Volume 39, Issue 4

The potential of oxygen delignified fibers to replace fully bleached fibers in tissue products was investigated on softwood pulps. The absorption, mechanical properties and softness of laboratory tissue hand sheets from one commercial fully bleached pulp and five unbleached oxygen delignified lab pulps were compared. The pulps with different lignin content and total fiber charge were evaluated with and without PFI refining. The pulps subjected to oxygen delignification resulted in pulps with much higher total fiber charge content that led to higher swelling and higher wet strength when compared to the commercial fully bleached pulp. Some unbleached oxygen delignified pulps showed great potential in the absorption capacity, while others showed a much higher wet tensile strength when compared to the commercial pulp. Compared to the commercial bleached pulp, a similar softness for a higher wet and dry tensile index in the unbleached fibers was observed for the oxygen delignified pulps. Unbleached pulps subjected to an extended oxygen delignification proved to be a suitable alternative to fully bleached pulps in tissue grades, depending on the desired property (absorption or wet strength).

This study investigates the impact of lignin extraction on the rheological and combustion properties of high-solids bamboo kraft black liquor (BKBL), focusing on viscosity reduction and silicon interference mitigation. Lignin was extracted from BKBL using CO 2 acid precipitation. The effects on viscosity, silicon content, calorific value, and Volumetric Isothermal Expansivity (VIE) were systematically analyzed. Extracting 25 % of lignin reduced the apparent viscosity of BKBL and achieved a 33 % desilication rate. However, this extraction also led to a proportional decrease in calorific value and VIE, with a 15 % extraction resulting in approximately 11 % and 13 % reductions, respectively. An extraction rate of 15–25 % is recommended to balance viscosity reduction and silicon removal with minimal impact on boiler combustion efficiency. This study provides practical insights into optimizing lignin extraction from BKBL, offering significant operational, economic, and environmental benefits for the bamboo kraft pulping industry.

In today’s world, the use of paper and cardboard increasing but the availability of raw materials and the environmental impact on the paper industry is a big concern. To address these concerns, researchers are exploring the potential of agricultural waste products as raw materials for pulp production. This study uses morphological, chemical composition, FTIR, XRD, and thermogravimetric analysis to examine the potential of banana pseudo-stem as a raw material for paper pulp to address environmental concerns and raw material shortages in the paper industry. The study reveals favorable characteristics for papermaking, including long fiber length (1750 μm), thin cell wall thickness (9.7 μm), and large lumen diameter (22.15 μm). The chemical composition of banana pseudo-stem contains cellulose (44.93 %), hemicellulose (23.7 %), and Klason lignin (11.1) showing its suitability for pulp production. FTIR analysis highlights the functional groups present on the banana pseudo-stem. The XRD analysis shows that it has a similar cellulosic peak and crystallinity index with common raw materials used in pulp production. The thermogravimetric analysis shows that the banana pseudo-stem has high thermal stability. The findings demonstrate that banana pseudo-stem, both by itself and in combination with other raw materials, might be a potential raw material for the pulp production.

This study investigated the use of sodium carbonate pulping in oil palm empty fruit bunch (OPEFB) pulp production for paperboard manufacturing. The pulping varying the active alkali (AA) (4.5 %, 6.5 %, 8.5 %), NaOH fraction (F) (10 %, 20 %, 30 %), and cooking time (T) (30′, 60′, 90′). The performance was evaluated based on screened pulp yield, kappa number, and delignification selectivity. Furthermore, the functional groups, S/G ratio, and morphological structure of the optimum pulp were observed. The tensile and tear indices of the OPEFB pulp paperboard were also measured. The results suggest sodium carbonate pulping at a low chemical dose successfully produced OPEFB pulp. Based on the highest delignification selectivity value of 12.74, the most effective pulping conditions were achieved with AA-6.5 %, F-30 %, and T-90′. The optimum OPEFB pulp analysis revealed a decrease in lignin proportion with the dominant degradation of the syringyl unit. Thus, the fibers are easily separable during mechanical treatment. These characteristics influenced the paperboard, resulting high tensile and tear indices of 7.90–8.15 Nm g −1 and 15.09–16.25 mN m 2  g −1 , respectively. Overall, this study demonstrated the potential of sodium carbonate pulping to produce high-quality pulp and paperboard from OPEFBs, highlighting the thoroughness of the research process in the pulp and paper manufacturing field.

