Nanocellulose Applications in Wood Adhesives—Review

S. K. Vineeth, Ravindra V. Gadhave^*, Pradeep T. Gadekar

Department of Polymer and Surface Engineering, Institute of Chemical Technology, Mumbai, India.

DOI: 10.4236/ojpchem.2019.94006                

Abstract

Bio-based materials open a new world of possibilities in every field due to its independence from the petrochemical origin. Moreover, concerns on environmental footprints and toxicity of synthetic adhesives made scientists investigate the utilization of biomaterials for wood adhesives. In this perspective, nanocellulose as a sustainable and cheap bio-nanomaterial provides a better alternative to conventional adhesive based on formaldehyde-containing condensation resins. Property of nanocellulose to act as both binders and as structural reinforcement in various adhesive systems adds to its potential. Besides by reducing the harmful emission of formaldehyde, it also can improve the mechanical properties and enhance performance of adhesives. This review paper aims to point out the potential application of nanocellulose based wood adhesives compared to petroleum-based conventional systems beyond renewability. New functionalities through structural modification in nanocellulose could bring a replacement with the synthetic adhesive systems which will play a significant role in future bio-economy.

Keywords

Nanocellulose, Reinforcement, Binding, Polyvinyl Acetate, Wood Adhesive

1. Introduction

Synthesis of polymers from bio-based renewable resources has received much acceptance due to the increasing environmental awareness and growing need to decrease the usage of conventional petroleum-based sources. In wood adhesive technology, formaldehyde-based synthetic adhesives such as urea-formaldehyde resin, phenol-formaldehyde resin, and melamine-formaldehyde are the predominant adhesives for the manufacture of various wood panels [1]. Formaldehyde emissions are mainly due to residual unreacted formaldehyde and slow adhesive hydrolysis under hot/humid conditions during the production and use of panel [2] [3]. Because of formaldehyde emissions, it has been proved that formaldehyde-based adhesives are not environmentally friendly products [4]. Even though the majority of wood adhesives are still petroleum-based, recent studies on the toxicity of formaldehyde [2] [5] [6] as a harmful substance accelerated scientists for finding an alternate source. In this aspect biopolymer based wood adhesives have a huge potential with reduced formaldehyde emission [7] [8] [9]. Another problem with phenolic resin wood adhesive is its brittleness; studies showed that this problem could be overcome by reinforcement with biomaterial, microcrystalline cellulose [10]. Hence to reduce formaldehyde and volatile organic content emission and for sustainable development, bio-based materials could be one of the alternatives beyond its renewability [11] [12] [13]. Researchers have a great interest in traditionally bio-based binders, such as starch [14] [15] [16] [17] [18], soy protein [19] [20] [21] [22] [23] or renewable rubber [24] [25] [26] [27], use of modified vegetable oils or lignin derivatives [28] - [34], and various cellulosic materials [35] - [44] for application in adhesive field.

Among these biopolymers, cellulose is the most abundant renewable biomaterial [45] and its natural affinity for self-adhesion makes it a potential material in adhesion science. Cellulose is a polysaccharide macromolecule with its advantage of abundant availability, economical production, excellent mechanical properties, possibilities for making biocomposites and its ability for functionalization makes it a unique material [46] [47]. Isolated cellulosic materials with one dimension in the nanometer range are referred to generically as nanocellulose [48]. They may be cellulose nanocrystals (NCC or CNC), nano fibrillated celluloses (CNF) and bacterial nanocellulose [49]. It can be achieved through mechanical or chemical treatments [50]. Nanocellulose shows extraordinary properties compared to the bulk material [51] [52] [53] [54] [55] and the binding properties of nanocellulose have been investigated in various studies [56] [57] [58]. Chemical modification of nanocellulose and its reinforcing properties in polymer matrices adds its application, improving the mechanical properties of nanocomposite [59] [60] [61] [62]. In conventional adhesives, nanocellulose hence finds application as a bio based reinforcing agent [63] [64]. This is also true in the case of wood adhesives, where introduction to nanocellulose made it possible for incorporating an abundant, sustainable, and cheap nano-bio-material for property improvement [65] [66] [67] [68]. In addition to applications of nanocellulose as ecofriendly binder [42] [58] [69] [70] it also finds application as a binder for Lithium battery electrodes [71] [72] [73], excellent barrier properties of cellulosic materials [74] have been made improved properties and extended its reach in various fields such as gas barrier, water barrier [75] and flame retarding applications [76], packaging applications, paper coating industries with nanocellulose and micro cellulose [77].

This review paper focuses the applicability of cellulose nanomaterials in wood adhesive field. The recent studies on binding property and reinforcement with nanocellulose, including nanocrystalline and nanofibrous cellulose in various wood adhesives systems are also been discussed. This work therefore aims to provide efforts to showcase the potential applications of nanocellulose in wood adhesives both as a reinforcing agent and binder, therefore a step to improve mechanical property of adhesive nanocomposite and to replace common carcinogenic adhesive ingredients, particularly formaldehyde in wood-adhesive research.

