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Copyright © The Author(s) 2022. This paper develops a novel paper additive for effectively recycling old corrugated container (OCC) by functionalizing nanocellulose (NC) with diethylenetriaminepentaacetic acid (DTPA) and chitosan (CS), and investigate the reinforcing mechanisms and effect of the developed additive on the physical properties of recycled OCC pulp handsheets. The tensile, tear and burst index, air permeability, tensile energy absorption (TEA), and drainage performance of the recycled OCC handsheets are examined. Fourier transform infrared FTIR) spectroscopy, thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM) are used for the chemical and microstructure characterization of both NC based additives and paper from recycled OCC pulp. The results show that functional groups on the NC based additive, such as carboxyl, amino and hydroxyl groups, can bond with the hydroxyl groups on the recycled OCC fibres to generate a chemical bond. This leads to an increase in the crosslinks and bonding area between the fibres, which increases their tensile strength and improves their recycling rate. SEM shows that the paper with NC based additives had tighter inter-fibre bonds and smaller paper pore structure. Addition of 0.3% NC-DTPA-CS additive results in optimal properties of the recycled OCC paper with an increase by 31.64%, 22.28% and 36.6% of tensile index, tear index, burst index respectively, and the air permeability decreases by 36.92%. National Natural Science Foundation of China [Grant number 31971592]; the National Key Scientific Research Project of China [Grant number 2016YFD060070504].

This paper presents a binary reinforcement system of polyamide polyamine epichlorohydrin with nanocellulose (PAE-NC) for effectively modification of the reclaimed fibres for paper production, and based on the improvement of physical and mechanical properties of cellulosic fibres together with PAE-NC self-crosslinking networks, the strengthening mechanisms of recycled papers are examined. The PAE-NC binary system was applied directly to old corrugated container (OCC) and softwood bleached kraft pulp (SWBKP), and handsheets are prepared with varying amounts of PAE/NC/PAE-NC, namely 0.05, 0.1, 0.3, 0.5, 0.75, 1.0, 1.5, 2.0 wt% (dry pulp). The results showed that the studied additives improved the performance of recycled fibres, whether SWBKP or OCC pulp, and handsheets in solely or combined mechanisms except for the air permeability of the handsheets. The treatment of PAE-NC combination was significantly more effective than those of PAE or NC alone for both OCC and SWBKP, although the combined PAE-NC treatment results in better performance enhancement for OCC than SWBKP handsheets, and the NC alone is more effective than PAE for SWBKP recycled paper and conversely for OCC recycled paper. SEM observations further confirmed that the combined PAE-NC addition treatment imparted a relatively uniform surface structure to the handsheet.

The rapid economic growth and environmental concerns have led to high demands on paper and paper-based products in terms of variety, quantity, quality, and specialty. Enhancement and functionalization with additives are constantly required. Moving away from traditional petroleum-based additives, researchers have attempted to use “green” nanoadditives by introducing renewable environmentally friendly nanocellulose. This article studies the functions of nanocellulose as bio-additives (enhancer, retention and filtration reagent, and coating aid) in paper and paper products, and overviews the research development of nanocellulose-based additives and their applications in the paper industry for both efficient production and paper functionalization. The review shows that (1) a variety of nanocellulose-based bioadditives have been reported for various applications in paper and paper-based products, while commercially viable developments are to be advanced; (2) nanocellulose was mostly formulated with other polymer and particles as additives to achieve their synergistic effects; (3) major interests have concentrated on the nanocellulose in the specialty papers as representing more value added products and in the efficient utilization of recycled fibers, which remains most attractive and promising for future development. This report shall provide most useful database information for researchers and industries for paper recycling and enhancement, and paper-based products innovation and application.

With rising interior air pollution, health, and food shortage concerns, wood adhesives derived from non-food sustainable materials have therefore attracted considerable attention. Here we developed an eco-friendly cottonseed-lignin adhesive consisting of non-food defatted cottonseed flour (DCF), alkali lignin (AL), and graphene oxide (GO). The cation-π interaction, and hydrogen and covalent bonds between AL@GO and DCF collectively enhanced the cross-linking structure of the cured cottonseed-lignin adhesive, based on the Fourier-transform infrared spectroscopy, thermogravimetric analyses, scanning electron microscopy, and sol-gel tests. The high performance of the developed cottonseed-lignin adhesive was evidenced by its increased wet/dry shear strength and decreased rheological properties before curing and improved thermal stability and decreased soluble substances after curing. Particularly, the highest wet shear strength of poplar plywood bonded with cottonseed-lignin adhesive was 1.08 MPa, which increased by 74.2 and 54.3% as compared to the control and requirement of the Chinese standard GB/T 9846-2015 for interior plywood (≥0.7 MPa), respectively. The technology and resultant adhesives showed great potential in the preparation of green woody composites for many applications.