Increased knowledge on the correlation between pulp processing, fibre-properties and paper properties is required to improve fibre-based products. Part 1 of this investigation deals with the effects of HC and LC refining on fibre properties development. LC refining reduced curl and increased tensile index in a manner similar to hot disintegration whereas HC refining increased curl slightly. In this second part, the correlation between fibre curl and handsheet properties of thermomechanical pulp, subjected to low consistency (LC) refining and hot/cold disintegration is examined. Fibre curl decreased by laboratory disintegration and LC refining and showed a linear correlation with increased tensile index and tensile stiffness. Evaluation of fibre property distributions gave a more detailed description of the development of fibre properties. These revealed that disintegration and LC refining gave different fibre curl versus fibre length distributions, even when their average values were similar. These results confirm that analysing fibre property distributions contributes to a more detailed knowledge of the development of pulp quality. Hot disintegration before laboratory testing exaggerated pulp quality and increase internal fibrillation and can therefore be questioned. When hot disintegration is performed before pulp analyses, the impact of LC refining on paper properties may be misjudged.

Ensuring sufficient mechanical performance while enabling lightweight design is critical for utilizing paper sandwich panels in the furniture industry. To design lightweight sandwich panels that balance mechanical properties and cost, this study developed a circular core paper sandwich panel (CCPSP) and investigated its structural efficiency using multi-objective optimization. The response surface method (RSM) based on Box–Behnken design was utilized to establish mathematical models relating the paper tube spacing, inner diameter, and height to the out-of-plane compressive strength, density, and cost. The resulting models effectively revealed the coupled effects of the parameters on the responses. Subsequently, the models were optimized using the non-dominated sorting genetic algorithm II (NSGA-II) to find the Pareto optimal trade-offs between maximizing compressive strength while minimizing its density and cost. The optimization solution resulted in an optimal set of paper tube geometries that maximized the structural efficiency of CCPSP. Overall, lower tube height conferred superior structural efficiency, while tube spacing and diameter were constrained. The results highlight the potential of CCPSP as an efficient and sustainable material for furniture manufacturing, enabled by multi-objective optimization of its structure.

The use of mineral-based fillers tends to reduce the mechanical properties of paper, which can limit their application. The filler surface modification is a significant treatment to overcome this limitation. This research aims to offer a novel modified mineral-based filler to provide its industrial application. The surface of precipitated calcium carbonate (PCC) was modified with xylan (XS), which is a type of hemicellulose, a polysaccharide consisting mainly of xylose residues. It is used as a filler at different filler dosage levels in paper pulp. Modified PCC(MPCC) was characterized with Fourier transform infrared spectroscopy, Thermogravimetric analysis, X-ray photoelectron spectroscopy, X-ray diffraction and Field-emission scanning electron microscopy analyses. The analysis demonstrated that the MPCC filler surface was coated with XS successfully. The effect of PCC and MPCC-filled hand-sheet paper physical, chemical and optical properties were studied. The experimental results showed that the mechanical (tensile, burst, tear strength) and optical (brightness, opacity) of hand-sheet paper filled with MPCC were significantly improved compared with unmodified PCC-filled paper at the same ash content. The filler retention of PCC and MPCC fillers in paper was investigated, and the MPCC filler showed better filler retention properties in paper stock than the PCC filler.

