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The food packaging characteristics and environmental impact of paper coated with polysaccharide dispersions were analyzed. Colloidal dispersions of xylan and xylan derivatives, as well as their combinations with chitosan and nanocrystalline cellulose, were applied in thin layers on both sides of the paper surface (5 g/m²). The barrier properties to water, water vapor, gases, oil/grease, and the antimicrobial properties of the coated paper were evaluated. Generally, polysaccharide coatings improved the barrier and antimicrobial features of coated papers compared to uncoated paper. Significant improvements were obtained by combining xylan derivatives and chitosan, where the contact angle of the coated paper reached 92.8° and achieved 100% inhibition of Bacillus sp. Furthermore, food simulant tests indicated that all tested polysaccharide combinations are suitable for use in food packaging, especially for fatty products. After 28 and 42 days of soil degradation, all samples of xylan and xylan/xylan derivatives/chitosan/nanocellulose coatings reached similar degradation levels (70 to 80% and 14 to 16 mg CO2 production). [ABSTRACT FROM AUTHOR]

The main objective of this research is to evaluate the influence of coating based on cellulose micro/nanofibrils (CMF) and carboxylated styrene butadiene rubber (XSBR) on sack kraft paper, for possible use in packaging. Filmogenic solutions were applied manually as a coating on sack kraft paper. These solutions were prepared by suspensions of CMF 1.5 % w/v with the addition of different content of XSBR (0, 2, 10, and 20 % about the total mass of CMF). Uncoated sack kraft paper was used as control. Films were obtained by casting and characterized physically, morphologically, and mechanically. The results demonstrated that XSBR and CMF composite suspension showed good performance as a coating on sack kraft paper. The formation of homogeneous structures well distributed on paper can be observed on scanning electron microscope images. Coatings containing XSBR presented a smoother surface, less porosity and hydrophilicity, and a greater coalescence, with good properties of air resistance and water vapor permeability. However, regarding mechanical properties, there were no improvements in coated papers. Therefore, the present study contributed information on the development of more flexible and hydrophobic cellulosic papers for possible applications in the industrial packaging sector. [ABSTRACT FROM AUTHOR]

Despite many technical challenges in the development of safe and environmentally friendly food packaging paper materials with excellent water and oil resistance using simple methods, producing paper-based functional materials using bio-based polymers is currently an important topic in the food packaging industry. In this study, novel water and oil-resistant coatings for the paper were developed through the combination of sodium alginate (SA), hydroxypropyl methylcellulose (HPMC), polyvinyl butyral (PVB), and hydrophobic silica nanoparticles (HSNPs). To impart oil-repellency to paper, SA and HPMC were first mixed uniformly and coated on the base paper, which was pre-treated with calcium chloride solution. A compact and tough coating layer was formed on paper due to the hydrogen bonding between SA and HPMC molecules, and the crosslinking between SA and Ca2+ ions in the base paper. High water resistance of the paper was achieved through the coating of PVB and HSNPs on top of the coating of SA/HPMC. The final coated paper demonstrated outstanding oil resistance (kit rating: 12/12), water resistance (Cobb value: 4.23 g/m2), low water vapor transmission rate (100 g/m2·24 h), and improved mechanical properties. This fluorine-free, and biodegradable barrier paper will find excellent applications in the food packaging industry. [Display omitted] • SA and HPMC as the first coating, PVB and HSNPs as the second coating gave the paper excellent water and oil resistance. • The water and oil-resistant paper materials showed excellent barrier properties and improved mechanical properties. • The water and oil-resistant paper materials were fluorine-free and biodegradable. • The preparation process was convenient. [ABSTRACT FROM AUTHOR]

In an organic circular economy, biodegradable materials can be used as food packaging, and at end-of-life their carbon atoms can be recovered for soil enrichment after composting, so that new food or materials can be produced. Packaging functionality, such as mechanical, gas barrier, and heat-seal performance, of emerging biodegradable packaging, with a laminated, coated, monomaterial, and/or blended structure, is not yet well known in the food industry. This lack of knowledge, in addition to end-of-life concerns, high cost, and production limits is one of the main bottlenecks for broad implementation in the food industry. This study determines application areas of 10 films with a pragmatic approach based on an experimental broad characterization of packaging functionality. As a conclusion, the potential application of these materials is discussed with respect to industrial settings and food and consumer requirements, to support the implementation of commercially available, biodegradable, and, more specifically, compostable, materials for the identified food applications. [ABSTRACT FROM AUTHOR]

The usage of bio-based polymers to construct paper-based functional materials is currently an important topic in the food packaging industry. Nevertheless, the facile and effective construction of packaging paper materials with excellent water and oil repellency, self-cleaning property, biodegradability and recyclability currently faces distinct challenges. In this aspect, we have developed a one-step coating method for preparing hydrophobic and grease-resistant paper basing on templating dichloromethane-in-water (O/W) cellulose nanocrystals-stabilized Pickering emulsions, which contain chitosan (CS) and glutinous rice starch (GRS) in water phase and polylactic acid (PLA) in oil phase. Herein, the greaseproof polysaccharides CS and GRS are served as the coating film matrix, where the hydrophobic PLA is embedded in the form of microspheres. The optimized coated paper with rough surface structure display highly hydrophobic and water barrier properties with the water contact angle of larger than 130° and water vapor transmission rate of 3.57 × 10−10 gm−1s−1Pa−1, outstanding oil resistance with the kit rating of 9.5/12 and self-cleaning performance. Most interestingly, the soil burial test shows the favourable biodegradability of the coated paper. In addition, the pulp can be recycled from the coated paper and then reused to make paper, validating the recyclability of the coated paper. This study provides a new sustainable and universal research strategy for the large-scale preparation of fully bio-based, recyclable, hydrophobic and oil-resistant, self-cleaning, biodegradable paper materials, which exhibit the highly promising applications in food packaging industry. [Display omitted] • Pickering emulsion template is used to one-step prepare packaging paper coatings. • Water and oil resistance of paper clearly increased after coating treatment. • Coated paper displays excellent biodegradability and self-cleaning performance. • •Coated paper can be recycled by a simple recycling process. • Coated paper shows promising potential application in food packaging. [ABSTRACT FROM AUTHOR]

