Paperboard Surface Research Articles

Lignocellulose nanofiber and starch for surface application on recycled linerboard

In a paper production line, starch is widely used for surface treatment and strengthening of linerboard at a size press. Also, the application of lignocellulose nanofibers (LCNFs) is growing because of its relatively low production energy demand, cost, and less hydrophilic nature in comparison to lignin-free nanofibers. Therefore, the addition of LCNFs to starch for paper surface treatment to reinforce the starch film and improve certain physical and mechanical properties of recycled linerboard was investigated in this work. Various LCNF/starch ratios were homogenized and then applied on the paperboard surface. The results revealed that a low mixing ratio of LCNF (5%) with starch improved the tensile index of the recycled paperboard, and at 50% LCNF content in the surface-treating material, film forming on the linerboard was observed in field emission-scanning electron microscopy images. In the case of 95% LCNF addition to starch, bending stiffness was significantly increased. Additionally, the viscosity of the sizing suspension was studied as a crucial parameter in the process and was found to increase significantly following the addition of LCNF.

A new and easy-to-implement green packaging option with recycled paperboard and PBAT film

A commercial recycled paperboard was double coated with poly (butylene adipate-co-terephthalate) (PBAT) films by using hot pressing aiming the production of a laminated material compatible with food packaging. The proposed new approach allowed to smooth the paperboard surface and to obtain a material with low oxygen permeability, low wettability, and excellent resistance to grease (kit value of 12). The observations by scanning electron microscopy (SEM) showed a homogeneous surface with a high degree of coverage, suggesting good compatibility of the PBAT with the cellulose fibers. Some of the mechanical properties of the PBAT-coated paperboard were also greatly improved, such as ply-bonding, bending resistance and bursting strength, which are important for packaging applications. Remarkably, it was possible to firmly bond two pieces of paperboard coated with PBAT by simply hot-pressing at an appropriate temperature. This method created a reinforced coated paperboard that showed high potential to be used in the production of laminated food packaging with different structures without the need of adhesives.

Bio‐based multilayer paperboard for sustainable packaging application

AbstractBio‐based packaging materials are an emerging environment‐friendly alternative to conventional plastic food packaging materials, at least for some applications. The innovation of this work was to develop a sustainable cellulosic packaging material based on chitosan/palmitic acid/activated carbon coating with potential applications for single‐use food packaging. The study developed a multilayer paperboard (MPB), evaluating the effects of a paperboard surface coating by chitosan (2.0% w/w), palmitic acid (1.8% w/w), and activated carbon (1.2% w/w) applied in three coating layers. The water vapor transmission rate (WVTR) of coated paperboard was reduced compared to uncoated paperboard, associated with the coating suspension filling of the pores of the cellulosic matrix, the palmitic acid hydrophobic characteristic, and the nonpolar nature of activated carbon (acted by repelling the vapor molecules of water). A grease resistance of Kit solution 11 of MPB was observed. The stiffness and elongation capacity increased, indicating the rigidity and flexibility of the MPB. The deposition of palmitic acid and activated carbon influenced the roughness increase. The biodegradability in the soil after 188 days of MPB was 55.01%, and the control (uncoated paperboard) was 69.38%. The coating did not impact the degradation behavior of cellulose.

Sustainable Coating Paperboard Packaging Material Based on Chitosan, Palmitic Acid, and Activated Carbon: Water Vapor and Fat Barrier Performance.

Synthetic polymer coatings impact the biodegradable behavior of cellulosic packaging material. The environmental consequences of food packaging disposal have increased consumer concern. The present study aimed to use natural polymer coatings incorporating palmitic acid and activated carbon applied to paperboard surfaces as a sustainable alternative to improve cellulosic packaging material's moisture and fat barrier properties, minimizing the environmental impact. The coating formulation was defined using a Factorial Experimental Design with independent variables: chitosan, palmitic acid, activated carbon concentrations, and the number of coating layers. The highest concentration of chitosan (2.0% w/w) filled the pores of the cellulosic paperboard network, supporting the compounds incorporated into the filmogenic matrix and improving the fat resistance. The water vapor permeability of the coated paperboard material (range: 101 ± 43 to 221 ± 13 g·d-1·m-2) was influenced by the hydrophobicity effect of palmitic acid, the non-polar characteristic of activated carbon, and the number of applied layers. The coating formulation selected was a chitosan concentration of 2.0% (w/w), a palmitic acid concentration of 1.8% (w/w), an activated carbon concentration of 1.2% (w/w), and an application of three layers. The coating provides the potential for a paperboard surface application, improving the cellulosic packaging material's fat and moisture barrier properties and maintaining biodegradability and recyclability.

