Coated Paper Surface Research Articles

Preparation of high‐barrier performance paper‐based materials from biomass‐based silicone‐modified acrylic polymer emulsion

AbstractHigh‐barrier performance, especially under extreme working conditions, is the key to replacing other types of packaging materials with paper‐based materials. In this paper, two biomass‐based polymers, sodium alginate (SA), and chitosan, were used to form a barrier coating with silicone emulsions to prepare a high‐performance paper‐based barrier material. By double coating, the water and oilproof functions were superimposed. The two prepared coated papers were characterized by infrared spectroscopy analysis, contact angle test, and scanning electron microscopy analysis, while their water resistance, oil resistance, thermal oil resistance, and thermal stability were tested. The water and oil repellency were achieved by double coating. The Cobb value of the chitosan‐silicone emulsion‐coated paper reached 5.3 g/m2, with a Kit grade of Level 12, and could block the penetration of castor oil at 80°C within 24 h. The Cobb value of the sodium alginate‐silicone emulsion‐coated paper was 41.6 g/m2, much higher than that of the uncoated paper, with a Kit grade of up to Level 10, which could slow down the rate of castor oil penetration at 80°C within 24 h. The test results showed that there was no chemical reaction between the paper‐based coatings, and the coated paper surface had good film formation, while the double coating method increased the thermal decomposition temperature of the overall barrier coating, effectively improving the thermal stability of the coating and achieving high‐barrier performance at lower cost and under extreme working conditions.Highlights Water and oil resistance under extreme operating conditions. High‐performance paper‐based barrier materials. Dual‐layer coating method for water and oil repellency. High‐barrier performance at lower cost. Excellent hot oil resistance and thermal stability.

Biodegradable active coating from chitosan/astaxanthin crosslinked with genipin to improve water resistance, moisture and oxygen barrier and mechanical properties of Kraft paper

An active chitosan-based coating with an addition of a natural antioxidant and a natural crosslinker has been applied to improve the performance of Kraft paper. Coatings, including chitosan (CS), CS crosslinked with 1.5 % genipin (CS-1.5G), CS containing 1 % astaxanthin (CSA) and CSA crosslinked with 1 % genipin (CSA-1G) were coated on Kraft paper. Uncoated and coated papers were then evaluated for water content (WC), water vapor permeability (WVP), contact angle, oxygen permeability (OP), tensile strength (TS), bursting strength and elongation at break (EAB). Results indicated that the coating improved the properties of Kraft paper. When compared with CS-coated paper, WC and WVP of CSA-1G-coated paper decreased significantly by 40 % and 24 %, respectively. The lowest OP was also observed in CSA-1G-coated paper. CSA- and CSA-1G-coated paper had contact angle values >100°, indicating hydrophobic nature of coated paper surface. All coatings largely improved TS of the paper (by 182–224 %) whereas CS-1.5G and CSA-1G significantly improved the bursting strength of the paper. The developed genipin-crosslinked chitosan-based coating enriched with astaxanthin can improve the functional properties of Kraft paper and thus will facilitate the usage of the paper for food packaging applications.

Transfer-Printed Environmental-Friendly Anisotropic Filter with Laser-Controlled Micropores for Efficient Oil/Water Separation