The work presented in this paper is focussed on study of structure and properties of coating layers based on natural pigments (ground calcium carbonate and clay) and butadiene acrylonitrile latex as binder in correlation with functional properties of the final coated paper. It is quantified the influence of binder content and pigment type on the structural and liquids penetration properties of coating layer. The obtained results confirm that by increasing of binder content in the coating formulations a reduced efficiency of light-scattering and increased roughness for coated surfaces is obtained. At the high binder amounts (over 15 pph), the coating layer porosity is reduced and as result a lower liquids penetration in the coated papers is obtained. [ABSTRACT FROM AUTHOR]

With the increasing popularity of coated paper, it has been more widely used in printing, publishing, product packaging and commercial promotion. However, coated paper is prone to cracks after printing and folding which exposes to a white area which is referred to as fold cracking. This study investigated the coating properties of paper and coating factors influencing the fold cracking and aimed to provide guidance on how to reduce the problems of fold cracking. This paper mainly discusses the effects of pigment proportion, binder dosage, solids content, coating thickness and calendaring pressure on fold cracking of coated paper after printing. Experiments show that when the coating consisted entirely of calcium carbonate, the degree of fold cracking is most serious. With the addition of kaolin, the fold cracking reduces. When the ratio of the number of parts of calcium carbonate to kaolin is 25/75, the area of fold cracking reaches its minimum value of 10.28 %. With increasing solids content of the coating, the fold cracking decreases initially and then increases. When the solids content is 55 %, the fold cracking reaches a minimum. Increased latex content reduced coating thickness and an increase in calendaring pressure gradually reduce the degree of fold cracking. [ABSTRACT FROM AUTHOR]

The coating technique, supposedly invented by Chinese papermakers no later than the 3rd century AD, greatly improved paper sheets' qualities of color, texture, writability, and printability. Alongside the dispersal of papermaking and surface-treatment techniques beyond China, coated papers were manufactured and used in many other regions of the world. Understanding the manufacture of coated papers, therefore, is crucial for perceiving how surface treatments were developed to meet the need for paper with enhanced properties. However, the characterization of coating and coating pigments on ancient Chinese papers has long remained an unsolved issue, and previous studies on this topic have often produced inconclusive results. To explore a non-invasive methodology that can more reliably characterize coated papers and the coating pigment on them, this article presents the results of a pilot study that applied micro-computed tomography (micro-CT) and Raman spectroscopy to samples of three Qing Dynasty (1644–1911 AD) papers and two handmade papers manufactured in China in the 1990s. Micro-CT revealed the coating layer(s) on Lajian (waxed coated paper) and Lengjinjian (gold-dusted paper) of the Qing Dynasty and characterized the modern raw xuan and bamboo papers as uncoated. Raman spectroscopy, together with handheld X-ray fluorescence analysis, identified the mineral-based pigment in the coating layer, suggesting the use of lead white or kaolin as the coating pigment. Additionally, Raman analysis confirmed the use of other mineral pigments (red lead and cinnabar), beeswax, and organic dyes (gamboge, kermesic acid, and possibly purpurin) in the manufacture of Lajian and Lengjinjian papers. The combination of micro-CT and Raman spectroscopy, it is therefore suggested, is a practical, more reliable approach for non-invasive investigation of coating and coating pigments on ancient Chinese paper specimens. [ABSTRACT FROM AUTHOR]

Upcycling agroindustry residues into new valuable products is a strategy for mitigating environmental impacts while increasing material circularity. In this study, two sizes of eggshell particles (D 90 = 7.1 μm (ESAJ) and D 90 = 16.3 μm (ESBU)) were obtained and their incorporation as fillers into biodegradable pectin/starch film was evaluated. The effect of the presence of eggshell particles (2–8 w/w%) on the structural and morphological aspects, water barrier, and mechanical, optical, and thermal properties of the biocomposites was evaluated and then the reinforced film was applied on the surface of kraft paper. The release of calcium in an acidic solution was inverse to the size and concentration of particles and the released íon may contribute to the crosslinking of pectin. The incorporation of only 2 % eggshell resulted in 42% lower solubility of the film. The eggshell-reinforced films proved to be more opaque and rigid. The addition of 6% ESAJ significantly improved the tensile strength (an increase of 32%), modulus of elasticity (an increase of 29.7%), and water vapor barrier (59% of improvement). DSC analysis suggests that the calcium from the eggshell interacts with the pectin polymeric structure, reducing the sites available for water molecules, which may have caused more mobility of the chains through the matrix. The reinforced pectin/starch film was very well adhered to the kraft paper in the application test by continuous casting, but the coated paper showed no improvement in oil and water resistance, which means that other coating processes need to be explored. • Eggshell was used as a reinforcing filler material in pectin/starch film. • Eggshell particles were well adhered to the matrix. • The eggshell powder had improved the water resistance of the pectin/starch film. • The addition of 6% eggshell had increased the film's tensile strength in 32%. [ABSTRACT FROM AUTHOR]

