Chemical Modification of Nanocellulose in Wood Adhesive: Review

Abstract

Bio-based nanomaterial is more attractive, due to its abundance, eco-friendliness and sustainability, when compared to the non-renewable toxic petrochemicals used in the wood adhesive sector. Recent studies on the formaldehyde emission by petrochemical binders in wood adhesives have attracted scientists for the research in biomaterial-based binders. In this aspect nanocellulose (NC) is one such material which has reinforcing ability and has natural binding properties. Conventional wood adhesive uses petrochemical-based binders and additives. Inclusion of nanocellulose in wood adhesive could drastically reduce the dependency on non-renewable petroleum sources. Even though wood adhesive uses NC for improving mechanical properties of the adhesive, usage is restricted because of its inability to enhance tackiness and adhesion compared with petrochemicals. Availability of free hydroxyl groups and feasibility for modification can be a potential way for functionalization of this nanomaterial. To improve adhesion properties and to make nanocellulose act as a functional filler, the crosslinking approach can be a possible solution. Enhancement of thermal properties with improved thermal degradation, water barrier properties of crosslinked films and enhanced mechanical properties especially in crosslinked poly (vinyl alcohol) (PVA) matrix, which is one of the binders for wood adhesive discussed in this review paper proves the potential applicability of crosslinked NC. Hence by inclusion of NC in wood adhesive and crosslinking with the binder, both mechanical and performance properties are expected to enhance which will create a new world and possibilities for the bio-based eco-friendly wood adhesives. In this review paper, we have reviewed the crosslinking of nanocellulose to enhance the performance of wood adhesives.

Nanocellulose: From Fundamentals to Advanced Applications

“…There are few reports which studied on the application of nanocellulose in wood adhesives (Lengowski et al, 2019;Vineeth et al, 2019). Commonly, wood adhesives can be classified into two big groups, which are soft and brittle adhesive.…”

“…Kwon et al, 2015 MFC Up to 5 UF The addition of MFC indicated lower thermal stability at different F/U mol ratio except the enhancement of thermal stability at low F/U mol ratio which is 0.9 (E0). