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All-lignin coating formulations were prepared while combining water-soluble cationic kraft lignin (quaternized LignoBoost®, CL) and anionic lignosulphonate (LS). The electrostatic attraction between positively charged CL and negatively charged LS led to the formation of insoluble self-organized macromolecule aggregates that align to films. The structures of the formed layers were evaluated by atomic force microscopy (AFM), firstly on glass lamina using dip-coating deposition and then on handsheets and industrial uncoated paper using roll-to-roll coating in a layer-by-layer mode. Coated samples were also characterized by optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (SEM/EDS), and contact angle measurements. It was suggested that the structure of all-lignin aggregates is the result of the interaction of amphiphilic water-soluble lignin molecules leading to their specifically ordered mutual arrangement depending on the order and the mode of their application on the surface. The all-lignin coating of cellulosic fiber imparts lower air permeability and lower free surface energy to paper, mainly due to a decrease in surface polarity, thus promoting the paper's hydrophobic properties. Moderate loading of lignin coating formulations (5–6 g m−2) did not affect the mechanical strength of the paper. [ABSTRACT FROM AUTHOR]

The study describes the preparation of nanocellulose from organosolv hemp pulp and its application in the production of food packaging paper as an alternative to petroleum products. OHP was obtained from renewable plant materials hemp fibers by extraction with NaOH solution and cooking using a mixture of acetic acid and hydrogen peroxide. A stable transparent nanocellulose gel was extracted from OHP by acid hydrolysis followed by ultrasonic treatment. It was found that an increase in the consumption of sulfuric acid, temperature and duration of the OHP hydrolysis process improved the quality indicators of hemp nanocellulose. A linear dependence of the tensile strength and transparency of nanocellulose films on their density has been established. Morphological (SEM), structural (FTIR and XRD) and thermal analysis (TGA) of hemp fibers, OHP and nanocellulose were carried out. Nanocellulose films had a density of up to 1.56 g/cm3, a tensile strength of up to 66.7 MPa, a transparency of up to 87.3%. Atomic force microscopy method showed that the transverse dimension of nanocellulose particles is from 8 to 23 nm. Hemp nanocellulose had a higher crystallinity index (87.2%) than OHP (72.0%), but lower thermal stability. The positive effect of adding nanocellulose from hemp on improving all quality parameters of paper for food packaging has been shown. The addition of 2% hemp nanocellulose makes it possible to obtain paper that exceeds the breaking force requirements of premium grade paper by 40%, and the breaking length increases by 42% compared to paper without chemical additives. [ABSTRACT FROM AUTHOR]

Paper aging and protection processes play an essential function in the preservation of library collections and archives. In this study, some physical-mechanical properties of paper samples from XXth century books (private collections), such as pH acidity, tensile strength, and modulus of elasticity, as well as optical properties, such as absolute change in yellowness, were examined before and after treating them with hydroxyapatite nanoparticles (HAp). Accelerated light aging was also evaluated and discussed. The treatment with HAp nanoparticles increased the paper's pH to slightly alkaline values (approximately pH 8). Washing and treating the paper improved its mechanical properties compared to untreated paper; the tear length increased by 35% and the modulus of elasticity increased by 56%. That the treated and aged samples are more elastic than the original samples demonstrates that HAp nanoparticles consolidated the cellulose fibers. Additionally, particle morphology, size, composition and size distribution were assessed via image analysis using scanning electron microscopy (SEM-EDX), atomic force microscopy (AFM), and the ImageJ processing program. [ABSTRACT FROM AUTHOR]