EFFECT OF PAPERBOARD SURFACE MODIFICATIONS ON ELECTRICAL CONDUCTIVITY OF PRINTED UHF RFID ANTENNAS

The effect of surface roughness and water contact angle of commercial paperboard before and after surface modification by calendering, coating and calendering and plasma treatment on the functionality of UHF RFID antennas printed with thermal transfer aluminum ribbon was evaluated. A hydrophilic surface was created by coating or plasma treatment, which improved the wettability of the paperboard surface, the spreading of the thermoplastic tie layer and theadhesion of the conductive aluminum layer. Anew paper product was created with permanent surface wettability by coating, without theneed for plasmatreatment before printing. Theplasma treatment provided time-limited wettability, needed only during printing, and made it possible to restore the original hydrophobic surface of thepaperboard. In addition to themeaning of these surface modifications, the importance and need to reduce the surface roughness was confirmed, as the higher surface roughness of the paperboard limited the effect of the plasma treatment in terms of its printability and the functionality of the printed aluminum antenna. The printability of the paperboard and the functionality of the printed antennas were evaluated using electrical conductivity. The electrical conductivities of the dipole and inductor loop of the UHF RFID antennas printed on modified paperboards varied depending on theantenna design.

Improvement of Package Properties with Formed Functional Surface Features

Paperboard package properties can be improved by embossing functional features on package surfaces. Embossing is used in package manufacturing as an additional tool to improve the appearance of the packages. It can also be used to increase product safety by improving functionality and identifiability of packages. Creation of features directly on the base material without implementing additional components improves the sustainability level of package applications. To evaluate functionality of features, such as protective surface patterns, in the applicable practice, the following steps need to be gone through; design phase, tool manufacturing phase, pattern production phase and analysis phase. Bespoken toolsets were designed and manufactured to form a protective frame around commercial radio-frequency identification tag (RFID). The essential process parameters in the embossing experiments were the pressing force and the plate temperature which were optimized in preliminary tests. Methods for evaluating the performance of created embossed patterns were wear testing of package surfaces, topography measurement with a 3D profilometer and SEM-imaging for more detailed analysis. The results show that embossing is a suitable manufacturing method for creating targeted functional features on paperboard surfaces. With the formed surface features, the functionality of the packages was improved by protecting the identification labels.

Chitosan active coating on paperboard surface forming an anti‐insect grain‐based food packaging

In the food chain, the packaging is an intermediary product between the food industry and consumers. It represents a critical step in food quality preservation and the ultimate protection against insect pests. Insects may infest grain‐based food products during their packed life. Active packaging systems involve intentional interaction with food or its surroundings, and a few studies have been focused on anti‐insect packaging materials for food. The aim of this work was to develop a sustainable and active packaging material based on chitosan coating on paperboard surface incorporating lemongrass essential oil with potential action against weevil infestation in cereal‐based food packed products. The innovation is the eco‐friendly packaging development by applying natural and biodegradable compounds to prevent stored product insect infestation in the grain‐based product. The effects of chitosan and lemongrass essential oil (LG) concentrations and the number of coating layers were studied. The active packaging material was anti‐insect efficient against adult weevils in wheat grain and pasta package. The active coating reduced the air and water vapour transmission rate, and water absorption capacity improved the fat barrier while maintaining a microbial impermeability. The proposed active packaging material presented a potential application to extend the shelf life of grain‐based food products against weevil infestation.

Printability of paper and paperboard surface treatment with gum rosin and derivatives

PurposeThis study aims to provide control of liquids, especially against water-based ink on the paper and paperboard surface with natural substances, in also practical and greenway.Design/methodology/approachThe paper surface was treated with natural rosin and its derivatives to obtain a hydrophobic effect and to improve printing properties. The oleoresin samples collected from Pinus nigra Arnold and Pinus pinaster Aiton trees in the controlled area and turpentine content removed was by hydrodistillation. The gum rosin (GR), fortified 10% with maleic anhydride (MGR) and esterified with 10% pentaerythritol (PMGR) samples solved in a simply alcohol and sprayed the base paper surface directly with a spray gun. Base paper samples were paperboard, bleached paper and test liner paper. Then, flexo printing was applied and printability properties were measured.FindingsThe treatment weights of these paper samples were 1.8 ± 0.5, 1.3 ± 0.5 and 0.7 ± 0.2 g/m2, respectively, compared to the base paper. Greater Cobb60 results were obtained from modified rosin samples than unmodified gum rosin-sized paperboards and the PMGR surface treatment reduces Cobb60 values by 20% and MGR treatment reduces 15% comparing to the base sheet. Then, the printing procedure was applied to the surface of the treated materials using a flexo printing system. As a result of the treatment better print density, chroma and print lightness value consumed a less hydrophobic agent and controlling water-based flexo ink on the base paper surface.Originality/valueThe unique aspect of this work was improving the hydrophobicity of the paper surfaces was achieved by spraying with natural rosin and derivatives.

