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Flow and spontaneous imbibition phenomena in porous media are important for various industrial applications, including printing and medical lateral flow assays. Their quantitative characterization is important to better understand and select the appropriate raw materials. However, standard methods often require time-consuming tests, and/or expensive equipment. Different time scales must be considered, limiting the range of possible characterization tools. A novel experimental approach based on image analysis for characterizing spontaneous imbibition processes is presented. Hence, ultra-fast diffusion may be quantitatively characterized. Models are issued from the literature to consider physical phenomena at small (milliseconds) and medium range (seconds) of time scales. The obtained experimental data fit with theoretical results, providing valuable insights into the understanding of fluid flow behavior at different time scales. Furthermore, the identification of some physical properties for either the fluid, or the substrate, based on the theoretical models are possible, as the contact angle, which remains to be otherwise challenging. This study contributes to bridging the gap between spontaneous imbibition and capillary phenomena at different time scales, their modeling, and a characterization of material and/or fluid properties paving the way for enhanced understanding and control of fluid behavior in porous media. Different papers are considered to illustrate the method. [ABSTRACT FROM AUTHOR]

The overall usefulness of the bursting energy absorption (BEA) was studied for a better analysis of paper strength properties. Additionally, the changes of the BEA during more complex deformations of paper products, e.g., preliminary or simultaneous tensile and burst, were determined. For the purpose of the research, an experimental setup was designed. The results showed that the correlation between BEA and bursting strength was linear, but the proportionality strongly depended on paper grade. Thus, a more accurate method to characterize the bursting resistance (BR) of paper was proposed. The BR parameter is described by the three following parameters: average bursting strength, average bursting energy absorption, and the slope of the fitted linear regression curve (relationship between the bursting energy absorption and the bursting strength). This method revealed new mechanical behaviors of papers related to their preloading. [ABSTRACT FROM AUTHOR]

A new coating method was developed, based on cellulose regenerated from an N-methylmorpholine N-oxide (NMMO) solution applied to paper. In particular, the purpose of this study was to compare the effectiveness of the "deep coating" method using cellulose regenerated from NMMO solution and the classic pulp refining process as methods to improve paper mechanical properties and overall quality. The "deep coating" name comes from the fact that the coating process is combined with subsequent heating of the coating before its final solidification. As a result of this operation, deep penetration of the cellulosic solution into the paper structure occurs. This increases the contact surface of the solution with the cellulosic fibers, which increases the strength properties of the paper structure. It was found that the cellulosic coating increased the apparent density of the paper, the tensile strength, the elongation, the resistance to bursting, and the double fold number. However, the coating also decreased the air permeability and the tear resistance of the paper samples. Despite some technological difficulties, this method could be an attractive solution in the case of a need for additional functionalization of a paper structure. [ABSTRACT FROM AUTHOR]

• Definition of the Degree of Pulp Refining Controllability (DOPRC) was proposed. • DOPRC values can vary from 0 to 100%. • Calculated Degree of Pulp Refining Controllability for tested pulp was equal to 8%. • Refining process is more controllable as the pulp development progresses. • Refining process should be constantly adjusted according to the current pulp development. Pulp refining process is considered as the most important unit operation in paper technology. Despite the simple principle of this process, it is a complex operation and not yet fully understood. It is difficult to control it thus the overall process has not been optimized so far. In the presented work, the low-consistency refining of softwood chemical pulp was investigated. The main objective of the presented research was to define a Degree of Pulp Refining Controllability (DOPRC) and to develop the method for calculation of this factor. Possible DOPRC values are between 0 and 100%. It was found that for the tested pulp, the overall DOPRC was equal to about 8%. Analysis of DOPRC changes with respect to the development of paper properties and paper web drainability suggests that the technological parameters of the process should be constantly adjusted according to the current level of refined pulp development. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Novel method of measuring the uniformity of liquid penetration through fibrous porous materials was proposed. • Texture entropy and contrast were taken into account in the proposed method. • Correlations between the dynamics of liquid penetration and the examined texture parameters were found. • New parameters were introduced for better evaluation of the nature of the liquid flow through the porous material structure. The interaction of liquids with materials is an important factor influencing many technological processes and describing the quality of the material itself. However, characterization of the wetting and penetration of liquids phenomena through the materials of heterogeneous structure is a very difficult task. Paper is an example of such material. Paper sizing is one of the most important operations in paper technology. Its purpose is to reduce the wettability of the paper. The aim of the present study was to evaluate the suitability of the texture analysis to assess the uniformity of liquid penetration through the paper structure in terms of the degree of the paper sizing. As a result of the research, a new method of measuring was proposed based on dynamic changes in their texture parameters. For this purpose, such texture parameters as entropy and contrast were used. Characteristic points were determined on the curves of the dynamic changes of both parameters. It was proved that there is a correlation between the dynamics of liquid penetration through the paper structure and the examined texture parameters. It was found that the maximum value of entropy and contrast, the time of reaching both values, the points of inflection of the curves during their decrease, and the times by which these points were reached can be useful parameters that provide information about the nature of the liquid flow through the porous material structure. [ABSTRACT FROM AUTHOR]