The cost of specialized scientific equipment can be high and with limited funding resources, researchers and students are often unable to access or purchase the ideal equipment for their projects. In the fields of materials science and mechanical engineering, fundamental equipment such as tensile testing devices can cost tens to hundreds of thousands of dollars. While a research lab often has access to a large-scale testing machine suitable for conventional samples, loading devices for meso- and micro-scale samples for in-situ testing with the myriad of microscopy tools are often hard to source and cost prohibitive. Open-source software has allowed for great strides in the reduction of costs associated with software development and open-source hardware and additive manufacturing have the potential to similarly reduce the costs of scientific equipment and increase the accessibility of scientific research. To investigate the feasibility of open-source hardware, a micro-tensile tester was designed with a freely accessible computer-aided design package and manufactured with a desktop 3D-printer and off-the-shelf components. To our knowledge this is one of the first demonstrations of a tensile tester with additively manufactured components for scientific research. The capabilities of the tensile tester were demonstrated by investigating the mechanical properties of Graphene Oxide (GO) paper and thin films. A 3D printed tensile tester was successfully used in conjunction with an atomic force microscope to provide one of the first quantitative measurements of GO thin film buckling under compression. The tensile tester was also used in conjunction with an atomic force microscope to observe the change in surface topology of a GO paper in response to increasing tensile strain. No significant change in surface topology was observed in contrast to prior hypotheses from the literature. Based on this result obtained with the new open source tensile stage we propose an alternative hypothesis we term ‘superlamellae consolidation’ to explain the initial deformation of GO paper. The additively manufactured tensile tester tested represents cost savings of >99% compared to commercial solutions in its class and offers simple customization. However, continued development is needed for the tensile tester presented here to approach the technical specifications achievable with commercial solutions. [ABSTRACT FROM AUTHOR]

The purpose of this article is to evaluate the potential risk of exposure to nanoparticles of workers in paper mills. In the final stage of the paper production, the very large sheets are wound onto large reels, where these are processed depending on their ultimate use. Paper is smoothed and compacted by passing through metal rollers. During these mechanical treatments nanometric ultrafine particles are generated. In particular, the nanoparticle presence, size and morphology were investigated and differences between particles produced either in summer or winter seasons were explored. To this aim Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS) were employed to analyze nano powders filtered in environments of different paper mills to determine structural morphology and sizes. Large breathable particles, with size in the range from 4 μm to 250 nm have been sampled to evaluate the mean level of exposure. By comparing nanoparticles collected from paper mills in summer and in winter we revealed that the number of nanoparticles collected in winter is strictly related to heat generated by the heating system. [ABSTRACT FROM AUTHOR]

The paper deals with the precision control for the parameters of manufactured paper production, such as various kinds of paper and photo paper for printing. Research of untreated, matte, glossy and laminated paper is conducted by atomic force microscopy by means of educational and scientific scanning probe microscope NanoEducator LE in the framework of this paper. Visualization of characteristic structure for each type of studied paper was conducted, histogram of roughness was obtained, and average roughness of height differences was defined. A laminated paper has got the lowest roughness (Ra of about 70 nm) and glossy paper has got Ra of about 170 nm; roughness of untreated paper with cellulose fibers is about 530- 540 nm, and matte paper has got the highest roughness parameters (Ra about 670-680 nm). Scanning probe microscopy application for parameters monitoring of cellulosic paper production is shown to give the possibility of such microscopy type application in the production of paper products and high-precision control of its parameters.

In parallel with the development of nanoparticle coatings for protection of paper substrates, detailed descriptions of the surface topography with micro- to nanoscale roughness features are needed. In this work, papers have been coated with poly(styrene-co-maleic anhydride) nanoparticles including different types of vegetable oils and the surface roughness was evaluated at 2000 × 2000 μm 2 to 0.2 × 0.2 μm 2 length scales by combining non-contact optical profilometry (NCP) and atomic force microscopy (AFM). The relationships between roughness data were studied for statistical roughness parameters, spatial roughness parameters and in the frequency domain. In order to compare AFM roughness more accurately, the original images were flattened to remove effects of the underlaying fibrous substrate and highlight features of the nanoparticle coating. More detailed information on the coating topography could be obtained by considering bearing ratio curves and histograms, where it was concluded that the oil-filled coatings form a rather thin and continuous coating that closely follows the shape of the cellulose fibers. The relation between statistical roughness parameters from NCP and AFM follows an exponential trend with relatively low coefficient of determination. The increase in surface roughness with length scale showed a transition point attributed to short- and long-range surface features. Therefore, the correlation length was used as a spatial roughness parameter that provides a successful extrapolation of the average roughness over different length scales in a double logarithmic diagram with very high coefficient of determination. Based on the power spectral density, it was difficult to exactly distinguish between the different types of SMI/oil coatings, as they include similar nanoscale features. The frequency roughness parameters were better suited for extrapolation than statistical roughness parameters but little less efficient than the spatial roughness parameters. [ABSTRACT FROM AUTHOR]