Water resistance improvement of paperboard by coating formulations based on nanoscale pigments

This research assessed how type, particle size, and concentration of pigment in coating formulations influenced water and water vapor barriers of paperboard packaging. Calcium carbonate (CaCO3) and kaolin of micro- and nanosize of 1 and 0.05 µm, respectively, were added to 3% (w/v) gelatinized cassava starch to prepare coating formulations with different pigment concentrations of 5, 15, and 25% (w/v). These were applied on paperboard surfaces using the rod coating technique. Results showed that water resistance of paperboard, evaluated by contact angle (CA) and water absorptiveness (Cobb) were strongly influenced by pigment type (chemistry), particle size and shape, and pigment concentration (coating layer thickness). A hydrophobic surface (CA > 100) was obtained only for the nano-CaCO3 formulation with 25% (w/v) by combined effects of the nanosize scale, the spherical shape, and the hydrophobic surface of CaCO3 particulates. Kaolin nanoparticle coatings produced hydrophilic surfaces (CA ~ 90) with high water absorptiveness, while high concentrations of kaolin microparticle coating slightly improved water and water vapor barriers by compact arrangement of flattened particles. Mechanical strength properties of the paperboard were not significantly affected by coatings, but surface cracking was observed for large particle size or at high pigment concentration due to the increase in pigment/starch ratio.

Surface Fracture Prevention in Paperboard Press Forming with Advanced Force Control

Press forming is a three-dimensional forming process used for industrial converting of large quantities of fibre-based composite materials such as barrier coated paperboard. The technology enables the production of plate and tray packages of such high quality that it is possible to lid seal them to create a gas-tight package. The method is primarily based on the controlled folding and compression of materials using high forming forces and elevated tool temperatures.The corner of the container is folded utilizing creases and a certain amount of force is needed to achieve the desired result. Sliding of the package blank is restrained with blank holding force which defines the overall forming force. The magnitude of blank holding force is determined by the shape and dimensions of the package and the properties of the material to be moulded.In some cases, the force optimized to produce high-quality packages will cause fractures, which are only on the surface layer of the paperboard, at corners of the tray. The packaging is still fully functional, but the visual disadvantage makes it look defective. The phenomenon is accentuated in converting of printed paperboard, where the potentially brittle surface layer breaks more easily and the colour difference makes the fractures eye-catching.This study investigated how by adjusting the blank holding force, paperboard surface layer breakage can be prevented during processing. Various ramps were programmed to control the forming cycle, which changed the magnitude of the force during the pressing stroke. The results show that there is no need to compromise the quality of the package as long as the average magnitude of the blank holding force is maintained. If the strength properties of the material to be formed are not sufficient to apply a constant blank holding force, by reducing the force slightly at certain points in the process cycle, material damage can be reduced or prevented completely.

Laser-pyrolyzed electrochemical paper-based analytical sensor for sulphite analysis

A CO2 laser can be used to pyrolyze the surface of common paperboard to produce a conductive carbon material for subsequent use as an electrode for general electrochemical measurements. In this work, a laser-pyrolyzed electrochemical paper-based analytical device (LP-ePAD) of this type was combined with a gas-diffusion microextraction (GDME) unit for the square-wave voltammetric analysis of sulphites in commercial beverages. The fabricated LP-ePAD had a resistivity at room temperature of 11 ± 4 Ω per square electrical sheet (measured with a four-point probe system). The developed methodology showed a limit of detection of 1 mg L−1 for sulphite analysis, with good repeatability and reproducibility (coefficient of variation below 7%), as well having as the desirable qualities of portability and low price.

