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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. [ABSTRACT FROM AUTHOR]

Pressure to increase the renewable energy matrix motivates the search for new energy sources. Pulp and paper mills have been constantly expanding in Brazil, and to ensure their competitiveness, new processes should be established both in terms of reducing the waste discarded in landfills, as well as the substitution of fossil fuels used in the mills. The present work aims to evaluate the energy potential of primary sludge (PS), secondary sludge (SS), a mixture of primary and secondary sludge (MS) and tree bark (B) generated in a Brazilian TMP mill. Characterization of all biomasses was performed. Moisture content, higher, lower, and net heating value, elemental, structural, and immediate composition, thermogravimetric analysis and quantification of minerals and metals were determined The bark presented the highest higher heating value (HHV) (18.90 MJ kg−1), while the secondary sludge had the lowest HHV (12.45 MJ kg−1). The high concentration of ash in the sludges PS (26.58%), SS (40.46%) and MS (25.78%) negatively affected their heating value. The sludges also showed high moisture content, which made their burning without a previous drying stage unattractive. Nevertheless, the sludges and the bark are rich in carbon which makes them attractive for use as biomasses for energy generation. [ABSTRACT FROM AUTHOR]

Delignification and fractional pretreatments are essential for valorization of wood biomass in various bioproducts. Herein, lignocellulose wood fibers were exposed to a eutectic mixture (EM) of carvacrol and methanesulfonic acid for different times. The resulting structural and chemical alterations in biomass were explored in terms of the fiber morphology and fractional chemical composition through fiber image analysis, field-emission scanning electron microscopy, high-performance liquid chromatography, and a novel approach based on fluorescence-lifetime imaging microscopy (FLIM). The autofluorescence of the lignocellulose fibers, which was primarily due to lignin with contributions from cellulose and hemicellulose, enabled application of FLIM in lignocellulose compositional analysis in micro-scale. FLIM analysis revealed that EM treatment efficiently removed lignin from the outer fiber layers. Furthermore, the effective EM treatment time was 3 h (with a residual lignin content of ~ 7 wt%), after which defects were observed on the fibers and the cellulose chains started breaking. This degradation was also indicated by a shift of the lifetime spectra toward the fluorescence lifetime of cellulose with increasing treatment time. Overall, our findings provide valuable insights to the response of lignocellulose fibers to EM treatment, contributing to the important goal of wood biomass application in bioproducts. [ABSTRACT FROM AUTHOR]

Alkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP‐TMP‐AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) bleaching in ethanol-water media was used to improve the bleaching efficiency of the chemi-thermomechanical pulp (CTMP). The brightness of CTMP increased and the yellowness decreased when the ethanol ratio was increased to 50%. However, when more than 50% ethanol was added, the brightness decreased, and the yellowness increased. In general, H2O2 bleaching in ethanol-water media, except for 100% ethanol, improved the optical properties of CTMP compared to conventional H2O2 bleaching. Moreover, the chemical composition of CTMP did not alter significantly. The best bleaching condition for CTMP was observed in 50% ethanol at a bleaching temperature and time of 80 °C and 120 min, respectively. The brightness of CTMP under this condition increased by approximately 22% compared with conventional H2O2 bleached CTMP. Principal component analysis (PCA) revealed that the optical properties of bleached CTMP were affected by the structural changes of the aromatic ring and carbonyl group in lignin and carbonyl group in hemicellulose. Consequently, the specific optimal ratio of ethanol that could improve the optical properties of CTMP was determined. The results can serve as a reference for fabricating improved CTMP for its practical application in high-grade papermaking.

Previously it was shown that wood chip compression or enzyme impregnation prior to refining reduces energy consumption and improves pulp quality. This work characterizes the effect of different magnitudes and rates of compression on the extent of enzymatic hydrolysis. A laboratory compressor and a controlled uniaxial load set-up were used to apply different compression ratios and compression times to mixed-softwood wood chips. The chips were subsequently subjected to enzymatic hydrolysis with a high-yield exoglucanase preparation to demonstrate changes in cellulose hydrolysis. Enzymatic hydrolysis yield increased with compression ratio but was unaffected by compression time. Increasing compression ratio increased removal of soluble molecules such as sugars and acid-soluble lignin. Microscopy imaging showed increased cell wall buckling and fracturing with increased compression. The morphological changes led to improved enzyme diffusion and resulted in higher available surface area. The improved cellulose hydrolysis is due to changes in wood morphology as well as the removal of extractives. [ABSTRACT FROM AUTHOR]