The pore structure of the coating layer is one of the most important factors in determining the printability of coated papers. The coating pigment and binder are two principal components in paper coating, and their characteristics have a critical influence on the coating structure. The glass transition temperature (Tg) of latex binders affects the mechanical strength and pore structure of the pigment coating layer because the latex Tg influences the binding ability of latex and the shrinkage of the coating layer during the drying process. In this study, styrene-acrylate (S/A) core-shell structure latexes with different monomer compositions in the core and shell layers were designed, and their properties were compared with those of a conventional latex. These core-shell latexes were prepared using the same monomers in the same proportion and were used to investigate the effect of the core-shell structure on the structural and mechanical properties of the coating layer. The hard-shell latex with a high styrene content in the shell part yielded paper that was glossier and less rough and formed finer pores, resulting in an increased ink absorption rate into the coated paper compared to the other types of latex. The hard-shell structure showed better performance in printing uniformity and had less mottling. [ABSTRACT FROM AUTHOR]

The paper aging is primarily attributed to the presence of carbonyl groups formed as a result of the oxidation of the hydroxyl groups at the second and third carbon atom in the elementary unit of the cellulose macromolecule and the presence of both aldehyde and carboxyl groups in the cellulose materials. Reduction of paper whiteness degree is mainly connected with the presence of lignin, hemicelluloses, the presence of metals and the sizing agent type. The paper as an elasto-plastic, capillary porous material quickly breaks down at an elevated temperature. The latter accelerates the chemical reactions that occur in paper in the course of aging. The depth of the paper changes depends not only on the temperature but also on the duration of the impact. For different paper types differing in composition the reaction rate constant is different. Its temperature dependence is described by the Arenius equation. The aim of this work is to carry out a kinetic analysis of the influence of the temperature increase on the ageing of coated paper used for book covers. The accelerated thermal aging is conducted at three different temperatures - 90°C, 105°C and 120°C with duration of 6 h, 12 h, 18 h, 36 h and 48 h. In order to examine the kinetics of the process the level of whiteness is determined. The data obtained from the thermal aging of the paper are treated using the laws of polychrome kinetics. [ABSTRACT FROM AUTHOR]

Expensive synthetic coating materials can be replaced with natural coatings and surface treatment with natural components and additives which are friendlier to the environment and have normally better special surface properties. However, special properties can be obtained with surface functionalization by chemical or surface geometry modification. Beside optical properties, the trends of lightweight materials, i.e. reducing grammage by using nano materials and products (i.e. NMP - N-Methyl-2-Pyrrolidone), lower specific energy requirement and costs, forces increasing of pigments usage. Results of survey showed that surface properties of papers coated with modified ground calcium carbonate (GCC), required for inkjet printing with water-based inks had improved significantly, whereas the increment of printed object has minimum differentiation from the ideal, computer-based character. [ABSTRACT FROM AUTHOR]

Paper-based packaging materials have seen explosive growth in recent years as consumers become more aware of the environmental and health hazards created by traditional food packaging materials. Even yet, there is a significant opportunity for improvement in the production of fluorine-free, water- and oil-proof, recyclable food packaging papers made from ecologically friendly polymers. In this study, we used sodium alginate (SA), cellulose nanofibers (CNF), ethyl cellulose (EC), and polyvinyl butyral (PVB) to create coatings that are impervious to water and oil. The paper was first impregnated with CaCl 2 solution before SA and CNF were evenly mixed and applied to the paper. Ca2+ ion cross-linking strengthened the connection between the SA/CNF coating and the paper, which increased its oil-proof properties. The hydrogen bonding force in EC/PVB solution enhanced the water-proof performance and mechanical qualities of the paper. Finally, the water- and oil-proof paper showed excellent water repellency (Cobb value: 1.1 g/m2), oil repellency (kit rating: 12/12), low air permeability (0.2 µm/Pa·s), and stronger mechanical properties (4.21 kN/m). There is a great need for this fluorine-free, biodegradable, and recyclable paper-based material in the food packaging market due to its excellent barrier qualities. [Display omitted] • SA and CNF as the first coating give the paper excellent oil resistance. • EC and PVB as the second coating impart excellent water resistance to the paper. • The paper materials are fluorine-free, recyclable, and biodegradable. [ABSTRACT FROM AUTHOR]

Due to the increasingly serious environmental and human health hazards brought by traditional food packaging materials, paper-based packaging materials have become increasingly popular among consumers in recent years. Currently, the fabrication of fluorine-free degradable water- and oil-repellent paper using low-cost bio-based polymers by a simple method is a hot subject in the field of food packaging. In this work, we used carboxymethyl cellulose (CMC), collagen fiber (CF), and modified polyvinyl alcohol (MPVA) to create coatings that were impervious to water and oil. The homogeneous mixture of CMC and CF generated electrostatic adsorption to impart excellent oil repellency to the paper. PVA was chemically modified by sodium tetraborate decahydrate, and the MPVA coating imparted excellent water-repellent properties to the paper. Finally, the water- and oil-proof paper showed excellent water repellency (Cobb value: 1.12 g/m2), oil repellency (kit rating: 12/12), low air permeability (0.3 μm/Pa·s), and stronger mechanical properties (4.19 kN/m). This non-fluorinated degradable water- and oil-repellent paper with high barrier properties prepared by a convenient method is expected to be in widespread use in the food packaging field. [Display omitted] [ABSTRACT FROM AUTHOR]