The influence of pigment proportions and calendering of coated paperboards on dot gain

Dot gain is called Tone Value Increase (TVI). Low dot gain and rounder dot shape are important properties to obtain a good print. Dot gain is a measure of how much extra weight a given percent dot or tone has gained on the final printed substrate by comparison to the actual dot area on a press plate. Dot gain value depends on many factors. The interactions of paper, ink and press conditions are important determinates for a good print. In addition, the pigment coating process and calendering conditions have a significant effect on the printability of paperboards. Pigment coating formulations including mineral pigments, binders and additives improve the gloss, brightness, opacity and smoothness of the paperboards. As a result, print quality of paperboards increase. A uniform paperboard surface is needed to obtain a high quality surface smoothness after the coating process. High surface smoothness improves the uniformity of the dot shape and size. Pigment coating formulation parameters; pigment selection, binder selection and binder level influence print quality. The aims of this study - pigment selection and ratio - are to determine the effect on dot gain in lithography printing. To this aim, base paperboards were coated using five pigment coating formulations which included different combinations of kaolin, calcium carbonate and titanium dioxide pigment with a styrene\n-butyl acrylate copolymer binder using a bar application. After coating, the samples were air-dried overnight under TAPPI conditions. Then, half of the coated-paperboards were calendered. Tone scales from 1 to 100 % were offset printed using black ink on the uncalendered and calenderedcoated paperboards. Then, from the printed tone scale, the tone area values were measured with the Gretagmacbeth Spectrolino spectrophotometer. These values showed that pigment coating improved the surface optical and physical properties of paperboards. After calendering, the roughness values of coated paperboards decreased. In addition, the obtained dot and line sharpness on calendered-coated paperboards were better than on uncalenderedcoated paperboards. However, the dot gain values of calendered-coated paperboards had fewer dot gains than uncalendered-coated paperboards. It was established that the variation of pigment proportions in the coating formulations had no significant effect on dot gain.

Correlation between Surface Energy and Adhesion Force of Polyethylene/Paperboard: A Predictive Tool for Quality Control in Laminated Packaging

Poor adhesion continues to be a problem for manufacturers of laminated packaging. Therefore, the aim of this research was to study the effect of flame treatment, the type of coating, and starch application on the adhesion force of polyethylene/paperboard. The force of adhesion was determined using the peel test method; the paper surface energy was assessed by contact angle analysis; and paperboard roughness was determined by profilometer. The flame treatment did not affect the surface roughness but significantly increased the paperboard surface energy. The paperboard coated with polar latex showed much higher surface energy than the paperboard coated with nonpolar latex. The adhesion force of polyethylene presented a linear correlation to the surface energy of the paperboard. Therefore, the surface energy of paperboard is an excellent indication of its adhesion force to polyethylene, and this represents a very reliable and practical method in terms of quality control in the paper industry for producing laminated packages.

Bilayer biocomposites based on coated cellulose paperboard with films of polyhydroxybutyrate/cellulose nanocrystals

Fil: Seoane, Irene Teresita. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingenieria. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales; Argentina

Precision scan-imaging for paperboard quality inspection utilizing X-ray fluorescence

Paperboard is typically made up of a core of cellulose fibers [C6H10O5] and a coating layer of [CaCO3]. The uniformity of these layers is a critical parameter for the printing quality. Current quality control methods include chemistry based visual inspection methods as well as X-ray based methods to measure the coating thickness. In this work we combine the X-ray fluorescence signals from the Ca atoms (3.7 keV) in the coating and from a Cu target (8.0 keV) placed behind the paper to simultaneously measure both the coating and the fibers. Cu was selected as the target material since its fluorescence signal is well separated from the Ca signal while its fluorescence's still are absorbed sufficiently in the paper. A laboratory scale setup is built using stepper motors, a silicon drift detector based spectrometer and a collimated X-ray beam. The spectroscopic image is retrieved by scanning the paperboard surface and registering the fluorescence signals from Ca and Cu. The exposure time for this type of setups can be significantly improved by implementing spectroscopic imaging sensors. The material contents in the layers can then be retrieved from the absolute and relative intensities of these two signals.

