), contact angle, wettability, and resistance to oils of coated paperboards were evaluated. The WVP for the NR/PCMFs (46.97 ± 0.74 g.mm/day.m2kPa) and CNR/PCMFs (47.89 ± 0.18 g.mm/day.m2kPa) coatings were 43 % and 42 % and below that of the reference paper. Regarding the contact angle, the coatings were hydrophobic (99.41 ± 1.66°). The wettability of the samples with CMFs or PCMFs was lowest (0.014 ± 0.002° s−1), except for the NR/PCMF treatment (0.103 ± 0.023° s−1). The formulations conferred maximum oil permeation resistance (oil kit 12). Latex crosslinking improved suspension dispersion homogeneity and the PCMFs' miscibility, improving the paperboard's barrier and surface properties. [Display omitted] • Phosphorylation pretreatment reduced energy consumption in the production of CMFs. • The crosslinking of the natural rubber latex was effective. • The penetration of water vapor into card paper was reduced with the application of formulations with PCMFs. • All formulations tested showed maximum oil permeation resistance. • Latex crosslinking improved suspension dispersion homogeneity and improved PCMFs miscibility in card paper. [ABSTRACT FROM AUTHOR]

[Display omitted] Soybean-oil-based polymer is a promising bio-based water barrier coating on paper packaging but the application is challenged due to its poor water dispersibility. In this present study, 3-aminopropyltriethoxysilane (APTES) modified nanocrystalline cellulose (NCC) was used to implement a stable dispersion of acrylated epoxidized soybean oil (AESO) in water and thus synergistically improved the water vapor barrier properties after coating on paper. APTES-NCC was successfully prepared, and displayed a better interface compatibility with AESO through the Michael addition reaction. Compared with NCC, APTES-NCC displayed an improved hydrophobicity and wettability with AESO, with an increase of contact angle from 38.0° to 76.4°, and a decrease of interfacial tension from 91.5 ± 3.5 mN/m to 82.9 ± 1.8 mN/m. As an emulsifier, APTES-NCC can be more effectively adsorbed on the oil–water interface to form a more stable emulsion than NCC, with a decrease of AESO droplets size from 4.8 µm to 3.1 µm, and a remarkable improvement in static and centrifugal stability. In rheological measurement, the APTES-NCC/AESO emulsion showed a wider linear viscoelastic region (3.4%), better viscoelasticity and thermal curing properties than that of NCC/AESO emulsion, which further explained that the stability of APTES-NCC/AESO emulsion were improved. Therefore, APTES-NCC/AESO emulsion as a coating on paper cured into a continuous barrier film can effectively improve the water vapor barrier properties of paper, and the water vapor transmission rate (WVTR) of paper can be reduced from 1392.8 g/m2•24 h (NCC/AESO emulsion-coated) to 1286.3 g/m2 24 h (APTES-NCC/AESO emulsion-coated), both are significantly lower than that of base paper (1926.7 g/m2•24 h). CLSM testing showed that APTES-NCC could interact effectively with AESO to forming a tight barrier on paper surface and at the same time, sealing the pores inside the paper to resist water vapor penetration. The high-stable AESO emulsion prepared by APTES-NCC is expected to facilitate the utilization of NCC and AESO as a value-added material in making sustainable barrier packaging. [ABSTRACT FROM AUTHOR]