Hydrophobic properties belong to the most important factors which determine functional properties of paper products. A number of methods related to the measurement of the interaction between water and paper are already used but most of them give results after specific period of time whereas many unit operations in modern industrial processes (e.g. printing) last usually less than one second. As a result, most of the existing methods are not corresponding to today’s requirements. The aim of the presented research was to develop the method based on image analysis for measuring the dynamics of penetration and permeation of liquid through paper. Special device named eXtended Liquid Penetration Analyser (XLPA) was built for this purpose. Based on the obtained results, the method developed allows to observe and analyse the dynamics of liquid permeation through paper. The proposed method fully replaces the method implemented in the PLG Sizing Tester, which estimated the time of a 50% decrease in brightness of a tested paper sample permeated by ink. Presented method offers the possibility of quantitative measurement of changes in liquid absorption with time resolution of 1/60 s. At the same time, thanks to the use of a camera and image analysis, it is possible to detect local areas of non-homogeneity in paper structure that differ with regards to their capability to absorb liquid, as well as to determine quantitative measures that characterize the non-homogeneity of the permeation process with reference to paper surface. [ABSTRACT FROM AUTHOR]

Specific Edge Load (SEL) and Specific Energy Consumption (SEC) are nowadays the most popular parameters for defining the intensity of pulp refining. As a result, these factors are widely used in industrial practice. The purpose of this research was to determine limitations connected with use of these parameters during bleached kraft pulp refining. Performed tests showed that, despite keeping the SEL and SEC at constant level, changes of pulp refiner consistency always modified the character of the refining process. Obtained results showed that neither SEL nor SEC are fully reliable parameters to describe and to control the refining process. [ABSTRACT FROM AUTHOR]

This work reports a modification of a fibrous cellulose material (paper) by the addition of polyacrylonitrile (PAN) fibres doped with 10,12–pentacosadiynoic acid (PDA). The fibres are sensitive to ultraviolet (UV) light. When the paper containing PAN–PDA is irradiated with UV light it changes colour to blue as a consequence of interaction of the light with PDA. The colour intensity is related to the absorbed dose, content of PAN–PDA fibres in the paper and the wavelength of UV radiation. The features of the paper are summarised after reflectance spectrophotometry and scanning microscopy analyses. All the properties of the modified paper were tested in accordance with adequate ISO standards. Moreover, a unique method for assessing the unevenness of the paper surface and the quality of printing was proposed by using a Python script (RGBreader) for the analysis of RGB colour channels. The modification applied to the paper can serve as a paper security system. The modified paper can act also as a UV radiation indicator. [ABSTRACT FROM AUTHOR]

Starch is an inexpensive, easily accessible, and widespread natural polymer. Due to its properties and availability, this polysaccharide is an attractive precursor for sustainable products. Considering its exploitation in adhesives and coatings, the major drawback of starch is its high affinity towards water. This study aims to explain the influence of the silane-starch coating on the hydrophobic properties of paper. The analysis of the organosilicon modified starch properties showed an enhanced hydrophobic behavior, suggesting higher durability for the coatings. Molecules of silanes with short aliphatic carbon chains were easily embedded in the starch structure. Longer side chains of silanes were primarily localized on the surface of the starch structure. The best hydrophobic properties were obtained for the paper coated with the composition based on starch and methyltrimethoxysilane. This coating also improved the bursting resistance and compressive strength of the tested paper. A static contact angle higher than 115° was achieved. PDA analysis confirmed the examined material exhibited high barrier properties towards water. The results extend the knowledge of the interaction of silane compositions in the presence of starch. [ABSTRACT FROM AUTHOR]

This article describes how crystalline or fibrous nanocellulose influences the mechanical properties of paper substrate. In this context, we used commercially available cellulose nanocrystals, mechanically prepared cellulose nanofibers dispersed in water or ethanol, and carboxy cellulose nanofibers. Selective reinforcement of the paper treated with the nanocellulose samples mentioned above was observed. The change in the fibre structure was assessed using scanning electron microscopy, roentgenography, and spectroscopy techniques. In addition, the effect of nanocellulose coating on physical properties was evaluated, specifically tensile index, elongation coefficient, Elmendorf tear resistance, Bendtsen surface roughness, Bendtsen air permeability, and bending strength. It can be concluded that the observed decrease in the strength properties of the paper after applying some NC compositions is due to the loss of potential disturbances in hydrogen bonds between the nanocellulose dispersed in ethanol and the paper substrate. On the other hand, significantly increased strength was observed in the case of paper reinforced with nanocellulose functionalized with carboxyl groups. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lanthanide-doped core@shell nanoparticles for luminescent cellulose fibers production. • Dual-range excitation of luminescent materials with 975 and 1532 nm laser radiation. • Luminescent fibers as anti-counterfeiting agents for documents, clothes and valuable products. • '3-level' protection system resulting from a unique optical activity of the nanoparticles. The increasingly wide-spreading falsification of documents, clothing, and packaging has a negative impact on every aspect of the global markets. Therefore, the development of high-quality strategies for materials protection has become a big challenge. Thus, this work presents novel anti-counterfeiting lyocell fibres, exhibiting bright green or yellowish up-conversion emission upon dual-range excitation, using either 975-nm or 1532-nm NIR laser radiation. The up-converting cellulose fibers were prepared by introducing lanthanide-doped core@shell nanoparticles β-NaYF 4 : Yb3+, Er3+@β-NaYF 4 into the cellulose matrix. The spinning process of fibres was based on N-methylmorpholine N-oxide method, environmentally friendly because of the reusable reagents used. The prepared fibres were incorporated into the paper mass, forming a luminescent paper as a proof of concept for the multi-modal protection of documents. The luminescent fibres have considerable application potential as anti-counterfeiting composite materials with excellent performance, which are very difficult to imitate or copy, providing a very high level of security. [ABSTRACT FROM AUTHOR]