Search

Chitosan, a renowned natural polymer for its wide application, was exploited for industry paper coating solutions. This research aimed to investigate the antimicrobial and water vapor barrier of chitosan solution-coated industry-manufactured paper. The papers were obtained from a national company in Indonesia. The commercially available chitosan with three molecular weight levels (low, medium, and high) was solubilized in sodium acetate buffer and subsequently utilized as the coating solution. The other variable studied was the chitosan concentration in the coating solution, i.e., 1.0, 1.5, and 2.0% (w/w). The antimicrobial activity study was performed by testing against Gram-positive bacteria, represented by Staphylococcus aureus, and Gram-negative bacteria, represented by Escherichia coli. The low molecular weight chitosan showed the best antimicrobial activity and water vapor barrier performance. The 1 %w low molecular weight chitosan-coated paper had shown good antimicrobial activity, against both S. aureus and E. coli, with a growth reduction of > 95 %. The most effective antimicrobial activity against S. aureus was achieved by paper coated with a 1.5% solution of low molecular weight chitosan. For low molecular weight chitosan-coated paper the most effective water vapor barrier was exhibited at 1 %w chitosan concentration. Having shown the best water vapor barrier while maintaining good antimicrobial activity, the 1.0% solution of low molecular weight chitosan was appointed as the best coating solution in this research.

Abstract In this study, zinc oxide (ZnO) nanoparticles were prepared and modified using a wet chemical method with different concentrations of Ag and Cu nanoparticles. The objective was to improve the mechanical, optical, and antibacterial properties of the coated paper by using the prepared pigments. The long-term antimicrobial effects of the coated paper were evaluated over 25 years. The successful synthesis of a hexagonal structure of ZnO nanoparticles decorated with spherical Ag and Cu nanoparticles ranging from 20 to 50 nm was confirmed using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). By increasing the concentrations of Ag and Cu from 0.01% to 1.0%, the mechanical properties of the coated paper were enhanced. The tensile strength reached a maximum of 6.77 kN/m and 7.03 kN/m, elongation increased to 1.69% and 1.70%, tensile energy absorption improved to approximately 77 and 80 J/m2, and burst strength rose to 218 and 219 kPa, respectively. The use of Ag-modified ZnO maintains the optical properties, while Cu-modified ZnO reduces brightness and whiteness without affecting opacity. The antimicrobial inhibition activity was improved with higher silver (Ag) and copper (Cu) content. The formulations containing 1% Ag/ZnO and 1%Cu/ZnO showed long-lasting antibacterial effects against gram-positive Staphylococcus aureus bacteria. Even after 25 years of aging, they maintained inhibition rates of 92.2% and 62.2%, respectively. The molecular docking and GeneMANIA analysis revealed the potential of ZnO, Ag-modified ZnO, and Cu-modified ZnO nanoparticles to disrupt the S. aureus cell wall biosynthesis pathway by targeting the MurA enzyme and associated cell wall synthesis genes.

In this study, zinc oxide (ZnO) nanoparticles were prepared and modified using a wet chemical method with different concentrations of Ag and Cu nanoparticles. The objective was to improve the mechanical, optical, and antibacterial properties of the coated paper by using the prepared pigments. The long-term antimicrobial effects of the coated paper were evaluated over 25 years. The successful synthesis of a hexagonal structure of ZnO nanoparticles decorated with spherical Ag and Cu nanoparticles ranging from 20 to 50 nm was confirmed using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). By increasing the concentrations of Ag and Cu from 0.01% to 1.0%, the mechanical properties of the coated paper were enhanced. The tensile strength reached a maximum of 6.77 kN/m and 7.03 kN/m, elongation increased to 1.69% and 1.70%, tensile energy absorption improved to approximately 77 and 80 J/m2, and burst strength rose to 218 and 219 kPa, respectively. The use of Ag-modified ZnO maintains the optical properties, while Cu-modified ZnO reduces brightness and whiteness without affecting opacity. The antimicrobial inhibition activity was improved with higher silver (Ag) and copper (Cu) content. The formulations containing 1% Ag/ZnO and 1%Cu/ZnO showed long-lasting antibacterial effects against gram-positive Staphylococcus aureus bacteria. Even after 25 years of aging, they maintained inhibition rates of 92.2% and 62.2%, respectively. The molecular docking and GeneMANIA analysis revealed the potential of ZnO, Ag-modified ZnO, and Cu-modified ZnO nanoparticles to disrupt the S. aureus cell wall biosynthesis pathway by targeting the MurA enzyme and associated cell wall synthesis genes. [ABSTRACT FROM AUTHOR]