Ultraviyole Flekso Mürekkeplerin Karboksimetil Selüloz ve Polivinil Alkol ile Kaplanmış Kartonların Basılabilirlikleri Üzerindeki Etkilerinin Karşılaştırılması

The aim of this work is to compare the effect of Ultraviolet (UV) flexo inks used in the paperboards coated with carboxymethyl cellulose (CMC) and Polyvinyl alcohol (PVOH) on the printing quality. The study was made at two stages. At the first one, the surface sizing prepared using 5 % of carboxymethyl cellulose, 5 and 10 % of PVOH was coated on the surface of base paperboard and fully dried at the room temperature. The surface roughness, contact angles, cobb and gloss values of the coated base paperboard were measured. At the second stage, the test printings using both water based flexo ink and UV flexo ink on the coated base paperboard were carried out. The print density, L*a*b* and gloss values (printed) were evaluated on the printed surface areas in the coated base paperboards. The obtained results showed that the surface smoothness of the paperboards coated by PVOH was better than the one coated using CMC, but their resistance to wetting was smaller. The printing quality between the paperboards coated by PVOH or CMC was not significantly different. The print density, delta gloss and chroma values of printings attained using UV ink were higher compared to water based ink, revealing that the UV inks increased the printing quality.

Effect of heat treatment temperature on properties of electrosprayed paperboard

The purpose of this study was to investigate the effect of additional heat treatment on the properties of paperboard electrosprayed with poly(lactic acid) (PLA). For this study, paperboards electrosprayed with PLA at 1%, 2%, and 3% (w/v) were further heat‐treated at 170°C, 180°C, 190°C, and 200°C for 1 minute. Physical properties, such as basis weight, thickness, and colour of electrosprayed paperboards, were investigated. For mechanical properties, folding endurance and bursting strength of treated paperboard was tested. Water resistance property was observed through contact angle, and water absorption was monitored by Cobb test. In addition, water vapour transmission rate tests were also conducted. Surface characteristics were investigated using a scanning electron microscope and roughness tester. After heat treatment, PLA particles on the paperboard surface melted and formed a smoother continuous surface; this contributed to lower water contact angles and significantly lower water absorption. Furthermore, the higher the concentration of PLA, the better the water resistance. Moreover, heat treatment temperature between 180°C and 200°C could significantly improve the water vapour barrier and water resistance properties. Temperature and treatment time could not be further increased, as the electrosprayed paper substrate was damaged and became yellowish. In addition, for the mechanical properties, an increase in the heat treatment temperature improved the bursting strength; however, a reduction in folding endurance was observed, because the melted PLA particles were absorbed deeper into the paper structure and made the whole matrix more brittle.

Cellulose nanofiber/carboxymethyl cellulose blends as an efficient coating to improve the structure and barrier properties of paperboard

Cellulose nanofibers (CNF) have been suggested in the literature as a potential barrier coating layer for paper and paperboard. However, due to its rheological properties and solids content, the material is difficult to apply to paper at significant coat weight levels. The use of CNF as a coating to improve the structure and barrier properties of paperboard was investigated. Two forms of CNF were used: (1) refiner produced material and (2) material produced with an ultra-fine grinder. Carboxymethyl cellulose (CMC) was used for some samples as an additive. The rheology of these suspensions was characterized. These materials were applied onto the surface of paperboard using a draw-down rod coater in two layers. Scanning electron microscope (SEM) was used to see the coverage of the paper by the CNF layer. Air permeability, water penetration and barrier properties of the samples were characterized. The steady shear viscosity of CNF suspension decreased after the addition of CMC. Although CNF at 2% solid content without CMC could not be spread out onto the surface of paper uniformly, 3% CNF along with CMC was successfully coated on the surface of paper: CMC acts as a dispersant that produces a uniform suspension with minimal flocs. The ground CNF with CMC produced the best samples with good coverage as revealed by SEM images. The results show that the structure and barrier properties of coated paperboards improved considerably by the application of CNF coatings.

Effects of Calendering on Print Densities of Coated Paperboards

In this study, the effect of calendering on print quality was determined. For this purpose, five different pigment-coating formulations were prepared. They were coated on the surface of the base paperboard, previously coated with starch. Half of the coated base paperboards were calendered. Then, the Ugra82 (Ugra82 Plate Control Wedge) was printed on calendered and uncalendered-coated base paperboard surface by offset printing using black inks. All solid density measurements on the printed wedge were performed by a calibrated Gretag Macbeth Spectrolino Spectrophotometer (D50, 2 degree observer, included UV, with white backup). Double coating of the base paperboard surface is important for printability. As a result of measurement, it was found that calendering increased the surface smoothness. The surface smoothness of coated paperboard increased as long as ink absorption reduced. Hence, density value augmented after calendering. Generally, the raise of the kaolin ratio in the coating formulations affected positively printability.

Characterizing unprinted paperboard surface for predicting optically induced halftone mottle

Characterizing unprinted paperboard surface for predicting optically induced halftone mottle