Paper is a kind of renewable material that exists widely and has important application prospects. However, previous studies have mostly focused on the macromechanical properties of paper but lack micro theory based on paper fiber networks. We present a comprehensive experimental and computational study on the mechanical properties of fibers and fiber networks under the influence of microstructure. A beam-spring model was established based on a beam-fiber network to simulate the behavior of fiber networks. Simulations were performed to demonstrate the influence of fiber microstructural parameters such as fiber bond strength, stiffness, failure strength, size, and network density on mechanical features. Mechanical experiments verified that the fiber bond strength had a greater influence on the paper properties than did the fiber strength. This result is highly consistent with that of the model. All the simulations were validated by experimental measurements. Finally, we provided computational insights into the interfiber bond damage pattern with respect to different fiber microlevels and demonstrated that the proposed beam-spring model can be used to predict the response of fiber networks of paper materials. The above research can be used to optimize the formulation, process, and treatment of paper to meet specific application needs.

The potential of combining stratified paper forming with pulp fractionation was investigated to improve the balance between low density, which enhances water absorbency and softness, and the dry strength of tissue papers. The selected fractionation approaches allowed us to separate especially stiff, low-fibrillated fibers (A fractions) from flexible, fibrillated fibers containing fines (detached segments of fibers, fibrils, or lamellae fragments) (B fractions). After characterizing the morphological properties of each fiber fraction, 20 g/m 2 model papers were produced with and without wet pressing to tune the paper density. At a density of 0.3 g/cm³, the tensile breaking stress of B papers was at least three times higher than that of A papers. The strain at break of B papers was also close to two times higher than that of A papers. Interestingly, bilayer papers A/B exhibited breaking stress values intermediate between those of A and B papers, while native pulp papers, i.e. , without fractionation and stratified forming, followed the trend of A papers. Notably, bi-layering the paper improved the breaking stress by up to twice as much without increasing the paper density, which could be highly beneficial in improving the balance of properties in tissue paper grades.

To address the challenges of difficulty and low penetration speed of aqueous deacidification agents in paper, we aimed to enhance the wetting performance of these agents by incorporating a surfactant. We selected four surfactants for our study: anionic sodium dodecyl benzene sulfonate (SDBS), cationic cetyltrimethylammonium bromide (CTAB), nonionic polysorbate-80 (TW80), and polyether-modified trisiloxane (TRSE). The wetting properties of these surfactants on sodium propionate aqueous deacidification agent, the alkali stability of the solution, and the effects of moist heat aging on paper durability were explored. The results demonstrated that TRSE exhibited superior performance compared to the other three surfactants, effectively reducing the surface tension of sodium propionate solution to 21.02 mN/m. In alkaline conditions with a pH range of 8.00–10.00, the surface tension of SDBS, CTAB, and TW80 solutions remained stable for 30 days. Similarly, under weakly alkaline conditions with a pH value below 9, the surface tension of TRSE solutions exhibited stability. It should be noted that SDBS accelerated the decline of paper tensile index and whiteness during the heat and humidity aging process; at the same time, CTAB, TW80, and TRSE had no noticeable adverse effects on paper aging resistance.

Biobased coating material is required to replace synthetic polymer-based paper coating material for a safe and clean environment. The study aimed to investigate the use of biobased nanocomposites as a coating material for paper. The biobased nanocomposite was prepared using nanocellulose, sodium alginate (SA), and bio-synthesized silver nanoparticles (AgNPs). Nanocrystalline cellulose (NCC) was produced through acid hydrolysis, followed by fractionation. The average size of the crystals was 15 nm in width and 125 nm in length. AgNPs were prepared by the reduction of AgNO 3 with lignin. The synthesis of silver nanoparticles was confirmed by UV–visible and FTIR spectroscopy. SA-NCC composite coating improved the barrier and strength properties of paper. The paper with composite coating demonstrated a 29.11 % increase in tensile index in the cross direction, 20.82 % increase in the machine direction, and 77.89 % improvement in burst index at a coating weight of 1.68 g/m 2 . The composite-coated paper showed better air barrier and lower water absorption characteristics than sodium alginate-coated paper. The incorporation of AgNPs in the coating mixture introduced the antimicrobial activity of the paper as well.