Chitosan, a renowned natural polymer for its wide application, was exploited for industry paper coating solutions. This research aimed to investigate the antimicrobial and water vapor barrier of chitosan solution-coated industrymanufactured paper. The papers were obtained from a national company in Indonesia. The commercially available chitosan with three molecular weight levels (low, medium, and high) was solubilized in sodium acetate buffer and subsequently utilized as the coating solution. The other variable studied was the chitosan concentration in the coating solution, i.e., 1.0, 1.5, and 2.0% (w/w). The antimicrobial activity study was performed by testing against Gram-positive bacteria, represented by Staphylococcus aureus, and Gram-negative bacteria, represented by Escherichia coli. The low molecular weight chitosan showed the best antimicrobial activity and water vapor barrier performance. The 1 %w low molecular weight chitosan-coated paper had shown good antimicrobial activity, against both S. aureus and E. coli, with a growth reduction of > 95 %. The most effective antimicrobial activity against S. aureus was achieved by paper coated with a 1.5% solution of low molecular weight chitosan. For low molecular weight chitosan-coated paper the most effective water vapor barrier was exhibited at 1 %w chitosan concentration. Having shown the best water vapor barrier while maintaining good antimicrobial activity, the 1.0% solution of low molecular weight chitosan was appointed as the best coating solution in this research. [ABSTRACT FROM AUTHOR]

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]

In response to the need to employ recyclable materials for food packaging, the resurgence of paper as a primary flexible packaging material is driven by consumer trust in paper and its renewable wood fibre composition, strengthened by a well‐established recycling infrastructure. A diverse range of coated papers and coatings has become accessible in the market, specifically tailored for applications in horizontal and vertical form‐fill sealing. Within the framework of the CORNET‐TETRA project HBC.2021.0288 REPAC2, a careful selection of 16 food‐grade coated papers and/or coatings, slated for introduction to the market either presently or within the next 2 years, has been undertaken. This study focused on evaluating the processing window for superior hot tack and cooled seal performance of coated papers, in relation with the composition of paper coatings as identified using Fourier transform infrared (FTIR) measurements, and their thermal softening or melting characteristics as identified through differential scanning calorimetry (DSC). Thermal behaviour in DSC thermograms is used to categorize the commercial coated papers into distinct classes. Class I papers, mainly with acrylic‐based coatings, exhibit high hot tack strengths (0.2–0.7 N/mm) and a glass transition temperature (Tg) close to the seal initiation temperature but do not considerably gain strength with further cooling. Class II papers are thermally inert in DSC with minimal thermoplastics, leading to weak seals. In contrast, classes III and IV, including wax‐based and polyolefin‐based or polyvinylalcohol‐based (PVOH) coatings, respectively, show low initial hot tack strengths that considerably increase upon adequate cooling. Particularly, the Class IV papers with polyolefin‐based coatings have well‐performing seals. Despite having relatively low hot tack strengths after cool times of 0.1 s, below 0.3 N/mm, high strengths can be obtained after adequate cooling with outliers reaching 0.74 and 1.14 N/mm. Additionally, the influences of seal parameters on seal performance were evaluated. The study reveals that cool time, seal pressure and, to a lesser extent, seal time significantly impact hot tack strength, consistent with prior research. The critical role of jaw temperature in heat conductive sealing is affirmed, as it dictates the efficacy of other seal parameters. Seal initiation occurs at 75°C for four papers, and nine others necessitate temperatures equal to or exceeding 100°C, with one paper only displaying seal initiation at 195°C. This variation highlights the requisite for tailored temperature windows for effective sealing of these papers. As such, deeper insights into the intricate interplay between coating composition, thermal properties and seal performance are obtained in order to support advances in sustainable packaging technology. [ABSTRACT FROM AUTHOR]