2. Nanocellulose Application in Wood Adhesives

There are several types of wood panels, including: laminated wood panels, agglomerated wood panels or wood fiber panels. The acceptance of wood in various fields, including furniture manufacturing, construction, and building sector hassled to a high demand for wood adhesive. Among the several opportunities offered by nanotechnology for the forest products industry, the reinforcement of adhesives with nanocellulose [78] has been already identified as a potential opportunity, which has been explored. It has shown improvement in both the physical and mechanical properties of the panels [40]. Reconstituted products, such as particleboard, oriented strand board (also known as flakeboard) and plywood panels, among others, appear as an alternative to solid wood, needs an improvement in the characteristics of the raw material. However, the quality of the final product depends mainly on adhesion technology. The plywood panels are composed of wood overlapping and bonded with adhesives, mainly phenol-formaldehyde and urea-formaldehyde, under pressure and temperature so that they cross their fibers at an angle of 90˚. Particleboard wood panels may be defined with randomly arranged small particles, bonded using adhesives and glued using heat and pressure. The most used adhesives in the production of panels of particleboard wood are the synthetic ones such as urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde.

The benefits of using nanocellulose as reinforcements in adhesives for the production of reconstituted wood panels include: the possibility of altering the properties of adhesives, gain in mechanical and physical properties of panels and reduction in formaldehyde emissions by using synthetic adhesives. It was observed a variation of viscosity with the increasing percentage of adding cellulose nanocrystals (CNC) in the glue [79]. Addition of cellulose nanofibers (CNFs) in urea-formaldehyde and melamine-urea-formaldehyde adhesives showed reinforcing nature of cellulose nanofibers [68]. Improvements in adhesives fracture energy, and fracture toughness enhanced the mechanical board properties, which could be confirmed by reinforcement of CNF in the adhesive. A similar study in which CNF were investigated as a binder in the formulation of particleboard panels [80]. The modulus of rupture, modulus of elasticity, internal bond, water absorption, and thickness swelling properties were tested. Particleboard panels met the industry requirements in terms of mechanical properties for low-density grades. J. Cui et al. [81] conducted a study for investigating the performance enhancement of tannin-based particleboards with cellulose nanofibers. Internal bond strength and viscosity increased on addition of 2% of cellulose nanofibers. The modulus of elasticity and modulus of rupture of the resins was also notably increased while thickness swelling of the panels was not affected. Kojima et al. conducted a study on the binding effect of cellulose nanofibers in wood flour board as a reinforcement [70]. The physical and mechanical properties of wood flour boards could be improved with the addition of CNF because of binding effect between the CNF and wood flour particles. A similar study on the evaluation of binding effects in wood flour board containing lingo cellulose nanofibers showed a significant enhancement of physical and mechanical properties of the board [42]. The study focused on reinforcement effects of lingo-cellulose nanofiber on fiberboards made from softwood and hardwood fiber was conducted [82]. In the study reinforcement effects of lingo-cellulose nanofiber on fiberboards was observed, due to close binding between lingo-cellulose nanofiber and wood fibers. Urea-formaldehyde based wood adhesive filled with cellulose nanofibrils were studied for fracture mechanical properties [38]. The highest fracture energy values were observed for urea-formaldehyde bonds filled with untreated nanofibrils, but bonds filled with TEMPO-oxidized fibrils showed inferior properties.

In a study on micro fibrillated-cellulose-urea-formaldehyde adhesives and its effect on the mechanical properties of laminated veneer lumber, the viscosity and gel time of the urea-formaldehyde adhesives increased with an increasing amount of the micro fibrillated-cellulose [41]. Limited amounts of the micro fibrillated-cellulose suspension in the urea-formaldehyde adhesive formulation significantly improved the mechanical performance of urea-formaldehyde bonds. Microfibrillated cellulose enhanced the strength properties of the adhesive and improves ductility of the adhesive.

3. Nanocellulose Based Polyvinyl Acetate Adhesives

Polyvinyl acetate (PVA) is an excellent alternative to replace some wood adhesives containing formaldehyde. PVA is a linear and thermoplastic polymer. It is water-soluble, biodegradable with excellent chemical resistance and has no toxic action on the human body. As a wood adhesive, utilization of PVA is effortless [90]. For curing PVA, it does not need high temperatures. Poor performance of PVA towards humid conditions and at elevated temperature contributes to the main drawback and limits the usage. So far two approaches have been used to increase the performance of PVA: 1) Copolymerizing vinyl acetate with more hydrophobic monomers or functional monomers [91], and 2) blending PVA with other adhesives or hardeners [92] [93].

A study conducted by Jiang et al. [67] in which commercial polyvinyl acetate and starch adhesives were mixed with dicarboxylic acid cellulose nanofibrils (CNF). On adding optimum amount of CNF, the lap-joint strength increased to 74.5%. Properties were inferior at higher loading. In addition to reinforcing effects, increase in viscosity and shear strength of wood joints with polyvinyl acetate adhesives by CNF, water resistance and enhancement of mechanical properties at wet condition by adding 7% of CNF observed in [94]. Few published studies have done modification of polyvinyl alcohol by cross-linking [95]. Dynamic mechanical analysis (DMA), and wood bonding of polyvinyl acetate and polyvinyl alcohol latex reinforced with cellulose nanofibrils were studied [40]. Increasing the amounts of cellulose nanofibrils (treated or untreated) led to increasing reinforcing effects in the glassy state. Due to the interactions between the cellulose fibrils network and the hydrophilic polyvinyl alcohol matrixled to complete disappearance of the polyvinyl alcohol glass transition for some fibril types and contents. Kaboorani et al. [39] used nanocrystalline cellulose (NCC) in the wood adhesive to improve the performance of polyvinyl acetate. The study conducted addition of NCC at different loadings (1%, 2%, and 3%) to polyvinyl acetate and usage of the blends as a binder for wood. The block shear tests demonstrate that NCC can improve the bonding strength of polyvinyl acetate in all conditions. Thermal stability, hardness, modulus of elasticity and creep of polyvinyl acetate film were also enhanced by the addition of NCC.