In this research we proposed and tested a solution for improving lightfastness of paperboard electrophotographic prints – enhancing the printed material with inks containing pearlescent pigments. The goal was to analyze how pearlescent pigments’ composition and the size of their particles affect lightfastness, and to assess whether this important property is influenced by the tone value of the initial ink layer. Therefore, lightfastness of the unprinted paperboard and the paperboard printed in electrophotography with medium and full coverage of black ink was measured before and after overprinting with pearlescent inks. The results indicate that pearlescent pigments can be efficiently used to prevent light induced degradation of both paperboard and the corresponding prints. The most significant improvements in lightfastness were noticed when pearlescent inks were printed directly onto the paperboard and on the prints with 50 % black coverage. The best protection from light was achieved with pigments containing only two layers – mica and ferric oxide. Pigments containing mica, titanium dioxide, and tin oxide provided satisfactory lightfastness of the printed paperboard even with the small surface coverage. No significant correlation was found between the size of pearlescent pigment particles and the lightfastness of the paperboard prints to which they are applied.

Non-Newtonian viscous fluids such as yogurt, honey, etc., due to their extremely high viscosity and complex fluidity, remain on food containers after use, where adhesion and staining occurs, which is a great inconvenience and causes a lot of wasted resources. Hydrophobic coatings can be an excellent candidate for eliminating liquid waste. Inexpensive wollastonite nanoparticles were used to build rough micro- and nano-structures, and chitosan was used to emulsify rice bran wax to prepare green and low surface energy emulsions. The above two were mechanically mixed to obtain the hydrophobic emulsion, and coated on the paper surface and heat-treated to prepare the hydrophobic paper. Contact angles up to 157.3°. The coating exhibits good self-cleaning properties for a wide range of non-Newtonian viscous food liquids and shows excellent resistance to repeated machine bending and multiple abrasion damages, while maintaining its hydrophobicity. After 40 cycles of friction, the contact angle is 148.1°, which is still close to 150° and has good hydrophobicity. In addition, the coating has great potential for application to the interior surfaces of various food packages to reduce or even eliminate liquid food residues.

Sludge generated from kraft pulp mill wastewater treatment plants (WWTPs) is typically non-inert solid waste and is commonly disposed of in landfills. In this study, a novel approach for repurposing WWTP sludge from a kraft pulp mill in Brazil for energy generation was assessed. With the global cellulose market projected to reach $ 61 billion by 2033, there is a growing need for sustainable energy solutions and disposal of associated industrial byproducts. This study investigated the performance of a hybrid active solar dryer for reducing the moisture content of sludge to enhance the feasibility of sludge burning in a biomass boiler. Through rigorous experimentation and design of experiments (DOE) planning, optimal parameters for the hybrid dryer were determined, specifically, a volumetric airflow rate of 1.1 m/s and an entrance temperature of approximately 51 °C. This innovative approach not only addresses the environmental concerns associated with sludge disposal, but also contributes to the broader goal of advancing sustainable technologies in the midst of global energy challenges.

Ionic liquids (ILs) are potentially alternative solvents for cellulose dissolution. In this article, effect of hemicellulose in cellulose dissolution in ILs and the regeneration process were investigated. Hardwood pulps were produced by kraft (KP) and pre-hydrolysis kraft (PHKP) processes. The α-cellulose and residual pentosan contents were 95.6 % and 4.2 % in PHKP and 84.3 % and 9.9 % in KP, respectively. Both pulps were dissolved in 1-butyl-3-methylimidazolium chloride [C 4 mim]Cl, 1-butyl-3-methylimidazolium acetate [C 4 mim]CH 3 CO 2 and their double salt (DSIL), [C 4 mim](CH 3 CO 2 ) 0.6 Cl 0.4 at 90 °C. It was observed that PHKP had slightly higher solubility in both ILs and DSIL. The dissolved pulps were regenerated by water and characterized by FTIR, TGA, X-ray diffraction, and viscosity. Regenerated pulp film formed smooth and homogenous surface. The viscosity of regenerated PHKP was higher than the original PHKP, which affected the strength of the produced cellulose film. As observed in FTIR, the regenerated cellulose showed a stronger absorption band at 1,647 cm −1 corresponding to the C–O stretching vibration of C–O–H. The crystalline structures of regenerated KP and PHKP from [C 4 mim](CH 3 CO 2 ) 0.6 Cl 0.4 changed to cellulose II form from the original cellulose I form.

