Lignocellulose Nanofibers Research Articles

Interfacial lignin glued cellulose/aramid nanofiber membranes: Combing toughness, stability, and dye rejection performances

Nanoscale cellulose-based membranes have been considered as perfect candidates for organic dye separation attributed to their sustainability, high aspect ratio, and nanoscale designation. However, as natural polysaccharide, nanocellulose still suffers from drawbacks like brittleness and vulnerability. In this work, the tough and stable lignocellulose nanofibers (LCNFs) based composite membranes were fabricated by introducing lignin modified aramid nanofibers (DANFs) as reinforcing agents. Being benefit from the interfacial lignin bridging effects, the noncovalent interactions (e.g., H-bond and π-π stacking) between LCNFs and DANFs strengthened, and the resultant composite membranes presented enhanced tensile strength (∼186.9 MPa, 6.3 time higher than LCNFs membranes), toughness (∼9.28 MJ/m3, 105 time higher than LCNFs membranes), Young’s modulus (∼8.43 GPa, 4.6 time higher than LCNFs membranes), as well as the optimized stabilities (in organic, acidic and alkali conditions). Combing all these advantages, the composite membranes demonstrated promising dye rejection performances toward methyl violet (a reject rate of ∼98.54 % and a flux of ∼29.76 L•m−2•h−1•bar−1), and can removal 63.08 % of methyl violet after 10 recycles. Thus, this research paves a simple and efficient way to made strong LCNFs-based separation membranes that are suitable as dye separator in harsh environments.

The preparation and properties of bamboo lignocellulosic nanofibers based on deep eutectic solvent system

The preparation and properties of bamboo lignocellulosic nanofibers based on deep eutectic solvent system

Cellulose nanofiber aerogels: effect of the composition and the drying method

Highly porous and lightweight aerogels of cellulose nanofibers (CNFs) have emerged as a promising class of material. This study delves into the impact of the composition (lignocellulose nanofibers–LCNFs and CNFs) and the drying methods (supercritical drying and freeze-drying) on the morphology and the properties of nanocellulose-based aerogels. The investigation evaluates the concentrations of nanofibers and the influence of lignin, a constituent of LCNFs recognized for enhancing the rigidity of plant cell walls, on the aerogel’s properties. The shrinkage rates, density, pore structure, and mechanical properties of the obtained aerogels are comprehensively compared. Supercritical drying proves advantageous for aerogel formation, resulting in materials with lower density and higher surface area than their freeze-dried counterparts at each concentration level. The use of acetone for supercritical drying contributes to reduce the shrinkage rates compared to ethanol. This decrease is attributed to the formation of a more rigid hydrogel during solvent exchange. Freeze-drying exhibits the lowest shrinkage rates and relatively higher porosity. The presence of lignin in the nanofibers influences the microstructure, yielding smoother and thicker pore walls. This study contributes to the comprehensive understanding of the intricate factors shaping nanocellulose aerogel properties, paving the way for the development of innovative and environmentally-friendly materials.

Self-adhesive ionic cable derived from natural bark as osmotic energy generator

Osmotic energy conversion technology plays an increasingly important role as clean energy alternatives. However, the excessive use of non-renewable materials in osmotic energy harvesting can lead to serious environmental pollution. Herein, we design a low-cost, eco-friendly, and high-ion-conductance ionic cable directly from natural Eucommia ulmoides bark owing to its unique sandwich structure and abundant charged nanochannels within the well-aligned lignocellulose nanofibers. In the cable, the natural biopolymer E. ulmoides gum (EUG) acts as a bio-adhesive tightly holding cellulose fibers together, rendering it with high morphological stability. The as-prepared ionic cable shows excellent ion conductance of 3.36 × 10−3 S cm−1, far surpassing the performance of natural bark (2.58 × 10−4 S cm−1). This work utilizes the natural E. ulmoides bark components and its unique lignocellulose-EUG sandwich structure to construct fully biomass-based cable with high-ion-conductance and water-stable, providing a sustainable strategy to accelerate the implementation of clean osmotic energy harvesting and forest waste utilization.