4. Conclusions

Nanocelluloses (mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC)) represent an abundant natural resource of green and sustainable materials. Depending on the type of nanocellulose, modification of its structure and compatibility between polymer matrixes, performance property of adhesives enhanced even by addition of small amount. The current review highlighted some of the most recent advances and applications of these nanomaterials both as binder and reinforcing agent focusing the wood-based adhesives. Study proves that addition of these biobased nanomaterials could drastically enhance mechanical properties, performance properties and improve adhesive strength of wood adhesives. The benefits of using nanocellulose in the field of wood adhesive open the possibility of altering the properties of adhesives, gain in mechanical and physical properties of wood by its reinforcement and reduction in formaldehyde emissions by using synthetic adhesives.

Although applications of nanocellulose in the field of wood adhesives are at its infancy, it is foreseeable that there is a bright future for application of nanocellulose in the wood adhesive industry. Undoubtedly, there are many challenges for researchers in this field to overcome, and further intensive researches are needed.

5. Futuristic Approaches for the Development of Nanocellulose Based Wood Adhesive

Futuristic research in development and optimization of nanocellulose wood adhesives will be to increase the bonding between nanocellulose and base polymer matrix. This can be achieved in many ways. One such example can be adopting novel functionalizing approaches that permit nanocellulose to extend its applicability in wood adhesives. This includes cross-linking nanocellulose by suitable chemistry, functionalization by Silane coupling agents with adhesive system and nanocellulose grafted wood adhesives. This helps to improve dispersion and redistribution of nanomaterial inside the polymer matrix hence increment in the interaction with nanocellulose, adhesive, and substrate. Another area to be improved is in the water-resistance of nanocellulose based adhesives. One such possibility is functionalizing nanocellulose through chemical modification, cross-linking to get denser network or mixing with synthetic adhesives, and improving its interface for better compatibility.

Conflicts of Interest

The authors declare no conflicts of interest regarding the publication of this paper.