Corona, flame, atmospheric plasma, and liquid flame spray (LFS) techniques were used to create highly hydrophilic surfaces for pigment-coated paper and board and machine-glossed paper. All the surface modification techniques were performed continuously in ambient atmosphere. The physical changes on the surfaces were characterized by field emission gun-scanning electron microscopy (FEG-SEM), atomic force microscopy and Parker Print-Surf surface roughness. The chemical changes were analysed by X-ray photoelectron spectroscopy. The superhydrophilic surfaces, i.e. contact angle of water (CAW) <10°, were created mainly by modifying the surface chemistry of the paper and board by argon plasma or SiO2coating. The nano- and microscale roughness existing on paper and board surfaces enabled the creation of the superhydrophilic surfaces. Furthermore, the benefits and limitations of the surface modification techniques are discussed and compared. For example, the SiO2coating maintained its extreme hydrophilicity for at least six months, whereas the CAW of argon plasma-treated surface increased to about 20° already in one day. [ABSTRACT FROM AUTHOR]

Vegetable oils were combined with recent nanotechnology as a sustainable method for tuning the hydrophobicity of cellulose and paper surfaces. Different soy-, sunflower-, corn-, castor-, rapeseed- and hydrogenated oils were incorporated into an aqueous dispersion of hybrid styrene maleimide nanoparticles. Here, we investigate the formation of novel coatings from these dispersions and their performance on paper and paperboard, compared with model aluminum substrates. The coated papers are evaluated by static and dynamic contact angles, microscopy, atomic force microscopy, infrared and Raman spectroscopy. The nanoparticle pigments form a porous coating after drying, while the water repellence and hydrophobicity of paperboard and paper improved with contact angles of 90-99° after drying and 98-112° after ageing. The coatings with poly(unsaturated) oils have best hydrophobicity for dispersions with an optimum viscosity of 115-150 cp required for good coverage of the paper. While homogeneous coverage of the cellulose fibers is a primary requirement, thin coatings often provide higher contact angles on paper due to roughness of the underlaying fibrous surface. After ageing, the coatings are chemically stable without oil leakage and constant imide content, while an increase in contact angles is attributed to variations in coating morphology through local re-arrangements over the paper substrate. [ABSTRACT FROM AUTHOR]

Paper, a man-made material that has been used for hundreds of years, is a network of natural cellulosic fibres. To a large extent, it is the strength of bonding between these individual fibres that controls the strength of paper. Using atomic force microscopy, we explore here the mechanical properties of individual fibre-fibre bonds on the nanometre scale. A single fibre-fibre bond is loaded with a calibrated cantilever statically and dynamically until the bond breaks. Besides the calculation of the total energy input, time dependent processes such as creep and relaxation are studied. Through the nanometre scale investigation of the formerly bonded area, we show that fibrils or fibril bundles play a crucial role in fibre-fibre bonding because they act as bridging elements. With this knowledge, new fabrication routes can be deduced to increase the strength of an ancient product that is in fact an overlooked high-tech material [ABSTRACT FROM AUTHOR]

The penetration of ink into paper affects the final appearance of printing and the amount of ink usage. In this work, UV-curing fluorescent rose ink was used to investigate the penetration and distribution of the ink pigments as well as their correlation with the surface topography of paper. The ink penetration and distribution were characterized with Confocal Laser Scanning Microscopy (CLSM), whereas the microstructure of the paper surface was observed using Atomic Force Microscopy (AFM). The AFM results showed that the surface of the paper coated with kaolin layer was the smoothest among the samples. Also the pore size of the calcium carbonate coating layer was smaller than that of the kaolin coating layer. Meanwhile, the pore size distribution of the calcium carbonate coating layer appeared to be relatively narrow, compared with other samples. The results of CLSM images indicated that the depth, size, and arrangement of pores affected the penetration depth and distribution of ink pigment on coated paper. The large pores led to deeper penetration of ink pigments, and uniform ink absorption occurred when the pore distribution was uniform. The UV-curing ink pigments not only set on the surface of the uncoated paper, but also they penetrated into the paper interior and adhered to the fiber surface. [ABSTRACT FROM AUTHOR]

