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Pulp Bleaching Today
This book describes the most effective application of chemicals in bleaching.It starts with a brief overview of the history of bleaching and then focuses on recent developments.The ban of chlorine from bleaching pulp has shifted bleaching to environmentally sound procedures.
eBook
Single fiber swelling behavior for natural and man-made cellulose fibers under alkaline treatment
Swelling behavior of cotton, dissolving wood pulp (DWP), viscose staple fiber, and Tencel staple fiber in varying sodium hydroxide (NaOH) concentration were investigated by means of optical microscopy and were characterized by molecular mass distribution, X-ray diffractometer, and dynamic vapor sorption. The effect of temperature (20–45 °C) and duration (0–120 min) was studied. The results reveal that the swelling ratio of fiber in alkali solution depends on fiber accessibility and NaOH concentration. Viscose staple fiber exhibited the highest swelling ratio and lowest swelling ratio observed for dissolving wood pulp fiber among all the materials. The cotton or DWP fibers provide maximum swelling during alkaline steeping (18wt % lye) at higher temperatures, i.e., 45 °C. As for viscose staple fiber and Tencel staple fiber, using 12 wt% lye concentration and steeping at lower temperatures, i.e., 20 °C maximum swelling behavior.
Journal Article
Toward eco-friendly menstrual products: a comparative life cycle assessment of sanitary pads made from bamboo pulp vs. a conventional one
The predominant menstrual products utilized by women are sanitary pads. The majority of disposable sanitary pads are comprised of plastics and bleached wood pulp, often accounting for as much as 90% of their composition by weight. Nevertheless, the overall environmental footprint of production to disposal of disposable sanitary pads is often overlooked due to the cultural stigma associated with menstruation and the lack of chemical information. This study aims to evaluate the potential environmental impact of the life cycle of sanitary pads and provide insights for decision-making and driving improvements in product design and production processes. It is important to note that this study does not aim to assess the health and safety of the products for consumer use. A case study was conducted at Hempur in Stockholm, Sweden, to assess the environmental impacts of a disposable pad made from bamboo pulp and polylactic plastic. The study applied life cycle assessment to compare the life cycle of Hempur disposable sanitary pads with conventional ones made of polymers and bleached wood pulp. The research findings reveal that Hempur sanitary pads made from plant-based materials have lower adverse environmental impacts than the conventional ones considered in the study. The upstream operations of Hempur sanitary pads were identified as the least environmentally friendly phase of the product due to the use of unbleached wood pulp and polylactic plastic, which together account for between 40 and 80% in every impact category, most notably water scarcity and abiotic element depletion. Hempur can improve its environmental performance by switching from coal to hydropower for electricity generation in bamboo pulp manufacturing, leading to a decrease in global warming and acidification. Finally, we recommend alternatives for PLA, and the use of bamboo in the core part of the Hempur sanitary pad should be considered and assessed.
Graphical Abstract
Journal Article
A method for chemical and physical modification of oriented pulp fibre sheets
Wood pulp fibres are promising reinforcements for biocomposites due to their renewable resource origin and mechanical properties. An oriented and dense fibre reinforcement structure is beneficial for biocomposite properties. We present a method of modifying fibres (e.g. to increase strain to failure) in pre-formed oriented high-density paper structures intended for biocomposites or as hot-pressed fibre materials. Mildly delignified, well-preserved holocellulose fibres from softwood are used. Cold alkali treatment (hemicellulose removal) and mercerisation (conversion to cellulose II) were carried out successfully on oriented fibre sheets. Controlled anisotropy and sheet density are achieved from untreated and straight fibres in the sheet formation step. High mechanical properties and increased ductility of mercerised sheets were observed, which may be valuable for hot-pressed fibre materials (E ≈ 7.1 GPa, strength of 108 MPa and strain to failure of 5.3%) and biocomposites. In contrast, modified wood pulp fibres were difficult to orient, resulting in higher sheet porosity and weak interfibre bonding.
Graphical abstract
Journal Article
Enhanced energy savings in enzymatic refining of hardwood and softwood pulp
Background
Pulp refining is an energy consuming, but integral part of paper production with the aim to increase tensile strength and smoothness of paper sheets. Commercial enzyme formulations are used to lower the energy requirements by pre-treatment of pulp before refining. However, a high number of different commercial enzyme products are available on the market containing enzymes of varying origin and composition, which complicates the prediction of their behavior, especially using different pulp types.
Results
Endoglucanase-rich enzyme formulations were characterized regarding enzyme activity at different temperatures, resulting in a significant decrease of activity above 70 °C. Some enzyme preparations additionally contained arabinosidase, xylanase and β-glucosidase activity consequently resulting in a release of xylose and glucose from pulp as determined by high-performance liquid chromatography. Interestingly, one enzyme formulation even showed lytic polysaccharide monooxygenase (LPMO) activity of 3.05 nkat mg
−1
. A correlation between enzyme activity using the endoglucanase specific derivatized cellopentaose (CellG5) substrate and enzyme performance in laboratory PFI (Papirindustriens forskningsinstitut) refining trials was observed on softwood pulp resulting in a maximum increase in the degree of refining values from 27.7°SR to 32.7°SR. When added to a purified endoglucanase enzyme (31.6°SR), synergistic effects were found for cellobiohydrolase II (34.7°SR) or β-glucosidase enzymes (35.7°SR) in laboratory refining. Comparison with previously obtained laboratory refining results on hardwood pulp allowed differences in enzyme performance based on varying pulp types to be elucidated.