3D printing of phase change material-based Pickering emulsion gel for solar-thermal-electric conversion

The rapid global increase in the consumption of fossil energy had led to urgent environmental issues, thereby prompting vigorous efforts towards the development and application of renewable energy. The effective encapsulation of phase change materials (PCMs) is crucial and indispensable for achieving high-performance solar-thermal energy harvesting and storage. However, challenges persist in the manufacturing of PCMs encapsulations with customizable and intricate structures to meet diverse scenarios. Herein, a PCMs Pickering emulsion gel ink, based on lignocellulosic nanofibers (LCNFs)/graphene oxide (GO) nanosheets stabilized paraffin, has been prepared to fabricate customized PCMs using 3D printing techniques for solar-thermal-electric conversion applications. The micro-nano matrix consisting of LCNFs and GO nanosheets provides a stable oil/water (O/W) interface, limits movements and deformability of paraffin microsphere, thereby increasing the viscosity and stiffness of the PCMs Pickering emulsion gel ink to ensure its excellent rheological property. Moreover, the LCNFs enhance printability and shape fidelity of the ink as interfacial stabilizer and viscosity modifier, which facilitates the manufacture of various 3D geometries. As a result, the designed concave PCMs solar harvester not only exhibits exceptional solar-to-thermal conversion efficiency, but also effectively mitigates heat loss and enables efficient heat storage for electricity generation. Our work demonstrates a new way toward utilization of LCNFs as PCMs emulsion stabilizers and encapsulants in PCMs and the fabrication customized PCMs architectures for solar-thermal-electric conversion applications using 3D printing techniques.

Lignocellulose nanofiber and starch for surface application on recycled linerboard

In a paper production line, starch is widely used for surface treatment and strengthening of linerboard at a size press. Also, the application of lignocellulose nanofibers (LCNFs) is growing because of its relatively low production energy demand, cost, and less hydrophilic nature in comparison to lignin-free nanofibers. Therefore, the addition of LCNFs to starch for paper surface treatment to reinforce the starch film and improve certain physical and mechanical properties of recycled linerboard was investigated in this work. Various LCNF/starch ratios were homogenized and then applied on the paperboard surface. The results revealed that a low mixing ratio of LCNF (5%) with starch improved the tensile index of the recycled paperboard, and at 50% LCNF content in the surface-treating material, film forming on the linerboard was observed in field emission-scanning electron microscopy images. In the case of 95% LCNF addition to starch, bending stiffness was significantly increased. Additionally, the viscosity of the sizing suspension was studied as a crucial parameter in the process and was found to increase significantly following the addition of LCNF.

Fabraction of edible bio-nanocomposite coatings from pectin-containing lignocellulosic nanofibers isolated from apple pomace

Minimally processed fruits are increasingly demanded in modern society, but the management of perishable waste pomaces (WPs) and the products' short shelf-life are still big issues. Here, a facile approach of reconstruing apple pomace (AP) into edible bio-nanocomposite coatings of fresh-cutting apple slices was successfully developed through alkaline demethylation followed by high-pressure homogenization. The fibrillation of AP fibers is largely improved by -COO− at a concentration of 1.23 mmol g−1, which is released through alkaline demethylation of pectin, instead of relying on intricated or costly cellulose modifications. The average width of AP nanofibers (AP-NFs) downsizes to 18 nm. By casting, AP-NFs fabricate homogeneous films with comparable transparency (56 % at 600 nm), superior mechanical strength (6.4 GPa of Young modulus and 81.7 MPa of strength) and oxygen barrier properties (79 mL μm m−2 day−1 bar−1), and non-toxicity. Moreover, the AP-NF coatings effectively extend shelf life of apple slices by inhibiting browning and respiration, and retain firmness. This research demonstrates a way to valorize WPs as edible coatings for fruit packaging.

Impact of lignocellulosic nanofiber source on the performance of polylactic acid

AbstractComposites based on polylactic acid (PLA) were developed, using lignocellulosic nanofibers (LCNF) dispersed in polyethylene glycol (PEG). To evaluate the impact of LCNF sources, suspensions were prepared from different pulps, including only cellulose; other with cellulose and hemicellulose; and cellulose, hemicellulose, and lignin. The PLA/PEG ratio was 80/20, with LCNF concentrations of 1.25%, 2.5%, and 3.75% (w/w) relative to the PLA/PEG weight. The best results were achieved with 2.5% (w/w) of LCNF containing a blend of cellulose and hemicellulose, showing a 26% increase in tensile strength and 102% in Young's modulus compared with the PLA/PEG matrix. The hemicellulose in LCNF acts as a physical barrier between cellulose chains, demonstrating a lower tendency for agglomeration and greater compatibility with PEG and PLA, as evidenced by decreased zeta potential due to the adsorption of PEG and shifts in the CO peak in the FTIR spectra. At 3.75 LCNF concentration, micrometer‐sized fibers were observed in SEM images, impacting the mechanical properties of the composites. Thermograms show no phase separation, and the change in crystallinity due to the addition of nanofibers has minimal influence on mechanical properties. These findings highlight the importance of selecting appropriate lignocellulosic nanoparticles for improved material performance.