Paper used in the printing industry generally contains a relatively thin porous coating covering a thicker fibrous base layer. The three-dimensional pore structure of coatings has a major effect on fluid flow patterns inside the paper medium. Understanding and quantifying the flow properties of thin coating layers is hence crucial. Pore spaces within the coating have an average size of about 180 nm. We used scanning electron microscopy combined with focused ion beam (FIB-SEM) to visualize the nano-scale pore structure of the paper coating layer. Post-processing of the FIB-SEM images allowed us to reconstruct the three-dimensional pore space of the coating. The 3D FIB-SEM images were analyzed in detail to obtain pore size distribution and porosity value. The permeability was estimated using the GeoDict software, based on solutions of the Stokes equation. By determining the porosity and permeability of increasingly larger domain sizes, we estimated the size of a representative elementary volume (REV) for the coating layer to be 60 µm 3 , which is well within the volume analyzed using FIB-SEM. The estimated porosity and permeability of the REV domain were 0.34 and 0.09 mDarcy, respectively. Using the pore morphology method, capillary pressure-saturation ( P c - S ) and relative permeability curves of the REV domain could be constructed next. The P c -S curves showed that the coating had a high air entry suction, which is very favorable for printing in that ink will invade the coating as soon as it is applied to the coating. Our results are essential for macroscale modelling of ink penetration into a coating layer during inkjet printing. Macroscopic models can be valuable tools for optimization of the penetration depth and the spreading of ink on and within paper substrates. [ABSTRACT FROM AUTHOR]

During the folding process substrates are exposed to high-localized stresses, which in the case of coated papers and boards, can lead to decreased aesthetic features or complete loss of functionality. Production efficiency of the folding process could be improved by an automated, computer vision-based inspection system. For such a task, different existing computer-aided fold-crack evaluation approaches were analyzed. A detailed research was conducted to propose an image processing based fold cracking assessment via finding optimal sample preparation and digitization techniques and developing an algorithm for the digital image analysis and feature extraction. The analysis of the applicability of different sample preparation and digitization parameters, as well as the proposed digital image feature, was done by correlation evaluation, one-way analysis of variance (ANOVA) and corresponding post hoc tests. The results indicated that the developed algorithm fulfils the set requirements and the proposed feature of digitized samples faithfully describes the analyzed fold-cracks. [ABSTRACT FROM AUTHOR]

Environmentally friendly flexible materials with functionalities such as reversibly tunable wettability have become much sought after because of their great potential for biological, chemical and electronic applications. We prepared a flexible superhydrophobic material by coating the hydrophobic nano-TiO 2 particles on lignocellulosic paper. The coated paper surfaces exhibited a reversible switching between superhydrophobicity and superhydrophilicity through UV irradiation and heating, respectively. After the UV irradiation treatment for about 100 min, the wettability of the coated paper is switched from superhydrophobicity to superhydrophilicity. After the coated paper with superhydrophilicity is heated for 25 h, the water contact angle (WCA) recovers to the original superhydrophobic state. Compared to the literatures, the switching time between two kinds of superwettability is significantly reduced. SEM images and XPS spectra indicate that the change in chemical composition of the coated paper surface is responsible for the reversible switching of wettability. The coated paper developed in this study is an attractive smart material with reversibly switchable wettability which has significant potential application in many fields which require tunable wettability. • A simple and practical approach to prepare superhydrophobic paper by roll coating with modified nano-TiO 2. • The coated paper surfaces exhibited a reversible switching between superhydrophobicity and superhydrophilicity through UV irradiation and heating, respectively. • After the UV irradiation treatment for about 100 min, the wettability of the coated paper is switched from superhydrophobicity to superhydrophilicity. • After the coated paper with superhydrophilicity is heated for 25 h, the water contact angle (WCA) recovers to the original superhydrophobic state. [ABSTRACT FROM AUTHOR]

Paper is widely used as food packaging because of good mechanical strength and degradability. However, the application scope of paper is limited by a relatively strong affinity for water and oil. In this study, we prepared two types of coated paper and investigated the influence of the air permeability and polarity on the oil resistance of the coated papers. Reducing the air permeability improved the grease resistance of the coated papers. High-surface-energy coatings exhibited enhanced oil resistance because of a high content of polar components that offered high resistance to grease. The mechanical properties of the paper were also improved by applying the coating. These naturally derived materials are an alternative to the fluoride-containing materials that are currently available on the market for improving the wettability of paper and the quality and safety of grease-rich foods. • The oil resistance of cellulose food packaging paper are positively related to the coating weight. • The oil resistance of cellulose food packaging paper is positively related to the polarity of the coating. • Even with relatively low coating weight, the coating with high polarity still has good oil resistance. [ABSTRACT FROM AUTHOR]

This study aims to develop a high-performance delivery system using microfibrillated cellulose (MFC)-coated papers as a controlled release system combined with the well-known drug delivery agent, β-cyclodextrin (βCD). Chlorhexidine digluconate (CHX), an antibacterial molecule, was mixed with a suspension of MFC or a βCD solution or mixed with both the substances, before coating onto a cellulosic substrate. The intermittent diffusion of CHX ( i.e. , diffusion interrupted by the renewal of the release medium periodically) was conducted in an aqueous medium, and the release mechanism of CHX was elucidated by field emission gun-scanning electron microscopy, SEM, NMR, and Fourier transform infrared analyses. According to the literature, both βCD and MFC are efficient controlled delivery systems. This study indicated that βCD releases CHX more gradually and over a longer period of time compared to MFC, which is mainly due to the ability of βCD to form an inclusion complex with CHX. Furthermore from the release study, a complementary action when the two compounds were combined was deduced. MFC mainly affected the burst effect, while βCD primarily controlled the amount of CHX released over time. In this paper, two different types of controlled release systems are proposed and compared. Depending on the final application, the use of βCD alone would release low amounts of active molecules over time (slow delivery), whereas the combination of β-cyclodextrin and MFC would be more suitable for the release of higher amounts of active molecules over time (rapid delivery). [ABSTRACT FROM AUTHOR]