References

[1]	Zhao, L.F., Liu, Y., Xu, Z.D., Zhang, Y.Z., Zhao, F. and Zhang, S.B. (2011) State of Research and Trends in Development of Wood Adhesives. Forestry Studies in China, 13, 321-326. https://doi.org/10.1007/s11632-013-0401-9
[2]	He, Z., Zhang, Y. and Wei, W. (2012) Formaldehyde and VOC Emissions at Different Manufacturing Stages of Wood-Based Panels. Building and Environment, 47, 197-204. https://doi.org/10.1016/j.buildenv.2011.07.023
[3]	Böhm, M., Salem, M.Z.M. and Srba, J. (2012) Formaldehyde Emission Monitoring from a Variety of Solid Wood, Plywood, Blockboard and Flooring Products Manufactured for Building and Furnishing Materials. Journal of Hazardous Materials, 221-222, 68-79. https://doi.org/10.1016/j.jhazmat.2012.04.013
[4]	Roffael, E. (2006) Volatile Organic Compounds and Formaldehyde in Nature, Wood and Wood Based Panels. Holz als Roh-und Werkstoff, 64, 144-149. https://doi.org/10.1007/s00107-005-0061-0
[5]	Arts, J.H.E., Rennen, M.A.J. and De Heer, C. (2006) Inhaled Formaldehyde: Evaluation of Sensory Irritation in Relation to Carcinogenicity. Regulatory Toxicology and Pharmacology, 44, 144-160. https://doi.org/10.1016/j.yrtph.2005.11.006
[6]	Beane Freeman, L.E., et al. (2009) Mortality from Lymphohematopoietic Malignancies among Workers in Formaldehyde Industries: The National Cancer Institute Cohort. Journal of the National Cancer Institute, 101, 751-761. https://doi.org/10.1093/jnci/djp096
[7]	Navarrete, P., et al. (2012) Low Formaldehyde Emitting Biobased Wood Adhesives Manufactured from Mixtures of Tannin and Glyoxylated Lignin. Journal of Adhesion Science and Technology, 26, 1667-1684.
[8]	Hemmilä, V., Adamopoulos, S., Karlsson, O. and Kumar, A. (2017) Development of Sustainable Bio-Adhesives for Engineered Wood Panels: A Review. RSC Advances, 7, 38604-38630. https://doi.org/10.1039/C7RA06598A
[9]	Syed, L.C., Imam, H., Gordon, S.H. and Mao, L.J. (2001) Environmentally Friendly Wood Adhesive from a Renewable Plant Polymer: Characteristics and Optimization. Polymer Degradation and Stability, 1, 40-44.
[10]	Atta-obeng, E. (2011) Characterization of Phenol Formaldehyde Adhesive and Adhesive-Wood Particle Composites Reinforced with Microcrystalline Cellulose. Auburn University, Auburn.
[11]	Heinrich, L.A. (2019) Future Opportunities for Bio-Based Adhesives-Advantages beyond Renewability. Green Chemistry, 21, 1866-1888. https://doi.org/10.1039/C8GC03746A
[12]	Jang, Y., Huang, J. and Li, K. (2011) A New Formaldehyde-Free Wood Adhesive from Renewable Materials. International Journal of Adhesion and Adhesives, 31, 754-759. https://doi.org/10.1016/j.ijadhadh.2011.07.003
[13]	Prasittisopin, L. and Li, K. (2010) A New Method of Making Particleboard with a Formaldehyde-Free Soy-Based Adhesive. Composites Part A: Applied Science and Manufacturing, 41, 1447-1453. https://doi.org/10.1016/j.compositesa.2010.06.006
[14]	Gadhave, R.V., Mahanwar, P.A. and Gadekar, P.T. (2017) Starch-Based Adhesives for Wood/Wood Composite Bonding: Review. Open Journal of Polymer Chemistry, 7, 19-32. https://doi.org/10.4236/ojpchem.2017.72002
[15]	Gu, Y., Cheng, L., Gu, Z., Hong, Y., Li, Z. and Li, C. (2019) Preparation, Characterization and Properties of Starch-Based Adhesive for Wood-Based Panels. International Journal of Biological Macromolecules, 134, 247-254. https://doi.org/10.1016/j.ijbiomac.2019.04.088
[16]	Jiang, Y., Chen, Q., Tan, H., Gu, J. and Zhang, Y. (2019) A Low-Cost, Formaldehyde-Free, and High-Performance Starch-Based Wood Adhesive. BioResources, 14, 1405-1418.
[17]	Wang, Z., et al. (2019) Improvement of the Bonding Properties of Cassava Starch-Based Wood Adhesives by Using Different Types of Acrylic Ester. International Journal of Biological Macromolecules, 126, 603-611. https://doi.org/10.1016/j.ijbiomac.2018.12.113
[18]	Wang, Z., Li, Z., Gu, Z., Hong, Y. and Cheng, L. (2012) Preparation, Characterization and Properties of Starch-Based Wood Adhesive. Carbohydrate Polymers, 88, 699-706. https://doi.org/10.1016/j.carbpol.2012.01.023
[19]	Lei, H., Du, G., Wu, Z., Xi, X. and Dong, Z. (2014) Cross-Linked Soy-Based Wood Adhesives for Plywood. International Journal of Adhesion and Adhesives, 50, 199-203. https://doi.org/10.1016/j.ijadhadh.2014.01.026
[20]	Buddi, T., Muttil, N., Nageswara Rao, B. and Singh, S.K. (2015) Development of a Soya Based Adhesive in Plywood Manufacturing. Materials Today: Proceedings, 2, 3027-3031. https://doi.org/10.1016/j.matpr.2015.07.289