Efficient capture of particulate matter with composite air filters comprising bamboo-derived nanofiber and base paper

Particulate-matter (PM) air filters comprising chemically synthesized polymers and petroleum-based materials are not environmentally sustainable because they do not biodegrade, causing secondary environmental pollution. To overcome this problem, we synthesized and analyzed the PM-capturing performance of composite sandwich-structured air filters containing bamboo-derived lignocellulose nanofibers and lignocellulose base paper. Bamboo pulp was produced through an organosolv process, and lignocellulose nanofibers and lignocellulose base paper were manufactured via electrospinning and paper processes, respectively. The manufacturing process was not only optimized via a rheological analysis of the precursor solution with different mixed solvent composition (6:4, 5:5, and 4:6 of 1-ethyl-3-methylimidazolium acetate:dimethylformamide) and different lignocellulose weight percent (3.3, 4.0, and 4.6 wt%), but also via nanofiber characterization, including electrospinnability, diameter distribution, and basis weight. The base paper condition was optimized based on analyses of the air permeability, PM filtration efficiency, and strength according to the paper thickness of 0.38 ± 0.05 and 0.10 ± 0.05 mm. As the lignocellulose nanofibers and base paper effectively captured particles smaller and larger than 2.5 μm, respectively, the structure of their composite sandwich-structured air filter was optimized to improve its PM-capturing performance. The study results provide new insights into the manufacturing of highly efficient PM air filters suitable for practical applications with diverse PM size distributions.

A lignocellulose nanofibril-poly(vinyl alcohol) hydrogel with controlled drug delivery for wound healing

Employing lignocellulosic nanofibers (LCNF) with natural, high specific mechanical performance and abundant functional groups to design a hydrogel as a drug-sustained release carrier, which conforms to the concept of green and sustainable development. Herein, we facilely extracted carboxylated lignocellulose nanofibrils (CLCNF) from bagasse via a deep eutectic solvent (DES) and mechanical defibrillation-based strategy. The CLCNF was crosslinked with poly(vinyl alcohol) (PVA) to obtain a nanocomposite hydrogel (PVA/CLCNF/B) whereupon the mechanical strength and drug release behavior were improved in the process. Consequently, the lignocellulose nanocomposite hydrogel presented a high compression modulus (3.92 MPa) and significant sustained-release effect with a release rate of 80.73 % after 336 h. The delivery behavior of the PVA/CLCNF/B composite hydrogel could be controlled by acidic pH conditions. The TH release kinetics of PVA/CLCNF/B hydrogel in different phosphate buffer saline (PBS) followed the Korsmeyer-Peppas model better, and the release of TH occurred through the Fickian diffusion mechanism. Importantly, in vivo experiments and histopathological studies showed that TH-loaded PVA/CLCNF/B hydrogel had a superior pro-healing rate. Overall, the incorporation of CLCNF into a hydrogel may have considerable potential as a drug delivery carrier for drug release and therapy. SynopsisAdding the CLCNF from bagasse into PVA dispersions obtained a hydrogel for pH-responsive drug delivery can accelerate wound healing.