Wetting of coated papers by isopropyl alcohol (IPA)-based fountain solutions or surfactant solutions was studied in this paper. Additionally, the effect of paper surface properties on wetting was analyzed. To that end, six fountain solutions were prepared. Three solutions had increasing amounts of IPA, and three were made from surfactant-based dampening agents. Eight commercial coated papers were selected and characterized in terms of roughness and surface free energy. Paper resistance to wetting by fountain solutions was evaluated by measuring the static and dynamic contact angles. Static contact angles between the paper surface and the IPA-based fountain solutions decreased as the alcohol concentration increased, whereas the wettability with surfactantbased fountain solutions was highly dependent on their surface tensions. Paper surface free energy strongly affects the static contact angle and only moderately affects the dynamic contact angle. [ABSTRACT FROM AUTHOR]

Highlights: [•] RH-triggered tuning of the size of micro-cracks in protein coated paper. [•] Gas permeation of protein coated paper suitable to eMAP of parsley at 20°C/80% RH. [•] 72% of chlorophyll and 52% of vitamin C remain in parsley after 8days under eMAP. [ABSTRACT FROM AUTHOR]

Many kinds of adhesives are used to produce paper and prints. However, it is difficult to observe the distribution of these adhesives in situ because most are transparent and of low content. We have developed a fluorescence staining technique, which observes adhesives in paper with a confocal laser scanning microscope (CLSM) after staining with specific fluorescent dyes. In this review, we present our observations using this technique on a wet strength resin in paper, the vehicle of offset printing ink on uncoated paper, and the coating binder in coated paper. The polyamide epichlorohydrin (PAE) resin, a wet strength resin, was selectively stained with Sulforhodamine 101 acid chloride, while the pulp fibers were stained with Acridine Orange. The distribution of PAE could be observed in a CLSM fluorescence image at the excitation wavelength of 543 nm, and the pulp fibers could be observed in a fluorescence image at the excitation wavelength of 473 nm. From this it was found that PAE tends to concentrate at fiber crossings. In order to quantify the penetration of the ink vehicle into the base paper sheet, cyan offset inks stained with Rhodamine B were printed on various paper samples. The location of the vehicle was determined with CLSM. The penetration of the ink vehicle was observed in three-dimensional images. Coated papers were soaked in a solution of Rhodamine B in ethanol, and then they were rinsed with pure ethanol. The styrene-butadiene latex of the coating binder was selectively stained with Rhodamine B. The distribution and position of latex in the coating layer was characterized with CLSM. [ABSTRACT FROM AUTHOR]

Abstract: Freshness of common mushrooms was related to the internal atmosphere composition during modified atmosphere packaging (MAP) experiments at 20°C and 80% RH with stretchable polyvinylchloride (PVC) film, paper, and the same paper coated with a wheat gluten solution. MAP with the stretchable film led to a detrimental deterioration of mushrooms after only one day of storage: dark brown blotches appeared and almost 30% of mushrooms exhibited open veil. This was due to the formation of condensed water at the inner surface of the material and onto mushrooms combined to a high O2 partial pressure (16kPa) in the headspace. Wheat gluten (WG) coated paper was the most effective to improve the shelf-life of mushrooms since it allowed the preservation of a fair colour, unbroken veils, and an acceptable texture during 3days. This beneficial effect was attributed to the combination of a medium CO2 (9.5kPa) and low O2 (2.5kPa) partial pressure, without condensation. The main drawback of using WG-coated paper was its high water vapour permeability that led to an important weight loss (3.8wt.% on day 3). However it did not affect the overall quality of mushrooms within the storage duration. Industrial relevance: Even with the development of micro-perforated materials that provide the largest range of O2 and CO2 permeability values, several limitations are still encountered for synthetic MAP applications such as [–] an insufficient perm-selectivity ratio that remains lower than 6 (value of 1 for micro-perforated material): generated atmosphere cannot reach both low O2 and low CO2 partial pressures and then are not adapted to CO2-sensitive fresh produces. [–] unattractive water condensation at the inner surface of the packaging that might occur due to a low water vapour permeability, favouring the development of microorganisms. [–] their non biodegradability. Previous studies reported a high selectivity ratio and a high water vapour permeability for biodegradable materials made from crops proteins (wheat gluten, for instance) that appeared well adapted for fresh fruits and vegetables preservation. However, despite low cost and such interesting functional properties, these materials exhibited poor mechanical properties and cannot be used as packaging material. Combination with other materials, such as cellulosic fibres, appeared to one way to get round this major drawback without losing its biodegradability. Indeed paper exhibits an environmental-friendliness potential (recyclability, sustainability, biodegradability, and compostability) and a high versatility in food packaging. By choosing common mushrooms, known to be sensitive to high CO2 content, and a stretchable PVC film, commonly used to over-wrap mushrooms in tray (on European market), we demonstrate that this material was greatly less effective than a new biobased material (wheat gluten film coated onto paper) developed in collaboration with Smurfit Worldwide Research Center. This work confirms the interest in developing functionalised paper based packaging material with agro-based polymers adapted to the storage of fresh fruits and vegetable storage in ambient temperature. [Copyright &y& Elsevier]