[21]	Vnucec, D., Kutnar, A. and Gorsek, A. (2017) Soy-Based Adhesives for Wood-Bonding: A Review. Journal of Adhesion Science and Technology, 31, 910-931. https://doi.org/10.1080/01694243.2016.1237278
[22]	Luo, J., Luo, J., Bai, Y., Gao, Q. and Li, J. (2016) A High Performance Soy Protein-Based Bio-Adhesive Enhanced with a Melamine/Epichlorohydrin Prepolymer and Its Application on Plywood. RSC Advances, 6, 67669-67676. https://doi.org/10.1039/C6RA15597A
[23]	Mo, X. and Sun, X.S. (2013) Soy Proteins as Plywood Adhesives: Formulation and Characterization. Journal of Adhesion Science and Technology, 27, 2014-2026. https://doi.org/10.1080/01694243.2012.696916
[24]	Khan, I. and Poh, B.T. (2011) Natural Rubber-Based Pressure-Sensitive Adhesives: A Review. Journal of Polymers and the Environment, 19, 793-811. https://doi.org/10.1007/s10924-011-0299-z
[25]	Radabutra, S., Khemthong, P., Saengsuwan, S. and Sangya, S. (2019) Preparation and Characterization of Natural Rubber Bio-Based Wood Adhesive: Effect of Total Solid Content, Viscosity, and Storage Time. Polymer Bulletin, 1-11. https://doi.org/10.1007/s00289-019-02881-1
[26]	Thuraisingam, J., Mishra, P., Gupta, A., Soubam, T. and Piah, B.M. (2019) Novel Natural Rubber Latex/Lignin-Based Bio-Adhesive: Synthesis and Its Application on Medium Density Fiber-Board. Iranian Polymer Journal, 28, 283-290. https://doi.org/10.1007/s13726-019-00696-5
[27]	John, N. and Joseph, R. (1997) Studies on Wood-to-Wood Bonding Adhesives Based on Natural Rubber Latex. Journal of Adhesion Science and Technology, 11, 225-232. https://doi.org/10.1163/156856197X00327
[28]	Gadhave, R.V., Srivastava, S., Mahanwar, P.A. and Gadekar, P.T. (2019) Lignin: Renewable Raw Material for Adhesive. Open Journal of Polymer Chemistry, 9, 27-38. https://doi.org/10.4236/ojpchem.2019.92003
[29]	Yang, Z., Peng, H., Wang, W. and Liu, T. (2010) Lignin-Based Polycondensation Resins for Wood Adhesives. Journal of Applied Polymer Science, 116, 2658-2667.
[30]	Khan, M.A., Ashraf, S.M. and Malhotra, V.P. (2004) Development and Characterization of a Wood Adhesive Using Bagasse Lignin. International Journal of Adhesion and Adhesives, 24, 485-493. https://doi.org/10.1016/j.ijadhadh.2004.01.003
[31]	Moubarik, A., Grimi, N., Boussetta, N. and Pizzi, A. (2013) Isolation and Characterization of Lignin from Moroccan Sugar Cane Bagasse: Production of Lignin-Phenol-Formaldehyde Wood Adhesive. Industrial Crops and Products, 45, 296-302. https://doi.org/10.1016/j.indcrop.2012.12.040
[32]	Hussin, M.H., Zhang, H.H., et al. (2017) Preparation of Environmental Friendly Phenol-Formaldehyde Wood Adhesive Modified with Kenaf Lignin. Beni-Suef University Journal of Basic and Applied Sciences, 6, 409-418. https://doi.org/10.1016/j.bjbas.2017.06.004
[33]	Kalami, S., Chen, N., Borazjani, H. and Nejad, M. (2018) Comparative Analysis of Different Lignins as Phenol Replacement in Phenolic Adhesive Formulations. Industrial Crops and Products, 125, 520-528. https://doi.org/10.1016/j.indcrop.2018.09.037
[34]	Sulaiman, N.S., Hashim, R., Sulaiman, O., Nasir, M., Amini, M.H.M. and Hiziroglu, S. (2018) Partial Replacement of Urea-Formaldehyde with Modified Oil Palm Starch Based Adhesive to Fabricate Particleboard. International Journal of Adhesion and Adhesives, 84, 1-8. https://doi.org/10.1016/j.ijadhadh.2018.02.002
[35]	David, N.H. (1989) Chapter 21 Cellulosic Adhesives. In: Richard, S.J.B., Hemingway, W. and Conner, A.H., Eds., Adhesives from Renewable Resources, ACS Symposium Series, American Chemical Society, Washington DC, 289-304. https://doi.org/10.1021/bk-1989-0385.ch021
[36]	Zhang, X.J. and Young, R.A. (2000) Adhesion Properties of Cellulose Films. MRS Online Proceeding Library Archive, 586, 1-29. https://doi.org/10.1557/PROC-586-157
[37]	Zhao, B.X., Wang, P., Zheng, T., Chen, C.Y. and Shu, J. (2006) Preparation and Adsorption Performance of a Cellulosic-Adsorbent Resin for Copper(II). Journal of Applied Polymer Science, 99, 2951-2956. https://doi.org/10.1002/app.22986
[38]	Veigel, S., Müller, U., Keckes, J., Obersriebnig, M. and Gindl-Altmutter, W. (2011) Cellulose Nanofibrils as Filler for Adhesives: Effect on Specific Fracture Energy of Solid Wood-Adhesive Bonds. Cellulose, 18, 1227-1237. https://doi.org/10.1007/s10570-011-9576-1