Nanoparticles of partially imidized poly(styrene-maleic anhydride) were applied from an aqueous dispersion as a one- or two-layer coating onto paper substrates, for controlling the paper surface hydrophobicity and improving the water barrier resistance. The effect of deposition conditions and thermal treatments on the topography and properties of the coating was studied by scanning electron microscopy, atomic force microscopy (AFM), contact angle measurements, and friction measurements. The wettability of paper surfaces with adsorbed nanoparticles can be controlled by tuning the chemical and topographical surface parameters: the water contact angles were found to increase at higher imide content as determined by Raman spectroscopy (depending on synthesis and thermal treatment), and higher average surface roughness determined by AFM (depending on the deposition method). The present technique may serve as a unique replacement for chemical treatments hydrophobizing fibrous substrates. [ABSTRACT FROM AUTHOR]

Abstract: Papers have a complex hierarchical structure and the end-user functionalities such as hydrophobicity are controlled by a finishing layer. The application of an organic nanoparticle coating and drying of the aqueous dispersion results in an unique surface morphology with microscale domains that are internally patterned with nanoparticles. Better understanding of the multi-scale surface roughness patterns is obtained by monitoring the topography with non-contact profilometry (NCP) and atomic force microscopy (AFM) at different sampling areas ranging from 2000μm×2000μm to 0.5μm×0.5μm. The statistical roughness parameters are uniquely related to each other over the different measuring techniques and sampling sizes, as they are purely statistically determined. However, they cannot be directly extrapolated over the different sampling areas as they represent transitions at the nano-, micro-to-nano and microscale level. Therefore, the spatial roughness parameters including the correlation length and the specific frequency bandwidth should be taken into account for each measurement, which both allow for direct correlation of roughness data at different sampling sizes. [Copyright &y& Elsevier]

Abstract: Electrodeposition of poly(3,4-ethylenedioxythiophene) doped with chloride (PEDOT-Cl) on a paper substrate is demonstrated. A fully printed silver/polyaniline (Ag/PANI) layer-by-layer structure on a pigment coated paper acted as a working electrode, on which a layer of PEDOT-Cl was galvanostatically grown in an electrochemical cell. The deposited PEDOT-Cl appeared as a dark-blue circular area on a green Ag/PANI electrode. The electrodeposition was further confirmed by chemical and topographical analyses. The results demonstrate the potential of low-cost paper substrates and roll-to-roll mass-manufacturing methods in electrochemical applications. [ABSTRACT FROM AUTHOR]

The surface properties of paper depend not only on the fibrous matrix but also on the final treatment of the paper surface. The present work compares paper samples with two different surface sizing treatments by using AFM and profilometry to assess topography and roughness parameters as well as to evaluate the spreading of the sizing formulation and to estimate sizing agent particle sizes. The results were confronted with dynamic light scattering measurements regarding particle size. This work shows that AFM is a valuable technique to visualize and quantify the effects of sizing on the paper surface. Due to the small amount of surface sizing applied, no significant differences between the surface sized samples and the reference sample (without surface treatment) could be detected in terms of the surface roughness parameters. Nonetheless, those of sample B1 are systematically smaller than those of sample A1. [ABSTRACT FROM AUTHOR]