The phenomenon of 'wet pick' during printing is well known to paper coating and printing technologists. Recent work has highlighted the reversible effect of water on the tensile strength of coating layers, and has shown that the mineral and vegetable oils commonly used in ink formulations have a similar, if smaller, detrimental effect on strength. In this study, we show that the coating strength decreases as the dielectric constant of the penetrating fluid increases. In the adhesive science literature, a similar correlation has been observed for various types of adhesive joints, and can be explained in terms of ion-pair bonding. We have tested this theory for mineral-based paper coatings containing latex adhesive, and found that it underestimates the loss of strength observed experimentally. In the latex–mineral bond, contributions from other mechanisms such as van der Waals forces are also likely. This knowledge should ultimately allow the design of more effective pigment–binder combinations better able to withstand weakening in the presence of fluids used in printing. [ABSTRACT FROM AUTHOR]

Abstract: A fluorescent chitosan derivative was deposited layer-by-layer onto conventional paper sheets and its distribution, in terms of both spreading and penetration, was assessed by SEM observations and emission measurements. The results showed that, on the one hand the surface distribution was highly homogeneous and, on the other hand, the penetration of chitosan within the paper pores ceased after a three layer deposit, beyond which any additional coating only produced an increase in its overall thickness and film-forming aptitude. These results show that this modified chitosan can be used as probe to optimize and understand the mechanism of the deposition of chitosan onto paper and other substrates. [Copyright &y& Elsevier]

Abstract: Many tests are known for testing the grease barrier performance of coatings in paper or paperboard. Some are manifested in standard procedures such as TAPPI, ASTM, or ISO, but as many procedures were developed and modified by companies and research groups. Mainly the test methods are based on visually detecting the amount of oil, which is in most cases dyed for better contrast, penetrating through the coating, meaning the procedures are based on a subjective visual evaluation and thus often not linked for instance to a statistical meaningful physical value. We found that by using a slightly modified ASTM D 722 test the L*a*b* color coordinates determined with a commercial handheld spectrophotometer are related to the grease barrier performance of an organic coating. By applying this new method the penetration time of an oil/dye mixture could be correlated to the lightness L* and chromaticity b* and fitted by an exponential function. Furthermore, the coating was slightly modified and an improvement or worsening of the grease barrier could be detected clearly outside of the statistical scatter of a control series. We call this method semiquantitative, since the level of grease barrier of a coating is not measured directly by a quantitative value, but color coordinates are correlated in a series to the effectiveness of the grease barrier. [Copyright &y& Elsevier]

Abstract: Biopolymers have the potential to serve as coating materials for paper to improve its performance properties. The objectives of this study were to determine the effect of hydroxypropyl methylcellulose (HPMC), glycerol (Gly) and beeswax (BW) coatings on the physical properties and water vapor permeability (WVP) of coated papers. It was found that HPMC coated paper showed significant differences on physical properties, compared with uncoated (p ⩽0.05). Folding endurance of HPMC-based coated papers greatly increased which indicated improved durability of coated paper. Moreover, HPMC-based coated papers increased in stretch and decreased in tensile index. HPMC-based coatings reduced WVP and further reduction was obtained when beeswax was incorporated in the HPMC-lipid composite coated paper. Paper coated with hydrocolloid and lipid can be used to produce packages with the potential to be used to maintain agricultural produce quality for the food industry, and may have other applications (i.e., medical packaging). [Copyright &y& Elsevier]

Abstract: The design of minerals for coated papers to maximise ink hold out and printed colour density has been an area of much study over the years. It is desirable in terms of cost and press runnability to achieve the required colour density with the minimum amount of ink applied. In this work, a series of heatset offset ink components was printed separately onto a coated paper and then combined into a varnish and then a whole ink. The ink components were visualised by focused ion beam (FIB) to determine which of the ink components entered the coating layer. The ink varnish was also applied to modified thin layer chromatography (TLC) plates, which had been coated with the same coating formulation as the paper samples. The separation of the ink components on modified TLC plates was assessed using FTIR spectroscopy. The results show that ink components, which enter the coating layer after offset printing, can be visualised in the FIB instrument. An exception to this was the mineral oil, which did not remain in the coating layer after drying and placing under vacuum due to its volatile nature. It was noticed that the contrast of the FIB image increased significantly when the samples with wax dissolved in the oil were imaged, which also allowed for a very clear imaging of the porous structure of coating layer. This type of image would be excellent for fundamental studies of detailed pore structure within a coating layer. This work agrees with other published findings which show that the pigments and hard resins remain on the surface of the coating, whereas the mineral and vegetable oils are mobile and penetrate into the coating layer. Ester solvent and dissolved wax also penetrate into the coating layer. [Copyright &y& Elsevier]

Time-of-Flight Secondary ion mass Spectrometry (ToF-SIMS), in conjunction with Principal Component Analysis (PCA), has been used to characterize the spatial distribution of the chemical components of ink, both on the surface and in the Z-direction of coated papers. Preliminary work was performed on commercial ink-jet printing paper and on commercially available photopaper to establish that ToF-SIMS, in conjunction with PCA, could help characterise ink/coating distribution. To illustrate further that ToF-SIMS/PCA could differentiate the individual components making up the ink, pigment-based and dye-based inks were applied to two coated papers (PCC + SA and PCC + starch + PVA) using an inkjet printer. This approach shows that high spatially resolved images obtained by ToF-SIMS allows a depth profile to be obtained, thereby allowing the correlation between ink distribution at the surface and in the Z-direction to be evaluated in relation to the coating formulation. [ABSTRACT FROM AUTHOR]