Production of chitosan-based composite film reinforced with lignin-rich lignocellulose nanofibers from rice husk

Lignocellulosic nanofibers (LCNFs), implying lignin-containing cellulose fibers, maintain the properties of both lignin and cellulose, which are hydrophobic and hydrophilic, respectively. The presence of hydrophobic lignin in LCNFs is expected to be an economical and attractive option that can improve the thermal and mechanical properties of polymers. Thus, this study was conducted to produce lignin-rich LCNFs from sugar-rich waste obtained from rice husks after acidic pretreatment. The LCNFs were produced from the lignin-rich solid fractions obtained after pretreatment and enzymatic hydrolysis, which were then incorporated as an additive into a chitosan-based film. The variations in lignin content in the range of approximately 50.6%–66.8% in differently obtained LCNFs gave significantly different optical strengths and mechanical properties. These controllable processes may allow for customized film formation. Additionally, the glucose-rich liquid fractions obtained after pretreatment and enzymatic hydrolysis were used as a substrate for ethanol fermentation to achieve total utilization of rice husk biomass waste. In conclusion, the lignin-rich biomass fraction holds promise as a suitable material for chitosan-LCNF film and has the potential to increase the economic feasibility of the biomaterial industry.

Effect of lignin in cellulose nanofibers on biodegradation and seed germination

AbstractPure cellulose nanofibers (CNFs) rapidly degrade in soil, limiting their prospective applications in agriculture. We incorporated lignin into CNFs as an antimicrobial and crosslinking agent to control the biodegradation rate. CNFs with different lignin concentrations were prepared by mechanochemical treatment in the presence of choline chloride-urea deep eutectic solvent. These were characterized using conductometric titration, scanning electron microscopy, and FT-IR. The fibers were applied to soil to determine the effect of lignin on soil respiration and nanocellulose degradation, and were used as a substrate for radish and cress seed germination. Modifying the lignin content of the fibers successfully modulated the biodegradation rate in soil. Fibers containing 35% lignin degraded 5.7% in 14 days, while fibers with 20% lignin degraded 20.8% in 14 days. Nanofiber suspensions showed low chemical inhibition for the germination of radish and cress seeds but higher lignin contents reduced the imbibition rate as a seed coating. This study presents the first use of lignin to control the biodegradation rate of cellulose nanofibers in a one-pot, scalable and sustainable system, allowing the advancement of lignocellulose nanofibers for applications such as seed coatings, mulches, and controlled release fertilizers. Graphical Abstract

Bifunctional lignocellulose nanofiber hydrogel possessing intriguing pH-responsiveness and self-healing capability towards wound healing applications

Lignocellulose nanofibers (LCNF) obtained from agricultural waste are potential candidates for enhancing composite materials because of their excellent mechanical properties, abundant groups and high biocompatibility. However, the application of LCNF has received limited attention to date from researchers in the healthcare field. Herein, based on the bifunctional group (carboxyl and aldehyde groups) modified LCNF (DCLCNF) and chitosan (CS), we developed a multifunctional bio-based hydrogel (CS-DCLCNF). The addition of lignin-containing DCLCNF strengthened the internal crosslinking and the intermolecular interaction of hydrogels, and the presence of lignin and carboxyl groups increased the mechanical strength of the hydrogel and the adsorption of aromatic drugs. Results revealed that the hydrogels exhibited self-healing, injectable, and high swelling rates. The hydrogels had favorable mechanical strength (G'max of ~16.60 kPa), and the maximum compressive stress was 24 kPa. Moreover, the entire tetracycline hydrochloride (TH) release process was slow and pH-responsive, because of the rich noncovalent and π–π interactions between DCLCNF and TH. The hydrogels also exhibited excellent biocompatibility and antibacterial properties. Notably, the wound healing experiment showed that the hydrogels were beneficial in accelerating wounds healing, which could heal completely in 13 days. Therefore, CS-DCLCNF hydrogels may have promising applications in drug delivery for wound healing.

Bio-based nanomaterial suspensions as sprayable coatings for maintaining blueberry postharvest quality

The growing concerns about postharvest fruit spoilage demand sustainable active coating materials with high performance. In this work, bioactive spray coating suspensions were developed for the postharvest preservation of blueberries using chitosan, cellulose, and lignocellulose nanofibers (ChNFs, CNFs, and LCNFs), sodium alginate (SA), and tea tree essential oil (TTO). Characteristics, including the rheological properties of coatings and the effect on physicochemical postharvest quality parameters of blueberry fruit were investigated. The nanomaterials and SA were shown to make stable and sprayable coating suspensions with high surface charge (zeta potential value of −61.3 mV), shear thinning behavior, steady viscosity, and outstanding viscoelastic behavior from their ability to restore fibrous network structure and ion strength of SA to inhibit nanofibers aggregation. The coatings with LCNFs and SA were more effective in retarding moisture loss of postharvest blueberries during storage compared with coatings without LCNFs and SA. Blueberries coated with ChNF/LCNF/SA/TTO had a soluble solids content (SSC) increase of 16.2% after 15 storage days, while uncoated and other coated blueberries had more than a 21.7% SSC increase. In addition, the ChNF/LCNF/SA/TTO coating had an entangled matrix structure and enhanced hydrophobicity, improving gas barrier performance on the blueberry surface. As a result, the coating was able to preserve the moisture, stiffness, firmness, and individual sugar contents of blueberries during storage. Utilizing nanomaterials and other natural polysaccharides in coatings can offer an economically feasible and sustainable approach for functionalizing biomass materials to preserve fruits.