In order to fully utilize industrial lignin, a comparative study was conducted on the properties of porous carbon electrodes prepared by activating different industrial lignin as precursors. The results revealed that carbon electrodes prepared with sodium lignosulfonate (CM-S) exhibited superior specific surface area (SSA) (1,593.5 m 2  g −1 ) and pore volume (PV) (1.03 cm 3  g −1 ) due to the largest relative molecular mass (Mn = 4,539, Mw = 7,290), which is greater than that prepared with alkali lignin (CM-A) and kraft lignin (CM-K), and displayed a well-developed micro-mesoporous macropore hierarchy which was feasible for the efficiency of electron mobility. The electrochemical properties of materials were evaluated, and CM-S showed a mass-specific capacitance of 201 F g −1 at 0.2 A g −1 current density, along with an impressive capacitance retention rate of 54.7 % at 10 A g −1 current density, which is more potential than CM-A and CM-K (specific capacitances: 100 F g −1 and 75 F g −1 respectively). Additionally, maximum energy and power density of CM-S were measured to be 6.98 W h kg −1 and 2306 W kg −1 with excellent retention rate of 95.5 % after 10,000 charge–discharge cycles at a current density of 5 A g −1 . Comparatively, sodium lignosulfonate, compared with alkali lignin and kraft lignin, emerges as a more ideal precursor material for porous carbon electrode.

Phenolic hydroxyl groups in lignin are crucial for understanding its structure, reactivity, and potential applications. Various methods have been developed for the determining phenolic groups in lignin. This study focuses on the comparison of a simple, cost-effective, and time-efficient UV–vis ionization difference technique with the highly accurate 31 P NMR spectroscopy for analyzing lignin samples of different origins and isolation methods. The results were carefully evaluated, and the strengths and limitations of each method were discussed. Two eco-friendly UV–vis approaches were proposed for a rapid and comprehensive evaluation of the total phenolic-OH groups: one using a strong alkaline solution for analyzing common types of technical lignins, and another employing multipoint wavelength calculations, effective for analyzing softwood lignins regardless of the extraction method. Additionally, the research highlighted the importance of selecting appropriate model phenolic compounds to accurately assess the phenolic hydroxyl group content in lignins using the UV–vis method. Offering straightforward and rapid analysis, with results closely aligning with 31 P NMR data, this method is a promising alternative for routine analysis.

Weave and drainage marks on paper surfaces derived from forming fabrics installed in paper machines were examined. Non-destructive differentiation of copy papers from various manufacturers was performed by a 2D Lab Formation Sensor. Individual characteristics such as angles and wavelengths formed by the fabric were selected as parameters for the analysis. These parameters were sampled from a total of 500 papers: 50 sheets of paper from each of the 10 groups by copy paper manufacturers. Using machine learning algorithms such as partial least squares discriminant analysis (PLS-DA), k-nearest neighbors (k-NN), and naive bayes (NB) models to analyze these parameters allows for the identification of copy paper groups by manufacturers. The NB classifier demonstrated superior performance, achieving an accuracy of 0.973 even with a 50 % reduction in input variables. This study shows that periodic marks on paper surfaces can act as important indicators of the forming fabric and the distinct features of a paper-making machine. In general, this paper proposes that the 2D Lab Formation Sensor along with machine learning models can be utilized for non-destructive copy paper categorization. This identification method could be broadened to determine information regarding suspicious documents for forensic identification purposes.