Conclusions
Interestingly, the individual enzymes indeed showed different refining effects on softwood and hardwood pulp. This difference could be predicted after development of an adapted enzyme activity assay by combination of the derivatized cellopentaose CellG5 substrate with either softwood or hardwood sulfate pulp.
Journal Article
Study on the Effects of Technology Parameters on the Water Absorption and the Thickness Swelling of the Pressed Bamboo Pulp Plywood
The application of bamboo by-products such as bamboo branches, chips to recycle and produce pressed bamboo pulp is an urgent task in Vietnam. It perfectly replaces natural wood with artificial wood embryos from bamboo powder, which has both economic benefits of reserving the source of raw materials, environmental protection... The paper presents a study of the influence of technological parameters on the water absorption and swelling thickness of pressed bamboo pulp plywood in order to ameliorate the quality of pressed bamboo pulp plywood in production of new materials for civil engineering with environmentally friendly bamboo wood pulp materials.
Journal Article
The Effect of Cellulose Nanofibres on Dewatering during Wet-Forming and the Mechanical Properties of Thermoformed Specimens Made of Thermomechanical and Kraft Pulps
Due to environmental concerns regarding single-use plastic materials, major efforts are being made to develop new material concepts based on biodegradable and renewable resources, e.g., wood pulp. In this study, we assessed two types of wood pulp fibres, i.e., thermomechanical pulp (TMP) and Kraft pulp fibres, and tested the performance of the fibres in wet-moulding and thermopressing trials. Kraft pulp fibres appeared to retain more water than TMP, increasing the dewatering time during wet-moulding and apparently increasing the compression resistance of the pulp during thermoforming. Additionally, cellulose nanofibres (CNF) were added to the pulps, which improved the mechanical properties of the final thermopressed specimens. However, the addition of CNF to the pulps (from 2 to 6%) had a further decrease in the dewatering efficiency in the wet-moulding process, and this effect was more pronounced in the Kraft pulp specimens. The mechanical performance of the thermoformed specimens was in the same range as the plastic materials that are conventionally used in food packaging, i.e., modulus 0.6–1.2 GPa, strength 49 MPa and elongation 6–9%. Finally, this study demonstrates the potential of wood pulps to form three-dimensional thermoformed products.
Journal Article
Characterization of the supermolecular structure of cellulose in wood pulp fibres
The hierarchic organization of cellulose fibrils (microfibrils) was investigated in holocellulose, sulphite pulp and kraft pulp using TEM, XRD, ED and FTIR. There were remarkable differences in both the fibril structure and fibril aggregation between the samples. TEM observations revealed more intimately associated fibrils in the kraft pulp compared to the sulphite pulp and the holocellulose, results in agreement with previous CP/MAS 13C-NMR data [Hult E.-L. et al. (2002) Holzforschung 56: 231–234]. Furthermore, the cellulose crystallinity was higher in the kraft pulp sample. With respect to the cellulose Iα and Iβ allomorphs, these samples were controversial when different analytical techniques were applied. Due to the small fibril size and the low degree of order of cellulose in these samples, the concept of crystalline triclinic and monoclinic components as determined by diffraction analysis may not be adequate. Instead the fibril can be regarded to have different degrees of lateral order (including paracrystalline ordering) that can be reoriented to Iβ type conformation and packing upon pulping.
Journal Article
Using Siberian fir (Abies sibirica) dead wood in wood fiberboard production
This paper considers the possibility of using Siberian fir (Abies sibirica) wood damaged by Polygraphus proximus Blandford after various periods of its death (up to 19 years) as raw material to produce fiberboard. Damaged wood was mechanically processed into chips of various dimensions as per GOST 15815(1983). The produced chips were used to prepare wood fiber pulp using thermomechanical methods and two stages of grinding with approximately the same conditions as those used to produce wet fiberboard. Fiber refining was performed using fibrillating refiner discs with all other conditions being equal. The paper considered the changes in quality indicators and fractional composition of fibers during the preparation of wood fiber pulp after different periods of wood death, as well as physical and mechanical properties of produced boards. The obtained research results may indicate the possibility of effectively using damaged Siberian fir wood after different periods of its death as raw material to produce fiberboards, while providing physical and mechanical properties of products (density 960 to 1070 kg/m3, static bending strength 36 to 44 MPa, internal bonding 0.51 to 0.7 MPa, modulus of elasticity 3880 to 4750 MPa, deflection 2.7 to 3.6 mm) that comply with GOST 4598-2018 (EN 622-2), while not requiring binding resins.
Journal Article