Low-energy extraction of lignocellulose nanofibers from fresh Musa basjoo pseudo-stem

This study presents a novel approach for the extraction of cellulose nanofibers (CNF) and lignocellulose nanofibers (LCNF) from Musa basjoo pseudo-stems, a relative of bananas, without the need for extensive drying. Instead, wet pseudo-stems were compressed and treated with NaOH solutions at varying temperatures and durations. The extracted material exhibited the characteristic peaks of cellulose I in X-ray diffraction (XRD) patterns, similar to those obtained from dried pseudo-stems. Fourier-transform infrared (FT-IR) spectroscopy confirmed the presence of cellulose I in the treated material and lignocellulose nanofiber clearly shown at 1600-1500, 1421, 1365, and 1161 cm-1. Composition analysis by Van Soest fiber analysis revealed a higher cellulose content in the treated material of wet pseudo-stems compared to that obtained from dried pseudo-stems, indicating the effectiveness of this low-energy extraction method. Meanwhile, field-emission scanning electron microscopy (FE-SEM) images demonstrated clear LCNF in the nanometer scale fibers after NaOH treatment. Overall, this study successfully demonstrated the extraction of LCNF from wet pseudo-stems of Musa basjoo with NaOH treatment at 70°C for 3 hours with 80% extraction result, providing a more efficient and low-energy approach for utilizing waste from Musa basjoo and bananas.

Evaluation of the effect of nanocellulose edible coating on strawberries inoculated with Aspergillus flavus through image analysis

The impact of a coating solution containing chitosan, lignocellulosic nanofibers (LCNF), and raspberry leaf extract on strawberry quality was assessed. Strawberries were coated, inoculated with Aspergillus flavus (a major aflatoxin producer), and stored at 5 ± 1 °C for 16 days. An automated fruit quality evaluation system was developed, and daily images were taken for analysis. ImageJ software was used to evaluate colour, size loss, and fungal damage. Coating solution significantly reduced fruit size loss, with coated strawberries showing 18.4 ± 12.8% size loss after 16 days, compared to 30.2 ± 8.4% in the control group and 25 ± 10.7% in uncoated strawberries. Regarding colour, lower colour changes were observed in coated fruit compared to the control during storage (p ≤ 0.05). Fungal damage did not significantly differ between treatments during storage (p > 0.05). Furthermore, the study demonstrated that image analysis and visual estimation methods for assessing fruit fungal damage yielded similar results, with a strong correlation (R2 = 0.87). This suggests that the proposed image analysis methodology is effective for the assessment of fungal damage in strawberries compared to visual estimation. Chitosan-LCNF-raspberry extract coating solution shows promise in enhancing strawberry quality by reducing size loss during storage and managing fungal development.

Nanoscopic lignin mapping on cellulose nanofibers via scanning transmission electron microscopy and atomic force microscopy

Cellulose has been developed as an alternative to petrochemical materials. By comparison with refined nanofibers (RCNFs), lignocellulose nanofibers (LCNFs) show particular promise because it is produced from biomass using only mild pretreatment. The mechanical properties of LCNFs depend on the contained lignin. However, the microscopic location of the lignin contained in LCNFs has not been determined. Thus, we developed two methods to detect and visualize lignin. One uses a scanning transmission electron microscope (STEM) equipped with an energy dispersive X-ray spectroscopy detector. The other method uses an atomic force microscope (AFM) equipped with a cantilever coated with an aromatic molecule. Both methods revealed that the lignin in LCNFs covers a thin cellulose fiber and is precipitated in a grained structure. In particular, the AFM system was able to determine the nanoscopic location of lignin-rich areas. The present study establishes a strong tool for analyzing the characteristics of lignin-containing materials.Graphical abstract