This paper is to develop a novel paper additive for effectively recycling old corrugated container (OCC) by functionalizing nanocellulose (NC) with diethylenetriaminepentaacetic acid (DTPA) and chitosan (CS), and investigate the reinforcing mechanisms and effect of the developed additive on the physical properties of recycled OCC pulp handsheets. The tensile, tear and bursting strength, whiteness, air permeability, tensile energy absorption of the recycled OCC handsheets are examined. Fourier transform infrared FTIR) spectroscopy, thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM) are used for the chemical and microstructure characterization of both NC based additives and recycled OCC pulp paper. The results show that the functional groups, such as carboxyl, amino and hydroxyl groups on the NC based additives, can combine with the hydroxyl groups on the recycled OCC fibres to generate chemical bonds, which increase the crosslinks between fibres as well as the bonding area, thus enhancing their tensile strength and improving their recycling rate. SEM shows that the paper with NC based additives had tighter inter-fibre bonds and smaller paper pore structure. Addition of 0.2% NC-DTPA-CS additive results in optimal properties of the recycled OCC paper with an increase by 32%, 188%, 19% and 35% of tensile strength, tearing degree, breaking resistance and air permeability respectively.

This study reports on the preparation and application of bio-based adhesive derived from renewable defatted soy flour (DSF) and epichlorohydrin (ECH), aiming at substituting formaldehyde-based adhesives in the wood industry. DSF was treated with Viscozyme® L to hydrolyze plant cell wall carbohydrates and then adjusted to an extremely low pH with hydrochloric acid containing ferric chloride to unfold the tertiary and/or quaternary structure of soy protein and expose its functional groups. The treated DSF was then glycidized with ECH to obtain the bio-based adhesive. The resulting adhesive contained epoxy groups, which were evidenced by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and 1H nuclear magnetic resonance. After curing, the epoxy groups contributed to good thermal stability and gluability of the adhesive. The grafting ratio of ECH decreased by 37.8% as the mass fraction added was increased from 5 to 25%, whereas the viscosity increased sharply by 2889.5% and the solid content increased slowly by 10.5%. Wet shear strength of Pinus massoniana plywood bonded with the bio-based adhesive with an ECH mass fraction of > 10% of the DSF mass was higher than 0.93 MPa, which met the requirements of the Chinese National Standard for plywood for interior/exterior applications. These results support the use of soy flour-based adhesives for plywood and provide data for evaluating their use as sustainable materials for other applications.

The mesoporous aluminosilicate synergy with Cu B P anti-mildew agent was studied with the objective of improving the mildew resistance of bamboo scrimber. The Si Al inorganic film with enormous pore volume, was added to cover on the bamboo fiber's surface by a simple and sustainable dip-coating process. The results showed that the process decreased the leachability of the anti-mildew agents, which would improve efficiency of preservative agents and extend service life for the bamboo-based products. The average mold control effectiveness of three types of mold and stain fungi of the final product was greatly improved with 91.75% in optimized samples. In addition, the outdoor test indicated that the anti-mildew agents worked satisfactorily and no evidence of microbes infection and stain was found in bamboo scrimbers prepared by optimum processing parameters.

Chinese fir bark was selected as a precursor, and a chemical activation method was used to prepare high surface area activated biocarbon materials with heteroatom doping. The impacts of the activation temperature on pore structure and chemical characteristics were studied. Activated biocarbon electrodes with heteroatoms of N (1.00–1.60%) and O (3.60–12.87%) were then fabricated for electrochemical performance analysis, and the relationships among the pore structure, chemical characters and specific capacitance were discussed. The results show that the specific capacitance of activated carbon electrodes from both the cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) tests obviously increased with increasing activation temperature in the range of 500 °C to 700 °C. The electrode fabricated with the activated carbon prepared at 700 °C exhibited the highest specific capacitance of 320 F/g at a scan rate of 2 mV/S by CV test and 342 F/g at a current density of 0.5 A/g by GCD test, which is comparable to or higher than that of most carbon-based capacitors. The favorable electrochemical performance may be attributed to the synergistic effect of the hierarchically suitable porous structure and dual doping of nitrogen and oxygen heteroatoms.