[39]	Kaboorani, A., Riedl, B., Blanchet, P., Fellin, M., Hosseinaei, O. and Wang, S. (2012) Nanocrystalline Cellulose (NCC): A Renewable Nano-Material for Polyvinyl Acetate (PVA) Adhesive. European Polymer Journal, 48, 1829-1837. https://doi.org/10.1016/j.eurpolymj.2012.08.008
[40]	López-Suevos, F., Eyholzer, C., Bordeanu, N. and Richter, K. (2010) DMA Analysis and Wood Bonding of PVAc Latex Reinforced with Cellulose Nanofibrils. Cellulose, 17, 387-398. https://doi.org/10.1007/s10570-010-9396-8
[41]	Ayrilmis, N., Kwon, J.H., Lee, S.H., Han, T.H. and Park, C.W. (2016) Microfibrillated-Cellulose-Modified Urea-Formaldehyde Adhesives with Different F/U Molar Ratios for Wood-Based Composites. Journal of Adhesion Science and Technology, 30, 2032-2043. https://doi.org/10.1080/01694243.2016.1175246
[42]	Kojima, Y., et al. (2014) Evaluation of Binding Effects in Wood Flour Board Containing Ligno-Cellulose Nanofibers. Materials (Basel), 6, 6853-6864. https://doi.org/10.3390/ma7096853
[43]	Cataldi, A., Berglund, L., Deflorian, F. and Pegoretti, A. (2015) A Comparison between Micro- and Nanocellulose-Filled Composite Adhesives for Oil Paintings Restoration. Nanocomposites, 1, 195-203. https://doi.org/10.1080/20550324.2015.1117239
[44]	Mahrdt, E., Pinkl, S., Schmidberger, C., van Herwijnen, H.W.G., Veigel, S. and Gindl-Altmutter, W. (2016) Effect of Addition of Microfibrillated Cellulose to Urea-Formaldehyde on Selected Adhesive Characteristics and Distribution in Particle Board. Cellulose, 23, 571-580. https://doi.org/10.1007/s10570-015-0818-5
[45]	Klemm, D., Heublein, B., Fink, H.P. and Bohn, A. (2005) Cellulose: Fascinating Biopolymer and Sustainable Raw Material. Angewandte Chemie International Edition, 44, 3358-3393. https://doi.org/10.1002/anie.200460587
[46]	Stenstad, P., Andresen, M., Tanem, B.S. and Stenius, P. (2008) Chemical Surface Modifications of Microfibrillated Cellulose. Cellulose, 15, 35-45. https://doi.org/10.1007/s10570-007-9143-y
[47]	Kalia, S., et al. (2011) Cellulose-Based Bio- and Nanocomposites: A Review. International Journal of Polymer Science, 2011, Article ID: 837875.
[48]	Moon, R.J., Martini, A., Nairn, J., Simonsen, J. and Youngblood, J. (2011) Cellulose Nanomaterials Review: Structure, Properties and Nanocomposites. Chemical Society Reviews, 40, 3941-3994. https://doi.org/10.1039/c0cs00108b
[49]	Islam, M.T., Alam, M.M., Patrucco, A., Montarsolo, A. and Zoccola, M. (2014) Preparation of Nanocellulose: A Review. AATCC Journal of Research, 1, 17-23. https://doi.org/10.14504/ajr.1.5.3
[50]	Ferreira, F.V., Mariano, M., Rabelo, S.C., Gouveia, R.F. and Lona, L.M.F. (2018) Isolation and Surface Modification of Cellulose Nanocrystals from Sugarcane Bagasse Waste: From a Micro- to a Nano-Scale View. Applied Surface Science, 436, 1113-1122. https://doi.org/10.1016/j.apsusc.2017.12.137
[51]	Grishkewich, N., Mohammed, N., Tang, J. and Tam, K.C. (2017) Recent Advances in the Application of Cellulose Nanocrystals. Current Opinion in Colloid & Interface Science, 29, 32-45. https://doi.org/10.1016/j.cocis.2017.01.005
[52]	Moon, R.J., Schueneman, G.T. and Simonsen, J. (2016) Overview of Cellulose Nanomaterials, Their Capabilities and Applications. Jom, 68, 2383-2394. https://doi.org/10.1007/s11837-016-2018-7
[53]	Mondal, S. (2017) Preparation, Properties and Applications of Nanocellulosic Materials. Carbohydrate Polymers, 163, 301-316. https://doi.org/10.1016/j.carbpol.2016.12.050
[54]	Mishra, R.K., Sabu, A. and Tiwari, S.K. (2018) Materials Chemistry and the Futurist Eco-Friendly Applications of Nanocellulose: Status and Prospect. Journal of Saudi Chemical Society, 22, 949-978. https://doi.org/10.1016/j.jscs.2018.02.005
[55]	Klemm, D., et al. (2018) Nanocellulose as a Natural Source for Groundbreaking Applications in Materials Science: Today’s State. Materials Today, 21, 720-748. https://doi.org/10.1016/j.mattod.2018.02.001
[56]	Mesquita, R.G.A., et al. (2018) Urea Formaldehyde and Cellulose Nanocrystals Adhesive: Studies Applied to Sugarcane Bagasse Particleboards. Journal of Polymers and the Environment, 26, 3040-3050. https://doi.org/10.1007/s10924-018-1189-4
[57]	Chen, H., Nair, S.S., Chauhan, P. and Yan, N. (2019) Lignin Containing Cellulose Nanofibril Application in pMDI Wood Adhesives for Drastically Improved Gap-Filling Properties with Robust Bondline Interfaces. Chemical Engineering Journal, 360, 393-401. https://doi.org/10.1016/j.cej.2018.11.222
[58]	Tayeb, A.H., Amini, E., Ghasemi, S. and Tajvidi, M. (2018) Cellulose Nanomaterials-Binding Properties and Applications: A Review. Molecules, 23, 2684. https://doi.org/10.3390/molecules23102684