The need for good quality paper for dye sublimation transfer printing has been reported previously as a principal requirement for the process. Pigmented coated papers have gained acceptance in the traditional paper printing industry, but, despite their importance, have inspired very few reports in literature about their application in heat transfer printing. In the current work, we studied the influence of both clay and ground calcium carbonate (GCC) pigments and the incorporation of plastic pigment on the surface structure and mechanical properties of the coated paper used for transfer printing. The results showed that paper coating significantly reduced the surface roughness of the paper. The mechanical properties of the prepared coated paper, including tensile strength, stretch, tensile energy absorption (TEA), and burst index, were improved when coated compared to those of uncoated paper. The addition of plastic pigment to the coating mixture helped improve the paper's properties. The optical density of the transfer-printed polyester fabric using the prepared coated paper was also compared with that of uncoated paper. It was shown that a slight increase in optical density was evident in the coated paper. The possibility of producing a second polyester print from the exhaust paper was also investigated. Coated paper incorporating plastic pigment, in particular, showed higher optical density than did uncoated paper. We found that coated paper based on clay, GCC, clay/plastic pigment, or GCC/plastic pigment consumed less dye paste than uncoated paper though producing printed fabric with higher optical density - especially in the second print. [ABSTRACT FROM AUTHOR]

Abstract: Wheat gluten (WG), calcium caseinate (CC) and corn gluten meal (CGM), were selected as protein raw material to prepare coating solutions. Different concentrations of protein (10–20%, w/w) and deposited solution layer (50–500μm) were used to obtain coated papers with thicknesses varying between 143(±3) and 227(±8)μm. As expected, the thicknesses of coated paper increased with coating weight, but, for a given coating weight, different thicknesses were observed according to the raw material used and its concentration in the coating solution. A phenomenon involving a penetration of coating solution inside paper was suspected with WG-based solutions. The microstructure of coated papers was analyzed by SEM, OM and AFM and differences in structure and morphology were observed between the three raw materials. The percentages of coating agent impregnated inside paper were also calculated from the apparent density of coated paper and the density of self-supported films prepared in the same conditions but deposited on an inert and smooth Plexiglas® support. These percentages of impregnation ranged from 4.8 to 63.3% and increased as following: CC

The dielectric constant ε' and dielectric loss ε" of paper sheets coated with a clay-based mixture were measured within the frequency range 10² -105 Hz at room temperature. Various soluble thickeners were added separately to the coating mixture such as: three grades of carboxymethylcellulose (CMC) with different degrees of substitution (0.46, 0.67, and 1.31 DS), casein, and oxidized starch. Their effect on the dielectric behavior of coated paper was studied. The coated paper samples were printed using the rotogravure method. Printing evaluation was carried out by measuring print gloss. The aim of this work was to find out to what extent the dielectrical properties and printability of coated paper will be affected by the addition of soluble thickeners to a coating mixture. The results indicated that coating base paper with a clay-base mixture improved print gloss and increased both ε' and ε". By adding CMC, both paper and print gloss were improved and their effect increased as the degree of substitution was increased. ε' and ε" were decreased as the degree of substitution was increased due to decrease of hydroxyl groups by carboxymethylation. Casein and oxidized starch improved print gloss, but were less effective than CMCs. ε' and ε" decreased in the order casein < oxidized starch. It was concluded that,although the selected thickeners improved print gloss of the coated paper, they led to decreases of ε' and ε". [ABSTRACT FROM AUTHOR]

A better understanding of the parameters associated with heating of the coated paper during drying process would permit a more accurate design and control of the process to achieve an improved coated paper quality and printability. Following the application of the coating, the coated paper passes through non-contact dryers (i.e. infrared dryers and impinging hot air dryers). When the coating has coalesced, further drying is achieved with steam-heated, contact dryers. One parameter affecting the heat transfer from a metallic dryer drum to the coated paper is the thermal contact conductance at the interface between the coated paper and the drum. In this paper, the thermal contact conductance of a coated paper/metal interface is determined and compared to that of the uncoated paper. Two types of base stock and one type of coating are considered. The thermal contact conductance values are given as a function of the applied interface pressure. [ABSTRACT FROM AUTHOR]

Imparting electro-conductivity to cellulosic paper may allow this conventional material to hold great promise for a wide range of applications. In this work, polyaniline/cellulose nanocrystal (PANI/CNC) composite was prepared via emulsion polymerization and subsequently used as a conductive and reinforcing pigment for paper coating fabrication. Initially, the microstructure and properties of the fabricated PANI/CNC composite were comprehensively characterized. Furthermore, the effect of the PANI/CNC composite on the properties of paper coatings and coated paper was systematically investigated. The results showed that the viscosity and viscoelasticity of paper coatings were increased as a function of the PANI/CNC composite addition. Meanwhile, the increased CNC ratio in PANI/CNC composite led to the decreased viscosity and viscoelasticity of paper coatings. Furthermore, surface coating application was found to impart desired electro-conductivity and enhanced mechanical properties to coated paper. Compared to the coated paper without PANI/CNC composite, the coated paper with 4 wt% CNC added PANI/CNC composite maintained an electro-conductivity of 4.0 S·m−1 and exhibited increases of 14.6%, 30.7% in tensile index and folding strength, respectively. In particular, the electro-conductivity and mechanical properties of coated paper were also enhanced with the increased ratio of CNC in PANI/CNC composite. [Display omitted] • PANI/CNC composite was designed/prepared for paper coating application. • Electro-conductive paper was produced via surface application of PANI/CNC composite. • PANI/CNC composite led to increased viscosity and viscoelasticity of paper coatings. • PANI/CNC composite imparted conductivity and improved properties to coated paper. [ABSTRACT FROM AUTHOR]

