Volume 37, Issue 3

Amounts of wood chemical components (organic solvent extracts, Klason lignin, and holocellulose) and kraft pulp characteristics (yield and kappa number) were directly determined for 32 trees from eight half-sib Eucalyptus camaldulensis Dehnh. families in second generation of elite trees selected in Thailand. The mean values of all trees were 1.4 % for organic solvent extracts, 21.3 % for Klason lignin, 86.1 % for holocellulose, 44.4 % for kraft pulp yield, and 7.2 for kappa number, respectively. While repeatability values of growth traits and basic density were moderate to high (0.18 to 0.51), those in wood chemical components and kraft pulp characteristics showed quite low values (less than 0.10). No correlation coefficients were found between measured traits, except between stem diameter and tree height. Thus, it is concluded that selection of E. camaldulensis families with superior growth traits is suitable for production of raw material of pulp and paper in respect to quantity and quality of wood.

We present a feasible method to produce coated papers with long-lasting presence of natural active compounds. First, the composition of essential oils from Eucalyptus globulus was analyzed by gas chromatography-mass spectrometry (GC-MS), revealing high proportions of eucalyptol (73 %) and α-pinene (15 %) in the case of the leaves, and sesquiterpenoids like globulol and epiglobulol (55 %) for the wood essential oil. These compounds were incorporated onto paper sheets by conventional coating processes, using surface starch as binder. Nonetheless, the main source of novelty lies in the functionalization of starch with β-cyclodextrin by two-step esterification, resulting in enhanced binding capabilities. Release to air was evaluated by headspace-solid phase microextraction, using a divinylbenzene/Carboxen/polydimethylsiloxane fiber, whose adsorbates were analyzed by GC-MS. One week after coating a paper sheet with native starch and essential oil from E. globulus , terpineol, eucalyptol and pinene were below the limit of detection. The insertion of cyclodextrin moieties improved the protection of the most volatile active compounds from fast evaporation. Likewise, cyclodextrin units enhanced the preservation of antioxidant activity, but the weak scavenging potential of E. globulus essential oils was the limiting factor. In this sense, promising results were obtained by replacing said essential oil with hydroxytyrosol.

Phenomenological continuous digester models are normally limited to axial flow. However, under industrial conditions, liquor also flows radially in extraction zones. While multidimensional expansion using computation fluid dynamics is possible, the increase in mathematically complexity and computation burden is intractable for online control and optimization. In this work, an approximate algebraic flow model is proposed which removes the need to evaluate momentum continuity. The model, based on streamlines, superimposes radial and axial flow profiles. The dynamic response, when compared against a single continuous stirred tank model, was found to better predict the process response during industrial trials. Simulation studies suggest enhanced lignin removal and variability reductions are possible by increasing recirculated liquor flow rates in the zone, a result of flattening the radial chemical and temperature profiles in the chip phase. However, a minimum occurs as chemical and energy losses in the extracted flow leaving the zone take precedence.

Thermo-mechanical Pulping (TMP) is one of the most energy-intensive industries where most of the electrical energy is consumed in the refining process. This paper proposes the energy-saving refining optimization strategy by integrating the machine learning algorithm and heuristic optimization method. First, refining specific energy consumption (RSEC) and pulp quality identification models are developed using Artificial Neural Networks. In the second step, the developed identification models are incorporated with the Genetic algorithm to minimize the total refining specific energy consumption while maintaining the same pulp quality. Simulation results prove that a deep multilayer perceptron neural network is a powerful tool for creating refining energy and quality identification models with the model correlation coefficients of 0.97, 0.94, 0.92, and 0.67 for the first-stage RSEC, second-stage RSEC, final pulp fiber length, and freeness prediction, respectively. Findings confirm that the average total RSEC reduction of 14 % is achievable by utilizing the proposed optimization method.

Currently, there are two procedures to determine the basis weight in papermaking processes: the measurements made by the quality control laboratory or the measurements made by the quality control system. This research presents an alternative to estimating basis weight-based artificial neural network (ANN) modeling. The NN architecture was constructed by trial and error, obtaining the best results using two hidden layers with 48 and 12 neurons, respectively, in addition to the input and output layers. Mean absolute error and mean absolute percentage error was used for the loss and metric functions, respectively. Python was used in the training, validation, and testing process. The results indicate that the model can reasonably determine the basis weight given the independent variables analyzed here. The R 2 {R^{2}} reached by the model was 94 %, and MAE was 12.40 grams/m 2 . Using the same dataset, the fine tree regression model showed an R 2 {R^{2}} of 99 % and an MAE of 3.35 grams/m 2 . Additionally, a dataset not included in the building process was used to validate the method’s performance. The results showed that ANN-based modeling has a higher predictive capability than the regression tree model. Therefore, this model was embedded in a graphic user interface that was developed in Python.