Improved drainage of LNFC-reinforced recycled pulp and mechanical properties of end papers by the zeolite-chitosan microparticle drainage aid system

Good drainage of the pulp suspension is vitally important for stable papermaking. Although the addition of lignocellulosic nanofibers (LNFC) in pulp could highly reinforce the end paper sheets, the application of LNFC could diminished the pulp drainage. To solve this problem, the impact of the zeolite-chitosan and bentonite-chitosan microparticle drainage aid systems on the LNFC-reinforced recycled pulp was systematically investigated. Results indicated that the mentioned microparticle systems improved the drainage and retention especially in applying 1% chitosan with 0.3% zeolite. In mechanical properties, applying the microparticle systems, not only did not deteriorate these properties, but also improved most of them, especially in treatment containing zeolite-chitosan. It seems that the improved pulp drainage and the mechanical properties of the end papers was due to successful mission of microparticle system and synergistic interactions of pulp fibres, LNFC, chitosan, and zeolite, which could also lead to denser and more uniform structure of handsheets.

Raspberry (Rubus idaeus L.) waste-derived nanocellulose for circular application in edible films and coatings

Due to the overuse of petroleum-derived polymers and the consumer demand for nutritious and healthy products that can maintain their quality over longer periods of time, there is a need for new sustainable packaging systems that fulfill these requirements. Lignocellulosic biomass, particularly agricultural pruning residues, offer great potential for obtaining biopolymers through biorefining processes. In this study, raspberry pruning residues were used to produce lignocellulose nanofibers (LCNF) and cellulose nanofibers (CNF), by varying the intensity of TEMPO-mediated oxidation pretreatment (5 and 10 mmol/g) and examining the amount of residual lignin and its impact on reinforcement capacity in food edible films and coating using chitosan-based formulations. The addition of CNF/LCNF up to 0.05 g/g of film, improved the mechanical properties of films, with Tensile Strength (TS) reaching a highest value of 40.98 MPa for 0.03 g/g LCNF-TO5 films. The presence of residual lignin in LCNF enhanced the optical properties of the films, particularly in terms of UV light blocking, with values of 84.56% achieved for 0.15 g/g LCNF-TO5 samples. The use of a coating with concentrations of up to 0.1 g/g LCNF resulted in improved firmness values and lower counts of aerobic mesophilic bacteria (AMB) after 7 days of storage.

Harvesting value from agricultural waste: Dimensionally stable fiberboards and particleboards with enhanced mechanical performance and fire retardancy through the use of lignocellulosic nanofibers

The present work provides a comprehensive study on the utilization of rapeseed stalks, an agricultural waste, as a raw material for the production of resin-free fiberboards and particleboards, using LCNFs as binder. The rapeseed stalks underwent appropriate crushing and fibrillation and were combined with a novel class of lignocellulosic nanofibers (LCNFs) derived from date palm waste, another agricultural residue. The incorporation of LCNFs in both fiberboards and particleboards resulted in increased density and enhanced mechanical properties, dimensional stability, and fire resistance. These positive effects can be attributed to several factors. Firstly, the incorporation of LCNFs led to a reduction in porosity, positively impacting the modulus of rupture, modulus of elasticity, and internal bonding of the produced fiberboards and particleboards. Notably, fiberboards containing 15 wt% LCNF exhibited superior specific properties compared to our commercial reference. Additionally, this densification effect mitigated moisture absorption and thickness swelling, as even a 2 wt% incorporation of LCNF in fiberboards showed reduced values for both properties. Secondly, the high lignin content of the LCNFs contributed to decreased hydrophilicity in the fiberboards and particleboards, leading to significant improvements in water contact angle, water absorption, and thickness swelling. Lastly, the increased density of the fiberboards and particleboards resulted in improved fire resistance, with flame propagation time being higher for all boards containing LCNFs, even at low content (2 wt%), compared to the commercial fiberboard. Notably, fiberboards demonstrated superior performance compared to particleboards, attributed to factors such as low cohesion, particle heterogeneity, and excessive porosity. Overall, this study demonstrates the feasibility of utilizing agricultural waste as a raw material for board production, eliminating the need for urea-formaldehyde resins and paraffin waxes commonly found in commercial fiberboards.