Here, we report a non-toxic method for improving the oil-resistant performance of chitosan coated paper by coating the mixture of chitosan and montmorillonite (MMT) instead of coating chitosan solution only. Through combining MMT into the chitosan coatings, the coated paper exhibited a lower air permeability and enhanced oil resistance under a lower coating load. For coated papers C2.5 and C3 by coating 2.5% (w/v) and 3% (w/v) chitosan without adding MMT in the chitosan coating, the coating load was 3.76 g/m2 and 3.99 g/m2, respectively, and the kit rating values were only 7–8/12. Regarding the sample C2M0.1 coated by the mixed solution containing 2% (w/v) chitosan and 0.1% (w/v) MMT, its coating load was only 3.65 g/m2, the paper permeability after coating was reduced to 0.00507 μm/Pa·s, owing to the filling of MMT into the cellulosic fibers network, and the kit rating reached 9/12. Moreover, C2M0.1 showed improved mechanical properties, whereby its tearing resistance was 5.2% and 6.6% higher than that of the uncoated paper in the machine direction and the cross direction, respectively. [ABSTRACT FROM AUTHOR]

• Confocal laser microscopy was integrated with electron microscopy to visualize liquid inside nano pores. • Pore-scale two-phase flow simulation was done and validated with imaging results. • The developed model can be used as a tool to digitally design the inkjet printing process. • The effect of change in contact angle and ink physical properties as well as droplet impact velocity were studied. In order to control ink droplet movement into the printing-paper layer, a set of pore-scale two-phase flow simulations were performed. The high-resolution three-dimensional pore space of the paper was obtained using focused ion beam scanning electron microscopy (FIB-SEM). Solving Navier-Stokes equations yielded details about dynamic movement of a droplet into the layer. To evaluate simulation results, for the first time, confocal laser microscopy imaging technique was integrated into a FIB-SEM chamber. Doing so, high resolution imaging of the droplet penetration inside paper was conducted and computed volume of penetrated ink at final stage was compared to the imaged volume. The ink penetration and spreading extent showed a good agreement with simulation results. Therefore, the developed simulation case was further investigated to study impact of liquid contact angle, real ink properties, and droplet arrival velocity on paper surface on final print quality. A faster penetration into the paper coating was observed for smaller equilibrium contact angles; meanwhile, more radial wicking was observed. In case of velocity of impact, higher velocity caused creation of irregular shapes of the ink footprint on paper surface. In addition to that, higher velocity caused ink splash which consequently created satellite droplets and lowered the print quality. Comparing ink-like liquid (representing real ink liquid properties) with water, water moves faster than ink-like liquid into the paper. This is mainly due to the higher viscosity and lower surface tension of the ink-like liquid. [ABSTRACT FROM AUTHOR]

A chitosan-monophenol copolymer was developed as the paper coating to improve the hydrophobicity and strength. The linking type between the chitosan and laccase-catalyzed monophenol was analyzed in this work. The interaction of hydrogen bonding between the copolymer and the cellulosic fibers, as well as the corresponding influence on the hydrophobicity and strength were proposed. • A monophenol was grafted onto chitosan by the laccase. • The hydrophobicity of paper was increased after coated by chitosan copolymer. • The wet strength of coated paper was significantly enhanced. • The linkage type between chitosan and monophenol was proposed. An enzymatic method for functionalization of chitosan (CTS) with a hydrophobic monophenol compound (4-hexyloxyphenol, HP) using laccase was presented, yielding a chitosan derivative (Lac/HP-CTS) as a coating on the Kraft paper sheet. The dissolve oxygen, UV/vis, FT-IR and 1H NMR spectra were used to characterize the chemical structure of the resulting copolymer. The results showed that HP was oxidized into the semi-quinone structure, and then was bonded onto the chitosan via Schiff-base reaction and electrostatic interaction. The hydrophobicity and strength of paper were evaluated after coated by the pure chitosan or chitosan derivative. Compared with paper coated by pure chitosan, the hydrophobicity and wet strength of the coated paper via the chitosan derivative were improved significantly at the coating concentration of 0.6 g/100 mL with the coat weight of 1.53 g/m2. Meanwhile, the different enhancement behaviors in the strength (dry or wet) performance were observed, due to the greatly influenced interaction of the hydrogen bonding between the copolymer coating and the cellulose fibers by the grafted HP. Further, the hydrophobicity and strength were observed to be enhanced even at a diluted concentration of 0.1 g/100 mL and a relatively low coating weight of 0.26 g/m2 for the chitosan derivative. Taken together, this study is significant for broadening the coating application of the biomodified chitosan on the packaging papers. [ABSTRACT FROM AUTHOR]

Cellulose paper was coated with the metal-organic framework MIL-101(Cr) in a chitosan matrix and utilized for thin-film microextraction (TFME). The coated paper possesses excellent extraction efficiency for the triazine herbicides atraton, desmetryn, secbumeton, prometon, ametryn, dipropetryn, and dimethametryn. High-performance liquid chromatography-tandem mass spectrometry was applied to quantify target analytes. The effects of mass ratio of MIL-101(Cr) to chitosan, sample pH value, time of adsorption and desorption, and type and volume of desorption solvent on extraction efficiency were optimized. Under the optimal conditions, the method has limits of detection between 1.5 and 22 ng·L−1. The recoveries of triazines from spiked tap water, drinking water, lake water and river water range from 77.0 to 125.3%, with relative standard deviations of <17.4%. [ABSTRACT FROM AUTHOR]