Fillers are the second major component of paper, and can give certain properties to paper-based materials. However, if we want to use fillers to develop novel functional paper-based materials, some challenges have to be considered such as filler functionality, retention rate, and the negative effects. To meet with these challenges, the present work proposed a fabrication concept of bio-based composite fillers. The concept combined the crystallization of target component and the gelation process of chitosan (CS), simultaneously. The gels carried and protected the crystals, and served as bridge between crystal of fillers and the paper matrix. To explore and demonstrate the concept, CaCO 3 /CS bio-based composites were successfully fabricated. The composite fillers were further optimized to be suitable for paper-making. The fabrication concept could significantly increase the filler retention rate (up to 90.57 %), the filler bondability (increased over 10 times) and the mechanical strength (59.7 % higher than paper without fillers). The fabrication concept was also applicable to functional materials. Zeolitic imidazolate framework-8 (ZIF-8)/CS composite fillers were successfully fabricated, and endowed the resulted paper with high surface area (180 times higher than pure cellulose paper). This fabrication concept would be useful to develop functional paper-based materials in the future.

In this article, the chain scission kinetics of cellulose in acid bamboo paper aging were studied and further applied to evaluate the lifespan of acid bamboo paper. In combination with analytical theory and Monte-Carlo simulations, the ideal random scission mechanism of cellulose macromolecules with arbitrary molecular weight distribution (MWD) was studied first. The molecular weight distribution evolutions obtained by the two methods were in good agreement, indicating the feasibility of the Monte-Carlo algorithm. Furthermore, the relationship between the ideal random scission mechanism and real paper aging was studied in an accelerated aging experiment at 105 °C. The Monte-Carlo algorithm could basically reproduce the MWD of accelerated aging at various degradation degrees, indicating that the ideal random scission mechanism is predominant in bamboo paper aging. Therefore, the relevant kinetic model can be applied to lifespan evaluation. In three other aging experiments, the activation energy of paper aging was determined by the Arrhenius equation, which facilitated the calculation of the rate constant of paper aging at room temperature. It is expected that bamboo paper can be preserved for more than a thousand years.

Given the competitiveness in the tissue paper market, manufacturers are continuously seeking eco-friendly options to improve its properties. This work highlights the incorporation in tissue paper of fibrous formulations of deoxyribonucleic acid (DNA), taking advantage of the extremely versatile functionality of this macromolecule, which is, besides biodegradable and obviously biobased, safe for human health. Blends of pulps and salmon DNA were characterized through thermogravimetric analysis, scanning electron morphology, water absorptivity and desorption rate monitoring. It was found that water uptake increased by +43 % for a 1:9 DNA/pulp blend. Then, the presence of DNA accelerated water release. Moreover, DNA was used to produce laboratory tissue paper sheets in two ways: from said blends and by direct addition to the pulp slurry. Each method had a different effect on paper properties, the most promising result being for pre-blending, by which the tensile index increases from 7 to 9 N·m·g –1 . Although it was not possible to improve every desirable property, this was not detrimental to softness or water absorptivity. In conclusion, DNA showed potential as a dry strength additive not only for tissue paper, but also for food wrapping or for any other application that could benefit from biocompatibility.

Paper is the most successful recycled material from commercial and municipal wastes. Part of recycled paper requires deinking to meet the product requirement, such as tissue, printing grade and newspaper. The original print method plays a major role in deinking performance. The digital print methods, such as electrophotographic (or laser) print, have been rapidly adapted in the commercial printing. Paper mills need to modify their procedure to deink these types of recycled paper, which contain fine toner particles. In this study, the recyclability of electrophotographic printed paper has been evaluated extensively, or three repeats with an industrial standard. Meanwhile, recycled fiber from each repeat underwent printability analysis. Except the influence from papermaking method and pulp furnish, the strength of the recycled fiber slightly declines after each repeat because of fiber deterioration, which also affected the paper surface properties. However, the recycled fiber presented good printability on each recycling, especially on print density and fine details. It suggested that the electrophotographic substrate can tolerate a high recycled fiber content.