The goal of this work was to improve the barrier properties of selected papers against water, grease and oil or gases (water vapor and oxygen) by covering them with biodegradable commercial coating carriers based on cellulose nanocrystals (CNCs) and polyvinyl alcohol (PVOH). The aim was also to obtain cellulose recyclable packaging materials with improved barrier characteristics. The properties of paper coatings based on CNCs and PVOH were characterized. Various paper coating techniques (flexographic printing, rotogravure printing and blade printing) were evaluated with respect to the final properties of the surface-modified paper with different starting grammages (40 g/m2, 70 g/m2, 100 g/m2). Functional properties, such as the barrier against oxygen, water vapor, water and grease; mechanical properties; and seal characterization of coated paper were examined. The results of this study demonstrated that the covering of the paper may improve the water, grease and oil barrier and that the best results were obtained for Gerstar 70 g/m2 coated with J12 coatings using the flexographic technique. [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]

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.)

Dispersion coatings are offered as alternative solutions to extrusion coating technology for paper-based packaging. In addition to providing barrier properties, waterborne dispersions may implement the processing and converting properties of coated substrates, which are of extreme interest for an effective transfer to the industry. In this work, styrene-butadiene-based aqueous dispersions were formulated considering different amounts of kaolin as pigment. The authors assessed the heat-seal ability, fold cracking resistance, and blocking tendency, comparing the results against commercial dispersion coating grades. Kaolin content dominated the sealing behavior of experimental formulations, changing the minimum heat-seal temperature from 80 °C to >140 °C for 0% and 60% kaolin solid content, respectively. On the contrary, commercial grades were mostly affected by temperature. Additionally, despite the low latex glass temperature (0 °C), experimental formulations generally showed little, if any, blocking. On the downside, increasing kaolin content eases fold cracking, showing a different magnitude according to fold direction and coat orientation yet achieving a higher moisture barrier compared to commercial grades for both folded and unfolded samples. [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]

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-TiO2 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.

In this work, the effect of using Ag-doped TiO2 nanopigments on optical, mechanical and antimicrobial properties of coated paper was explored. Furthermore, the long-term antimicrobial activity of the coated paper was examined for up to 25 years. Titanium dioxide (TiO2) nanoparticles have been synthesized and doped with different percentages of Ag nanoparticles (Ag NPs) using a simple wet chemical approach. The Ag@TiO2 modified nanopigments were in the form of nanorods with an average size of about 20 nm as observed from TEM images. Increasing Ag content from 0.01 to 1.0% showed an increase in the mechanical properties of coated paper in terms of tensile, stretching, tensile energy absorption and burst while preserving the optical properties. Moreover, the antimicrobial inhibition activity increased with increasing the Ag content. The 1% Ag@TiO2 showed a long-lasting antimicrobial effect against Staphylococcus aureus (S. aureus) Gram-positive bacteria even after 25 years of ageing (93.4% inhibition). Investigation of reactive oxygen species (ROS) generation and reaction mechanism of antimicrobial activity over Ag/TiO2 under visible light is proposed. These results suggest that Ag/TiO2 NPs can be potentially used as a disinfection coating for paper and improving its mechanical properties. [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]

Abstract 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.

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]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology 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.)

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.