Abstract: The surface chemical and physical character of offset paper was studied before and after application of model fountain solutions based on isopropyl alcohol and an alcohol-free surfactant solution. The paper surface features were characterised with atomic force microscopy and the surface energies were determined by contact angle measurements. Changes in the surface chemical properties induced by the fountain solutions were investigated with X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. Coated papers wetted with the surfactant solution revealed a slight increase in the root mean square roughness, but the isopropyl alcohol solution led to no observable changes. The change in sub-micro roughness is ascribed not only to substrate swelling or migration of coating constituents but also to the presence of surfactant on the surface. A change in the surface energy and particularly the polar contribution was observed after application of the surfactant solution. The X-ray photoelectron spectroscopy showed an increase in the oxygen-to-carbon ratio, which confirms the presence of surfactant on the surface. Time-of-flight secondary ion mass spectroscopy showed that the isopropyl alcohol solution did not change the elemental composition of the surface whereas the surfactant solution clearly did so. The distribution of surfactant on the surface was confirmed by mapping the characteristic fragments of the molecule. [Copyright &y& Elsevier]

AbstractSamples of two historical papers from the late 17th and early 18th centuries were irradiated with a 350-nm ?maxlight source. Atomic force microscopy examination of untreated samples of these laid paper sheets revealed notable surface inhomogeneity. Diffuse brightness values show that irradiation resulted in an initial decrease followed by a rapid increase in brightness with increasing irradiation time from 0.5 to 28 h. The bleaching effect then slowed, following a logarithmic path that did not plateau within 197 h of irradiation time. Irradiated sheets stored for 3 months exhibited brightness reversion of 7%. Fluorescence also decreased with irradiation time if excitation wavelengths of 320, 350, and 400 nm were applied for samples exposed to narrow-band irradiation at 350 nm. The fold endurance decreased by 34–72% after 197 h of irradiation. Changes in tear and tensile values were less dramatic. The Z-direction ultrasonic velocity decreased after 197 h of irradiation; however, the ultrasonic conductivity partially recovered during 9 months of storage. [ABSTRACT FROM AUTHOR]

Abstract: The spreading and recoiling of water drops on several flat and macroscopically smooth model surfaces and on sized paper surfaces were studied over a range of drop impaction velocities using a high-speed CCD camera. The water drop spreading and recoiling results on several model hydrophobic and hydrophilic surfaces were found to be in agreement with observations reported in the literature. The maximum drop spreading diameter for those model surfaces at impact was found to be dependent upon the initial drop kinetic energy and the degree of hydrophobicity/hydrophilicity of the surface. The extent of the maximum drop recoiling was found to be much weaker for hydrophilic substrates than for hydrophobic substrates. Sized papers, however, showed an interesting switch of behaviour in the process of water drop impaction. They behave like a hydrophobic substrate when a water drop impacts on it, but like a hydrophilic substrate when water drop recoils. Although the contact angle between water and hydrophilic or hydrophobic non-porous surfaces changes from advancing to receding as reported in literature, the change of contact angle during water impact on paper surface is unique in that the level of sizing was found to have a smaller than expected influence on the degree of recoil. Atomic force microscopy (AFM) was used to probe fibres on a sized filter paper surface under water. The AFM data showed that water interacted strongly with the fibre even though the paper was heavily sized. Implications of this phenomenon were discussed in the context of inkjet print quality and of the surface conditions of sized papers. Results of this study are very useful in the understanding of inkjet ink droplet impaction on paper surfaces which sets the initial condition for ink penetration into paper after impaction. [Copyright &y& Elsevier]

Cellulose is a promising biomass material suitable for high volume applications. Its potential lies in sustainability, which is becoming one of the leading trends in industry. However, there are certain drawbacks of cellulose materials which limit their use, especially their high wettability and low barrier properties, which can be overcome by applying thin coatings. Plasma technologies present a high potential for deposition of thin environmentally friendly and recyclable coatings. In this paper, two different plasma reactors were used for coating two types of cellulose-based substrates with hexamethyldisiloxane (HMDSO). The changes in surface characteristics were measured by atomic force microscopy (AFM), scanning electron microscopy (SEM), surface free energy and contact angles measurements, X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS). Successful oleofobization was observed for an industrial scale reactor where pure HMDSO was used in the absence of oxygen. [ABSTRACT FROM AUTHOR]