Sugars are a sustainable platform for producing chemicals and polymers, while cellulose nanofibers (CNF) are sustainable materials with high specific mechanical properties that have an important role to play in many applications. This study highlights the feasibility of producing sugars and CNF using high dry matter (DM) content of 20 %. A commercial enzyme cocktail at low dosage, 5 mg EP/g DM, and a high 15 mg EP/g DM, were used to hydrolyze the pulp cellulose to produce sugars and CNF. HPLC was used to evaluate the cellulose conversion rate and amount of sugar realized. The CNF were studied using TEM, the diameter of the CNF were measured and estimate the crystallinity. The cellulose conversion plateaued at about 48 h for both the low and high dosage, indicating inhibition due to higher sugar concentration and/or increased recalcitrance of the remaining CNF. The CNF obtained at low enzyme indicated the fibrils were insufficiently separated. At the high dosage, less clumps were observed and with smaller diameter than with the low enzyme dosage. The high dosage also produced CNF with significantly higher crystallinity index, confirming that amorphous cellulose portions readily underwent enzymatic hydrolysis and left more recalcitrant CNF.

In this study, two methods were used to extract fibers from industrial corncob residue. The extracted fibers were compared with different characterization methods such as Zeta potential, FAS-VII fiber analysis system, GPC and XRD. The average length and width of the fibers treated by NaOH/H 2 O 2 were 80 µm and 10 µm. The molecular weight was 17653, and the crystallinity was 49.9 %. Correspondingly, the average length and width of fibers treated with CH 3 COOH/NaClO 2 were 100 μm and 10 µm. The molecular weight was 18810, and the crystallinity was 61.9 %. Then, they were modified to prepare carboxymethyl cellulose, which was used to improve the physical properties of paper, the result indicated that both of the carboxymethyl cellulose had good effect. Under optimal experimental conditions, the folding endurance, tensile index, burst index of the handsheets were increased by 37.38 %, 28.78 %, and 28.8 %, respectively. SEM results showed that the addition of carboxymethyl cellulose made the fibers stick closely, which improving the paper properties.

In today’s world where natural resources are rapidly decreasing, recycling printed papers, and their use in paper production will reduce the environmental pollution caused by waste paper. Thus, energy savings can be achieved with less energy consumption. Although many methods are used in the deinking of printed papers, the effectiveness of these methods varies depending on many parameters, such as the type of paper to be de-inked, the type of printed ink in the printing system, and the chemicals used in deinking. In this study, the effect of pH in the deinking process was studied. Electrophotographic printed papers were used as the printed paper in this study, and the INGEDE method was applied as the deinking method. In this method, 3 different pH environments were prepared and an ink removal process was carried out in this environment. Optical and physical properties were determined by producing hand-sheet papers from the deinked pulp. In addition, test prints were made to determine the printability of the produced hand-sheet papers in the electrophotographic printing system.

The characteristics of cellulose micro/nanofibrils (MFC/CNF) can be improved with pre-treatments of the original fibers. The present work is proposed to study pre-treatment with sodium silicate (Na 2 SiO 3 ) on bleached fibers of Eucalyptus sp. (EUC) and Pinus sp. (PIN) and its effects on the quality index of MFC/CNF. Particle homogeneity, turbidity, and microstructure of the suspensions were evaluated. Similarly, the physical-mechanical, and barrier properties of the films were studied. With the results obtained for suspensions and films, the quality index (QI) was MFC/CNF calculated. The smallest particle dimension was observed for MFC/CNF of Pinus sp. with 10 % of Na 2 SiO 3 , as well as the lowest turbidity (∼350 NTU) was obtained for MFC/CNF of Pinus sp . with 5 % of Na 2 SiO 3 . The pre-treatments reduced the transparency of the films by ∼25 % for EUC and ∼20 % for PIN. The films presented a suitable barrier to UVC radiation, water vapor, and oil. The tensile strength of EUC and PIN films was increased by 20 % using 10 % of Na 2 SiO 3 . The same concentration of Na 2 SiO 3 provided QI 70 for EUC MFC/CNF. The Na 2 SiO 3 was efficient to obtain the MFC/CNF with interesting properties and suitable to generate films with parameters required for packaging.