Water is indispensable for sustaining life on Earth. Oil–water mixtures/or emulsions from industrial waste and other sources are a serious environmental concern for both human beings and aquatic life. Specially treated meshes and textiles with opposing wettability for oil–water separation have been widely reported as a solution to this challenge. Nonetheless, such membranes are hindered by certain drawbacks, including high manufacturing costs, usage of harmful chemicals, and lack of diverse applicability. Here, we report a facile method to fabricate Janus oil–water separation membrane with a controllable pore structure that has a unique directional flux rate. The superhydrophobic (SHB) layer of the membrane is formed by transfer-printing (TP) carbon soot particles onto a polydimethylsiloxane (PDMS)-coated paper surface. Meanwhile, a spin-coated thin layer of chitosan on the other side of the film served as a hydrophilic (SHL) and underwater oleophobic face. A pulsed laser beam is used to produce micropores with conical structures. The separation ability of the membrane for both light oil–water and heavy oil–water mixtures is thoroughly investigated. Moreover, the significance of the pore shape and the size is also elucidated. The flexible Janus membrane showed high thermal stability and ideal (i.e., 99.8%) separation efficiency. The membrane can be produced over a 151 cm2 size range. Besides having flexibility and superior performance, the fabricated membrane is environmentally friendly and economically viable. This work establishes a scalable basis for efficient and low-cost oil/water membranes from non-porous substrates.

Achieving reversible superhydrophobic-superhydrophilic switching of lignocellulosic paper surface with modified Nano-TiO2 coating

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.

Cellulose nanofiber assisted dispersion of hydrophobic SiO2 nanoparticles in water and its superhydrophobic coating

It is challenging to build a superhydrophobic coating with aqueous dispersions since hydrophobic substances are usually dispersed in pure organic or water/organic mixed solvents. In this study, hydrophobic SiO2 nanoparticles were dispersed in water assisted with cellulose nanofiber (CNF) and the superhydrophobic surface was manufactured by coating a waterborne dispersion composed of CNF, hydrophobic SiO2 nanoparticles and methyltrimethoxysilane (MTMS). It was found that the dispersion of SiO2 in water can be improved by CNF. Meanwhile, the coated paper surface retained its hydrophobicity after 10 abrasion cycles due to the adhesion of the coating surface promoted by MTMS. When SiO2 content over 0.25 wt%, the coated paper surface displayed a superhydrophobic property, and the moisture absorption decreased to 31–34%. The contact angle of the coating surface was 162°, the contact angle hysteresis was 1.96° and the rolling contact angle was 1.33° when SiO2 content was 1 wt%.

Residual-Based Surface Segmentation for Monitoring Topographic Variations

Monitoring topographic variations in the engineered surface is crucial for quality engineers since the change in the surface finish is closely related to the performance of products. However, several challenging issues such as the existence of spatial autocorrelation within the surface, and changes of topographic features such as position and shape of peaks and valleys across defect-free surfaces make it difficult to monitor variations in the surface. In addition, existing monitoring approaches fail to detect local changes in the surface. In this article, we present a new approach for monitoring topographic variations in surfaces. We develop a residual-based separation deviation (RBSD) model to effectively identify local surface changes. Residuals are obtained through the fit surface prediction model, which characterizes the generic behavior of defect-free surfaces, and binarized by the RBSD model to distinguish the defective region where residuals are autocorrelated. A spatial randomness-based monitoring statistic is introduced to evaluate binary patterns in order to detect surface anomalies. Numerical simulation and a case study of the coated paper surface monitoring are provided to demonstrate the effectiveness of the proposed approach. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —An increasing number of optical measuring instruments provide quality engineers with surface topographic data of the product, and enable precise and accurate inspection of surface variations during the manufacturing process. However, spatial and arbitrary geometric features on topographic data often make monitoring the surface changes a challenging task. This article proposes a new monitoring approach for detecting topographic variations in the surface. We mathematically characterize the generic behavior of the surface under the normal process, and present a surface segmentation model to detect local variations in the surface. In practice, our approach is applicable to real-life paper surface variations monitoring. The proposed approach is expected to provide a new idea to practitioners who work on surface topography inspection in various fields as well as the pulp industry.