A more efficient application of a dry strength agent (DSA) was investigated to improve the strength of thermomechanical pulp (TMP) blended paper. Strength improvement by DSA application was more effective for hardwood bleached kraft pulp (Hw-BKP) than TMP. The degree of strength improvement of DSA further increased with the increasing degree of refining of Hw-BKP. The strength of the paper was decreased by the fines fractionation of TMP, but the strength improvement efficiency of DSA for the fines fractionated TMP increased. In order to increase the strength of TMP mixed paper using DSA, it is expected that DSA should be adsorbed only to Hw-BKP with high strength improvement efficiency, not TMP fines. When the DSA was mixed with Hw-BKP before contact with other stocks, it was confirmed that the effect of improving the strength by the DSA is the best. The strength improving effect increased as TMP fines were removed. Therefore, to improve the strength of the paper containing TMP in Hw-BKP by adding a DSA, it is preferable to selective apply the DSA to Hw-BKP while blending only the fibers of TMP by fractionation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile, scalable production of hyperbranched wood fiber using mild disc milling. • Air dried foam assembled from hyperbranched wood fiber with no binder use. • Sub-fibrous structures of wood fiber improved foam's mechanical properties. • Natural, high melting point wax allowed enhanced water/moisture repellency. • Woody foam demonstrated better thermal insulation than commercial glass fiber mat. Demand for sustainable building thermal regulation is driving the development of low carbon-intensive, renewable, and safe-to-use materials to substitute the dominant synthetic polymers and inorganic mats. This study proposes a novel mild mechanical pretreatment strategy to fabricate high-performance, self-strengthening thermal insulation board in a low cost and scalable approach from chemi-thermomechanical pulp (CTMP), a type of high-yield wood pulp. CTMP fibers, after subject to a short period of disc milling, were found to gain abundant sub-fibrous structures at multiple scales. After foaming and air-drying, such micro-fibrillated fibers (MF-CTMP) formed robust, binder-free foam under capillary force with remarkedly stronger physical entanglement between fibers compared to that of pristine CTMP, achieving 3.7 folds Young's modulus, 2.9 folds ultimate stress, and 1.9 folds toughness with respect to the latter. Palm wax coating further provided a sustainable hydrophobic protection for the foam (contact angle of ∼ 110°). The high porosity and structural tortuosity endowed the hydrophobic MF-CTMP foam with excellent thermal insulation property (thermal conductivity of 33.1 ± 2.3 mW/(m∙K)), demonstrating significantly better performance than a commercial glass fiber thermal insulator. Compared to other lignocellulosic boards prepared using freeze-drying or supercritical drying operations, the hydrophobic MF-CTMP foam represents a novel low cost, binder-free, and scalable technology for commercial sustainable thermal insulation applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Molten oxalic acid dihydrate can convert thermomechanical pulp into LCNCs in 30 min. • Over 70 % yield of LCNC with uniform dimension can be achieved through OAD hydrolysis process. • The process represents high retention of cellulose (93 %) and lignin (97 %). • OAD can be recycled by recrystallization with retained high hydrolytic power. • Chemical recycling can substantially reduce environmental impacts verified by LCA. Nanocellulose is of growing interest due to its great potential in many value-added applications and its unique characteristics. However, conventional methods for nanocellulose isolation are challenged by various economic and environmental concerns. With the use of recyclable oxalic acid dihydrate (OAD), this study demonstrated the rapid, high-yield production of lignin-containing cellulose nanocrystals (LCNCs) from thermomechanical pulp (TMP). Serving as the sole solvent and reactant, molten OAD effectively hydrolyzed TMP within 30 min at 110 °C, leading to complete removal of hemicellulose (97 %) but retaining most of the cellulose (93 %) and lignin (97 %). This modified TMP can be converted into LCNCs with a high overall yield of >70 % via microfluidization. The LCNCs possessed satisfactory thermal stability and exhibited a nanoscale morphology of highly uniform cellulose nanocrystals (7.0 nm in width, 3.9 nm in height, 200–300 nm in length, and 72 % in crystallinity), randomly implanted by lignin aggregates. The unreacted OAD could also be readily recycled via crystallization from the post-hydrolysis mixture. The recycled OAD showed good performance retention for at least 4 cycles, indicating its suitability for continuous TMP hydrolysis. Further life cycle assessment suggested that the recycling potential could reduce the global warming potential and energy use by 48 % and 47 %, respectively. Overall, it was apparent that recycling molten OAD provided a promising approach to rapidly make clean, high-yield LCNCs with low energy use and improved reagent utilization. [ABSTRACT FROM AUTHOR]