This paper addresses a circular economy strategy for the medium density fiberboard (MDF) industry by effectively recycling fibers from MDF residues as raw materials, additionally reducing waste discharge, preserving the ecological environment, saving the wooden resources, and relieving the shortage of raw materials. The work specifically discussed the characteristics and bonding properties of the recycled fibers from the MDF offcuts by the cooking and beating method. The morphology of the recycled fibers was compared with that of the virgin fibers, and then the chemical characteristics of the recycled fibers were analyzed with XPS. Finally, the bonding properties between the recycled fibers and some virgin fibers were compared. The results showed that the fiber length of the recycled fibers is about 12% shorter than that of the virgin fibers and the percentage of shorter fibers (≤0.68 mm) is higher for the former than the latter, in addition, the broken ends ratio of the recycled fibers is 17% higher than that of the virgin fibers, while there is no significant difference in the fiber width and its distribution. SEM and XPS characterizations confirmed that there are some cured UF resin on the surface of the recycled fibers. The MOE, MOR, and IB of the recycled MDF is 5, 10 and 11% respectively lower than those of the fresh MDF manufactured with the virgin fiber, but its TS is 12% lower than that of the fresh MDF, this means that the recycled fiber MDF is more dimensionally stable and water resistant.

This paper presents plasma technology for the functionalization of both carbonized and non-carbonized bamboo surfaces, including bamboo skin, pulp, pith and mixed bamboo groups, for the production of advanced bamboo composites. Oxygen, nitrogen and argon are used as the plasma gas resources, and various plasma powers, gas pressures and treatment times investigated. Surface composition, morphology and wettability of plasma treated bamboos are characterized by using Fourier transform infrared spectroscopy (FTIR) and ESEM to understand the mechanisms of plasma treatment and chemical and physical changes of bamboo surface layer, and interface bond of bamboo composites. Results showed that the efficacy of plasma treatment was bamboo skin > pith > pulp and carbonized > non-carbonized, resulting in different surface characteristics and subsequent interface bonds of bamboo with the optimum plasma parameters being the processing time of 103s, the power of 141W and gas pressure of 38Pa. Oxygen plasma treatment generated an effective surface oxidization and oxygen-containing groups, resulted in significant change in (micro)structure of bamboo surface layer, and led to a significant improvement in the wetteability and interface bonding of bamboo surface and hence physical and mechanical properties of bamboo composites, e.g. MOR of 170 MPa with about 47% increase over untreated bamboo composites. Bamboo composites should be produced with efficacy period of 3 days after plasma treatment for the carbonized and 5 days for non-carbonized bamboo.

In order to solve the practical problem of heat transfer during the hot pressing process of a novel wood-plastic composite plywood, this paper investigates the perforation treatment of polyvinyl chloride (PVC) plastic films and their plywood composites. The PVC films were pretreated by the physical punching method, and the effects of PVC perforation diameter, hot pressing time and hot pressing temperature on the mechanical properties of the plywood composites were investigated by orthogonal experimental design. The results showed that the optimum hot pressing time was 7 min, the hot pressing temperature was 170 °C, and the PVC perforation diameter was 15 mm for the optimum mechanical properties. The punching pretreatment of PVC films gave rise to a reduction of the hot pressing time by 51 s due to improved heat transfer and heat loss by 5.06%, and allowed an increase in the initial moisture content of the veneer by 2–3%, thereby cutting down the drying cost in the veneer production process, which is conducive to energy conservation and environmental protection. Science & Technology Program in Fujian Province of China; Science & Technology Innovation Program in Fujian Agriculture and Forestry University of China