The effect of zeolite on inkjet coated paper surface properties and deinking

Abstract Coatings are generally applied for opacity, smoothness and gloss on the paper surface. Pigments such as CaCO3, Kaolin-Clay and Zeolite are used, and natural or synthetic binders are used. In this study, coatings using the CaCO3, Kaolin-Clay and Zeolite pigments on 80 gr/m2 high grade papers were made. PVOH was used as binder. Following coating, papers were processed through supercalendering and printed with inkjet printer. Using INGEDE method 11p. recycling process printed papers were deinked. The optical properties of the recycled papers obtained after the deinking treatment, were compared with the unprinted papers. At the end of the study, the effect of coating on paper surface and the recycling performances of the inkjet printed papers were revealed. It was determined that the papers in which zeolite was used as a pigment were better, in terms of both surface properties and recycling performance when surface properties and recycling performance of coated papers were examined. When all the results were compared, it was found that the performances of coatings for which zeolite was used were much better than coatings such as CaCO3 and Kaolin-Clay, both in terms of surface coating properties such as opacity, roughness and gloss and recycling results such as brightness.

Nanocrystalline Cellulose and Polyvinyl Alcohol Coating Application to Cardboard Packaging Papers and Investigation of the Effects on Paper Properties

In the packaging sector of the printing industry, different coating applications are tried and investigated in order to increase the surface appearance and performance characteristics of paper and cardboard. The printability, water and ink absorption capacity, frictional resistance, light sensitivity of the visual graphical design that are going to be printed on the packaging papers are some of them. In this study, different types of cardboards that are used as a packaging material were chosen and coated with nanocrystalline cellulose (NCC)/PVA at different rates (%). In order to determine effective and economical usage conditions, the coating solutions, at three different concentrations as 3 wt.%, 5 wt. %, 7 wt.%, were prepared. The coating was applied on the test papers, which were at the same weights (350 g/m2) and had different surface properties as matte glossy, bright glossy, American Bristol. NCC/PVA existence on the coated paper surface was confirmed with Fourier Transform Infrared Spectroscopy (ATR-FTIR). The impact of the coating, which was prepared at different concentrations, on the packaging materials was studied with respect to thickness, stiffness, water absorbability, contact angle and surface tension.

Characterization of flame coated nanoparticle surfaces with antibacterial properties and the heat-induced embedding in thermoplastic-coated paper

Silver nanoparticles deposited on surfaces can provide an antibacterial effect with potential uses in, for example, healthcare settings. However, release of nanoparticles and their potential exposure to the environment is of concern. The current work demonstrates a continuous synthesis that simultaneously deposits silver nanoparticles onto plastic coated paper surface by utilizing the liquid flame spray (LFS) aerosol process. Heat from LFS is used to soften the thermoplastic paper surface, which enables partial and full embedding of the nanoparticles, thereby improving adhesion. The embedding is confirmed with atomic force and scanning electron microscopy, and the deposited silver amounts are quantified with X-ray photoelectron spectroscopy. The results suggest that embedding was more effective in PE-coated paper samples due to the lower glass transition temperature when compared to PET-coated paper samples. The antibacterial properties of the surfaces against E. coli and S. aureus were maintained and confirmed with a previously developed ‘Touch-Test Method’. The LFS process has the potential to be used for large-scale manufacturing of antibacterial surfaces with improved nanoparticle adhesion on appropriately chosen thermoplastic surfaces.

Application of Industrially Produced Chitosan in the Surface Treatment of Fibre-Based Material: Effect of Drying Method and Number of Coating Layers on Mechanical and Barrier Properties.

Chitosan is a versatile biopolymer with many interesting functionalities. Its effects on the barrier and mechanical properties of single- or double-coated fibre-based packaging papers in dependence on the applied drying regime were successfully tested. Our investigations revealed chitosan to be a highly robust biopolymer, since the different drying regimes did not alter its contribution to the development of strength and barrier properties of the coated packaging papers. These properties showed a stronger influence of the applied coat weights than of the different drying regimes. The effect of chitosan coatings were quantified by measuring tensile strength (TS), burst strength (BS) and tensile energy absorption (TEA). These revealed that TS, BS and TEA of the coated papers increased significantly. Moreover, the chitosan-coated papers were less permeable against water vapor and air. High grease resistance was observed for double-coated papers, irrespective of the drying regimes. The coated paper surface showed a more hydrophilic character, resulting in lower contact angles and higher water absorption properties. In this study, industrially produced chitosan has been proven to be a renewable, robust biopolymer that can be utilized as an additive to increase strength and the barrier properties of fibre-based materials.