[59]	Lee, K.Y., Aitomäki, Y., Berglund, L.A., Oksman, K. and Bismarck, A. (2014) On the Use of Nanocellulose as Reinforcement in Polymer Matrix Composites. Composites Science and Technology, 105, 15-27. https://doi.org/10.1016/j.compscitech.2014.08.032
[60]	Habibi, Y. (2014) Key Advances in the Chemical Modification of Nanocelluloses. Chemical Society Reviews, 43, 1519-1542. https://doi.org/10.1039/C3CS60204D
[61]	Khattab, M.M., Abdel-Hady, N.A. and Dahman, Y. (2017) Cellulose Nanocomposites: Opportunities, Challenges, and Applications. Elsevier, Amsterdam. https://doi.org/10.1016/B978-0-08-100957-4.00021-8
[62]	Klemm, D., et al. (2011) Nanocelluloses: A New Family of Nature-Based Materials. Angewandte Chemie International Edition, 50, 5438-5466. https://doi.org/10.1002/anie.201001273
[63]	Kajtna, J. and Sebenik, U. (2017) Novel Acrylic/Nanocellulose Microsphere with Improved Adhesive Properties. International Journal of Adhesion and Adhesives, 74, 100-106. https://doi.org/10.1016/j.ijadhadh.2016.11.013
[64]	Dastjerdi, Z., Cranston, E.D. and Dubé, M.A. (2018) Pressure Sensitive Adhesive Property Modification Using Cellulose Nanocrystals. International Journal of Adhesion and Adhesives, 81, 36-42. https://doi.org/10.1016/j.ijadhadh.2017.11.009
[65]	Hamed, S.A.A.K.M. and Hassan, M.L. (2019) A New Mixture of Hydroxypropyl Cellulose and Nanocellulose for Wood Consolidation. Journal of Cultural Heritage, 35, 140-144. https://doi.org/10.1016/j.culher.2018.07.001
[66]	Lengowski, E.C., Bonfatti Júnior, E.A., Nishidate Kumode, M.M., Carneiro, M.E. and Satyanarayana, K.G. (2019) Nanocellulose-Reinforced Adhesives for Wood-Based Panels. In: Inamuddin, Thomas, S., Kumar Mishra, R. and Asiri, A.M., Eds., Sustainable Polymer Composites and Nanocomposites, No. 167, Springer, Berlin, 1001-1025. https://doi.org/10.1007/978-3-030-05399-4_35
[67]	Jiang, W., Haapala, A., Tomppo, L., Pakarinen, T., Sirviö, J.A. and Liimatainen, H. (2018) Effect of Cellulose Nanofibrils on the Bond Strength of Polyvinyl Acetate and Starch Adhesives for Wood. BioResources, 13, 2283-2292. https://doi.org/10.15376/biores.13.2.2283-2292
[68]	Veigel, S., Rathke, J., Weigl, M. and Gindl-Altmutter, W. (2012) Particle Board and Oriented Strand Board Prepared with Nanocellulose-Reinforced Adhesive. Journal of Nanomaterials, 2012, Article ID: 158503. https://doi.org/10.1155/2012/158503
[69]	Tajvidi, M., Gardner, D.J. and Bousfield, D.W. (2016) Cellulose Nanomaterials as Binders: Laminate and Particulate Systems. Journal of Renewable Materials, 4, 365-376. https://doi.org/10.7569/JRM.2016.634103
[70]	Kojima, Y., et al. (2013) Binding Effect of Cellulose Nanofibers in Wood Flour Board. Journal of Wood Science, 59, 396-401. https://doi.org/10.1007/s10086-013-1348-0
[71]	Jeong, S.S., Böckenfeld, N., Balducci, A., Winter, M. and Passerini, S. (2012) Natural Cellulose as Binder for Lithium Battery Electrodes. Journal of Power Sources, 199, 331-335. https://doi.org/10.1016/j.jpowsour.2011.09.102
[72]	Nirmale, T.C., Kale, B.B. and Varma, A.J. (2017) A Review on Cellulose and Lignin Based Binders and Electrodes: Small Steps towards a Sustainable Lithium Ion Battery. International Journal of Biological Macromolecules, 103, 1032-1043. https://doi.org/10.1016/j.ijbiomac.2017.05.155
[73]	Lu, H., Behm, M., Leijonmarck, S., Lindbergh, G. and Cornell, A. (2016) Flexible Paper Electrodes for Li-Ion Batteries Using Low Amount of TEMPO-Oxidized Cellulose Nanofibrils as Binder. ACS Applied Materials & Interfaces, 8, 18097-18106. https://doi.org/10.1021/acsami.6b05016
[74]	Lavoine, N., Desloges, I., Dufresne, A. and Bras, J. (2012) Microfibrillated Cellulose—Its Barrier Properties and Applications in Cellulosic Materials: A Review. Carbohydrate Polymers, 90, 735-764. https://doi.org/10.1016/j.carbpol.2012.05.026
[75]	Tyagi, P., Lucia, L.A., Hubbe, M.A. and Pal, L. (2019) Nanocellulose-Based Multilayer Barrier Coatings for Gas, Oil, and Grease Resistance. Carbohydrate Polymers, 206, 281-288. https://doi.org/10.1016/j.carbpol.2018.10.114
[76]	Liu, A., Walther, A., Ikkala, O., Belova, L. and Berglund, L.A. (2011) Clay Nanopaper with Tough Cellulose Nanofiber Matrix for Fire Retardancy and Gas Barrier Functions. Biomacromolecules, 12, 633-641. https://doi.org/10.1021/bm101296z