Copyright © 2019 The Author(s). Wood fibers were prepared as core materials for a vacuum insulation panel (VIP) via a dry molding process. The morphology of the wood fibers and the microstructure, pore structure, transmittance, and thermal conductivity of the wood fiber VIP were tested. The results showed that the wood fibers had excellent thermal insulation properties and formed a porous structure by interweaving with one another. The optimum bulk density that led to a low-cost and highly thermally efficient wood fiber VIP was 180 kg/m3 to 200 kg/m3. The bulk density of the wood fiber VIP was 200 kg/m3, with a high porosity of 78%, a fine pore size of 112.8 μm, and a total pore volume of 7.0 cm3·g-1. The initial total thermal conductivity of the wood fiber VIP was 9.4 mW/(m·K) at 25 °C. The thermal conductivity of the VIP increased with increasing ambient temperature. These results were relatively good compared to the thermal insulation performance of current biomass VIPs, so the use of wood fiber as a VIP core material has broad application prospects. Science & Technology Program in Fujian Province of China (2017N3009 ); Science & Technology Innovation Program in Fujian Agriculture and Forestry University of China (CXZX2017375 ).

Wood based composites are widely used in furniture and other building construction, but the majority of which are bonded with formaldehyde-based resins that may cause serious health concern. This study presents an environmentally-friendly soybean based resin via combination of waste newspaper powder (WNP), soybean flour (DSF), and polyamidoamine-epichlorohydrin for woody composites, and its adhesion properties as investigated via shear strength. The results showed that the developed DSF-WNP resin (or soybean based resin) cured well at currently commercial plywood manufacture temperature (130 °C) and could be cured at a lower temperature of 85 °C for energy saving as well, through chemical cross-linking reactions between hydroxyl-azetidinium ring groups in the polyamidoamine-epichlorohydrin and hydrophilic groups, such as amido, carboxyl and hydroxyl in other components. WNP with particle sizes ranging from 120 μm to 250 μm were suitable for the resin applications. WNP resulted in poor dispersion, but lowered water absorption and increased insoluble fraction content and tensile strength in the cured resin. The wet shear strength of plywood bonded with DSF-WNP resin with a 2/5 dry weight ratio of WNP/DSF was 1.24 MPa, which met the requirements of the Chinese National Standard GB/T 9846–2015 for interior plywood. The resin characteristics including fast curing and excellent wet-cohesion performance are comparable to the mostly used urea-formaldehyde adhesives, which showed great potential in wood composites as an alternative to formaldehyde-derived adhesives.

The hybrid composites of polyvinyl alcohol (PVA)/Si–Al were synthesized to improve the thermostability and mechanical properties of ultra-low density fiberboard (ULDF). Their physical and chemical properties were tested by using scanning electron microscopy, Fourier transform infrared spectrometry, X-ray diffractometry, thermogravimetric analysis (TGA), and a microcomputer control electronic universal testing machine. Microstructure results indicated that the distribution of inorganic fillers on the surface of ULDF was improved by the PVA. Analysis of chemical bonds and crystallinity of materials showed that part of the PVA reacted with Si–Al sol, and the other was physically crosslinked in the composite. The thermostability of ULDF decreased with the increasing content of PVA, but the mechanical properties increased. Combined with the TGA and mechanical properties results, a reasonable content of PVA (30%) was obtained. Under this condition, the modulus of rupture, modulus of elasticity, and the internal bond strength of ULDF were 0.35, 24.86, and 0.038 MPa, respectively.

This paper presents the interfacial optimisation of wood plastic composites (WPC) based on recycled wood flour and polyethylene by employing maleated and silane coupling agents. The effect of the incorporation of the coupling agents on the variation of chemical structure of the composites were investigated by Attenuated total reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and Solid state 13C Nuclear Magnetic Resonance spectroscopy (NMR) analyses. The results revealed the chemical reactions that occurred between the coupling agents and raw materials, which thus contributed to the enhancement of compatibility and interfacial adhesion between the constituents of WPC. NMR results also indicated that there existed the transformation of crystalline cellulose to an amorphous state during the coupling agent treatments, reflecting the inferior resonance of crystalline carbohydrates. Fluorescence Microscope (FM) and Scanning Electron Microscope (SEM) analyses showed the improvements of wood particle dispersion and wettability, compatibility of the constituents, and resin penetration, and impregnation of the composites after the coupling agent treatments. The optimised interface of the composites was attributed to interdiffusion, electrostatic adhesion, chemical reactions, and mechanical interlocking bonding mechanisms.