Characterizing coated paper surface for modeling apparent dot area of halftone prints.

A new model is proposed for predicting the apparent dot area of simulated halftone prints on coated paper surface without requiring printing. It is based on Hotelling's multivariate T(2) statistic which is shown to provide a measure of lateral light scattering. The T(2) statistic is computed from colorimetric coordinates obtained from of a knife shadow image response on the paper surface. The proposed method offers superior prediction of halftone dot area compared to current light scattering models. A method for characterising peaks on the coated paper surface is introduced in this work. The effect of the paper coating layer thickness and the surface peak height on lateral light scattering and printed dot size are shown.

Study on the Effect of Calender on Coating surface structure and Printability of Coated Paper

The structure of the coating layer has a strong influence on the optical and physical properties of paper as well as on the print quality. Ink is transferred and sets onto the paper surface in the printing process, which affect printing quality and usage of ink. The objective of this experiment was to investigate the influence of calender on coating surface structure and Printability. The surface structure was explored in the method of numerical and visual analysis using mercury porosimetry measurement and scanning electron microscopy (SEM). The findings indicated that the calender treatment affected the pore size, depth and distribution of the coated paper surface. It could be concluded that Calender could increase the smoothness, gloss and paper surface efficiency of coated paper, which resulted in lower amount of ink usage, lower amount of ink absorption and higher print density.

Investigation into Coating Surface Free Energy and Microstructure of Coated Paper Related to Pigment

The physical structure of coating layer have an important influence on transferring and setting of the printing ink. In this study, the effect of pigment on surface microstructure and surface free energy was investigated. The findings indicated that the pigment affected the pore size, depth and distribution of the coated paper surface. Kaolin pigment compared with calcium carbonate pigment was good to improve the paper surface smoothness. Surface free energy of kaolin pigment coating was higher than calcium carbonate pigment coating, which showed that surface wettability of coating with kaolin pigment was better than calcium carbonate pigment.

Research on the Coating Surface Microstructure of Coated Paper Related to Binder Migration

The surface topography and properties of coating layer have an important influence on penetration and distribution of the print ink. In this research, the main objective was to investigate the effect of binder migration on the coating surface microstructure. The surface microstructure was explored in the method of numerical and visual analysis using mercury porosimetry measurement, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The findings indicated that the binder migration on the coating surface affected the pore size, depth and distribution of the coated paper surface. The little binder migration in the consolidation phase of coating color made a contribution to the forming of the coating layer, which made the coating surface more smother to printing performance.

ToF-SIMS Analysis of UV-Switchable TiO2-Nanoparticle-Coated Paper Surface

The chemical composition of a TiO2 nanoparticle coated paper surface was analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study the interconnection between wettability and surface chemistry on the nanoscale. In this work, a superhydrophobic TiO2 surface rich in carboxyl-terminated molecules was created by a liquid flame spray process. The TiO2 nanoparticle coated paper surface can be converted by photocatalytic oxidation into a highly hydrophilic one. Interestingly, the hydrophilic surface can be converted back into a superhydrophobic surface by heat treatment. The results showed that both ultraviolet A (UVA) and oven treatment induce changes in the surface chemistry within a few nanometers of the paper surface. These findings are consistent with those from our previously reported X-ray photoelectron spectroscopy (XPS) analysis, but the ToF-SIMS analysis yields more accurate insight into the surface chemistry.