[77]	Liu, C., et al. (2017) Properties of Nanocelluloses and Their Application as Rheology Modifier in Paper Coating. Industrial & Engineering Chemistry Research, 56, 8264-8273. https://doi.org/10.1021/acs.iecr.7b01804
[78]	Cai, Z. and Niska, K.O. (2012) Nanocelluloses: Potential Materials for Advanced Forest Products Proceedings of Nanotechnology in Wood Composites Symposium.
[79]	Damásio, R., Carvalho, A., Gomes, F., Carneiro, A., Ferreira, J. and Colodette, J. (2017) Interação de nanocristais de celulose com o adesivo ureia-formaldeído em juntas coladas de Eucalyptus sp. Effect of CNC Interaction with Urea-Formaldehyde Adhesive in Bonded Joints of Eucalyptus sp. Interação, 45, 169-176. https://doi.org/10.18671/scifor.v45n113.17
[80]	Amini, E., Tajvidi, M., Gardner, D.J. and Bousfield, D.W. (2017) Utilization of Cellulose Nanofibrils as a Binder for Particleboard Manufacture. BioResources, 12, 4093-4110. https://doi.org/10.15376/biores.12.2.4093-4110
[81]	Cui, J., et al. (2015) Enhancement of Mechanical Strength of Particleboard Using Environmentally Friendly Pine (Pinus pinaster L.) Tannin Adhesives with Cellulose Nanofibers. Annals of Forest Science, 72, 27-32. https://doi.org/10.1007/s13595-014-0392-2
[82]	Kojima, Y., et al. (2016) Reinforcement of Fiberboard Containing Lingo-Cellulose Nanofiber Made from Wood Fibers. Journal of Wood Science, 62, 518-525. https://doi.org/10.1007/s10086-016-1582-3
[83]	Zhang, H., Zhang, J., Song, S.P., Wu, G.F. and Pu, J.W. (2011) Modified Nanocrystalline Cellulose from Two Kinds Emission and Bonding Strength of Urea-Fromaldehyde Resin Adhesive. Materials Science, 6, 4430-4438.
[84]	Gao, Q., Li, J., Shi, S.Q., Liang, K. and Zhang, X. (2012) Soybean Meal-Based Adhesive Reinforced with Cellulose Nano-Whiskers. BioResources, 7, 5622-5633. https://doi.org/10.15376/biores.7.4.5622-5633
[85]	Ayrilmis, N., Lee, Y.K., Kwon, J.H., Han, T.H. and Kim, H.J. (2016) Formaldehyde Emission and VOCs from LVLs Produced with Three Grades of Urea-Formaldehyde Resin Modified with Nanocellulose. Building and Environment, 97, 82-87. https://doi.org/10.1016/j.buildenv.2015.12.009
[86]	Via, B.K., Fasina, O. and Atta-Obeng, E. (2012) Effect of Microcrystalline Cellulose, Species, and Particle Size on Mechanical and Physical Properties of Particleboard. Wood and Fiber Science, 44, 227-235.
[87]	Hunt, J.F., Leng, W. and Tajvidi, M. (2017) Vertical Density Profile and Internal Bond Strength of Wet-Formed Particleboard Bonded with Cellulose Nanofibrils. Wood and Fiber Science, 49, 413-423.
[88]	Diop, C.I.K., Tajvidi, M., Bilodeau, M.A., Bousfield, D.W. and Hunt, J.F. (2017) Evaluation of the Incorporation of Lignocellulose Nanofibrils as Sustainable Adhesive Replacement in Medium Density Fiberboards. Industrial Crops and Products, 109, 27-36. https://doi.org/10.1016/j.indcrop.2017.08.004
[89]	Cheng, H.N., Kilgore, K., Ford, C., Fortier, C., Dowd, M.K. and He, Z. (2019) Cottonseed Protein-Based Wood Adhesive Reinforced with Nanocellulose. Journal of Adhesion Science and Technology, 33, 1357-1368. https://doi.org/10.1080/01694243.2019.1596650
[90]	Örs, Y., Atar, M. and Özçifçi, A. (2000) Bonding Strength of Poly(vinyl acetate)-Based Adhesives in Some Wood Materials Treated with Impregnation. Journal of Applied Polymer Science, 76, 1472-1479. https://doi.org/10.1002/(SICI)1097-4628(20000531)76:9<1472::AID-APP11>3.0.CO;2-O
[91]	Qiao, L., et al. (2011) Improvement of the Water Resistance of Poly(vinyl acetate) Emulsion Wood Adhesive. Pigment and Resin Technology, 29, 152-158. https://doi.org/10.1108/03699420010334303
[92]	Qiao, L. and Easteal, A.J. (2001) Aspects of the Performance of PVAc Adhesives in Wood Joints. Pigment & Resin Technology, 30, 79-87. https://doi.org/10.1108/03699420110381599
[93]	Kaboorani, A. and Riedl, B. (2011) Improving Performance of Polyvinyl Acetate (PVA) as a Binder for Wood by Combination with Melamine Based Adhesives. International Journal of Adhesion and Adhesives, 31, 605-611. https://doi.org/10.1016/j.ijadhadh.2011.06.007
[94]	Chaabouni, O. and Boufi, S. (2017) Cellulose Nanofibrils/Polyvinyl Acetate Nanocomposite Adhesives with Improved Mechanical Properties. Carbohydrate Polymers, 156, 64-70. https://doi.org/10.1016/j.carbpol.2016.09.016
[95]	Gadhave, R.V., Mahanwar, P.A. and Gadekar, P.T. (2019) Study of Cross-Linking between Boric Acid and Different Types of Polyvinyl Alcohol Adhesive. Open Journal of Polymer Chemistry, 9, 16-26. https://doi.org/10.4236/ojpchem.2019.91002