Half-tone mottle is due to uneven ink transfer and ink penetration, which generates an inhomogeneous image to the human eye, thereby affecting the saleability of the product. Design of Experiments (DOE) was done with gravure process parameters such as line screen, ink viscosity, press speed, ESA (Electrostatic Assist) voltage and the air gap at varying levels to evaluate the effect of these process parameters on half-tone mottle. The Stochastic Frequency Distribution Analysis (SFDA) algorithm was used to measure surface properties of paper and half-tone mottle. The experimental data were analysed through ANOVA, main and interaction plot. The results revealed a reduction in mean halftone mottle by 90.48% and 91.25% for 50 GSM and 65 GSM C1S paper respectively. The regression models were developed and validated by conducting additional runs. The results hence obtained shall help to optimize ink transfer and identify the key process variables minimizing half-tone mottle; thereby enhancing the print quality.

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 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 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]

1‐Methylcyclopropene (1‐MCP) has been shown to be a suitable inhibitor of ethylene production in fruit and vegetables during preservation and distribution. In this study, a 1‐MCP controlled‐release system on coated paper was produced using shellac as the coating material. The effect of humidity and temperature on the release of 1‐MCP from the coated paper was investigated using a dynamic sorption system (DVS) with stepwise humidity changes (initial 20% relative humidity (RH) for 2 h, then increased to 40%, 50%, 60%, and 80% RH for 2 h, respectively). The release rate kinetic data were simulated using an Avrami equation with a mechanism release number n of 1.26. The results showed that the dynamic release of 1‐MCP from the coated paper was mainly affected by humidity, for which the release rate constant could be correlated with moisture concentration in humid air. The highest humidity condition (80% RH) resulted in the highest apparent activation energy of 46.8 kJ/mol. The effect of 1‐MCP coated paper on apple storage was evaluated by measuring the ethylene production rate, flesh firmness, and titratable acidity (TA) of apple. Ethylene production rates of apple were significantly affected with 1‐MCP coated paper. The values were 0.22 nL/g FW/h at 50 mg of 1‐MCP powder and 44.7 nL/g FW/h at 0 mg of 1‐MCP powder after 15 days at 4°C and 15 days at 20°C. The other properties of apple such as flesh firmness and TA also indicated that 1‐MCP coated paper could delay fruit softening during storage time. Based on these results, the release of 1‐MCP could be controlled by coating paper with shellac solution and promising to produce functional packaging for fruit. [ABSTRACT FROM AUTHOR]

Coated paper is an example of a multi-layer porous medium, involving a coating layer along the two surfaces of the paper and a fibrous layer in the interior of the paper. The interface between these two media needs to be characterized in order to develop relevant modeling tools. After careful cutting of the paper, a cross section was imaged using focused ion beam scanning electron microscopy. The resulting image was analyzed to characterize the coating layer and its transition to the fibrous layer. Such image analysis showed that the coating layer thickness is highly variable, with a significant fraction of it being thinner than a minimum thickness required to keep ink from invading into the fibrous layer. The overall structure of the coating and fibrous layers observed in this analysis provide insights into how the system should be modeled, with the resulting conclusion pointing to a specific kind of multi-scale modeling approach. [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]

Mechanical properties of paper coating layers are very important in converting and printing operations. Kaolin is commonly used in paper coating as cheap pigment in addition to its superior properties. In this study, a new approach for improving coated paper mechanical properties using doped kaolin with ammonium molybdate was presented. Kaolin and modified kaolin were characterized using several analyses tools (e.g., XRD, SEM, and EDX), and then they were applied in paper coating mixture. The results revealed that the dopant was found in the kaolin as MoOx; this oxide form with its needle shapes led to change in the kaolin crystals, and its presence in high concentrations led to exfoliation of kaolin. Also, at high concentration it was found that MoOx reacted with γ-alumina that is found in kaolin after its heating at 300°C to form aluminum molybdate. It can be observed that modified kaolin increased the coated paper porosity and consequently the opacity; also bulk and thickness were increased. Significant improvement in coated paper tensile strength, bursting strength, tensile energy absorption, and bending stiffness was also noticed. Thermal study also showed that increasing the concentration of ammonium molybdate increased the heat stability of the coated paper. [ABSTRACT FROM AUTHOR]