A Study of Coating Surface Microstructure and Characteristics of Coated Paper Related to Binder

The surface topography and properties of coating layer have an important influence on penetration and distribution of the print ink. In this research, the main objective was to investigate the effect of binder on the coating surface topography and characteristics. The surface microstructure was explored in the method of numerical and visual analysis using mercury porosimetry measurment and atomic force microscopy (AFM). The findings indicated that the binder content on the coating surface affected the pore size, depth and distribution of the coated paper surface. The conclusions were drawn that more amount of binder on the coating surface could contribute to improve the coating surface topography and the formation of even pore size and distribution, which was good to the paper surface characteristics and resulted in low roughness, high paper gloss, low ink absorption and high paper surface efficiency.

Study on Coating Surface Topography and Properties of Coated Paper Related to Pigment

The physical structure and chemical properties of coating layer have an important influence on transferring and setting of the printing ink. In this study, the effect of pigment on coating layer structure and surface properties was investigated. The surface topography was explored using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The findings indicated that the pigment affected the pore size, depth and distribution of the coated paper surface. The conclusions were drawn that coating could improve coating surface topography and calcium carbonate pigment compared with kaolin pigment was not good to the paper surface properties, which resulted in high roughness, low paper gloss, high ink absorption and low paper surface efficiency.

Investigation into the Coating Surface Topography and Properties of Paper Related to Drying Condition

The physical structure and chemical properties of coating layer have an important influence on transferring and setting of the printing ink. The typical objective of coating is to improve the appearance and printing properties of paper. In this study, the effect of drying condition on coating layer structure, surface properties, and print quality was investigated. The relationship between surface topography and drying condition was explored using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The conclusions were drawn that high and low drying temperature were not good to the paper properties, which resulted in high roughness, low paper gloss, high ink absorption, low print gloss and paper surface efficiency. The findings indicated that the coating drying temperature affected the pore size, depth and distribution of the coated paper surface. Moderate temperature was benefit to pigment particles and binder arranging orderly, which made the coating surface had high smoothness, gloss, paper surface efficiency, and modest ink absorption.

New advances in the 3D characterization of mineral coating layers on paper

The surface characteristics of a large set of commercial lightweight coated paper grades are explored. The quantification of the 3D structure is revealed by atomic force microscopy, laser profilometry and X-ray microtomography. This comprehensive study demonstrates the suitability of different and modern methods for assessing critical coating layer properties, thus identifying the right tools for specific structural analyses. Based on the assessment of the top and bottom surfaces of 25 commercial lightweight coated samples, three main conclusions can be drawn: (1) the facet orientation polar angle is a function of roughness, (2) skewness did not describe the surface details affecting the gloss of the commercial lightweight coated samples assessed in this study and (3) surface roughness at wavelengths below approximately 1.0 microm does not affect the paper gloss significantly. This is important knowledge for the understanding of lightweight coated paper surface structure and its properties.

Surface Characteristics of Coated Paper Improved by Plastic Pigments and Synthetic Thickeners

Synthetic thickeners, either polyacrylate or associative types, have been extensively used in paper coating. However, systematic research on the effect of these thickeners on coated paper surface structure in the presence of plastic pigment is still inadequate. In the current work, we compared and contrasted several commercial plastic pigments (PP), focusing on two hollow sphere and two solid bead plastic pigments having various particle sizes. Two types of polymeric thickeners were also selected, and their influence on the roughness and surface structure of coated paper were investigated. The results confirmed that the incorporation of plastic pigment in the clay coating mixtures resulted in a substantial decrease in the roughness of coated paper. The effect was particularly pronounced with hollow sphere plastic pigments. The addition of polymeric thickeners further reduced the roughness of the coated paper, for both clay/PP and ground calcium carbonate/PP systems. In coating mixtures based on clay, it was found that hydrophobically modified alkali swellable emulsion (HASE) thickener has a stronger effect on reducing the roughness of clay-based coated paper than polyacrylate thickener. The trend is opposite in the case of a ground calcium carbonate (GCC) coating system.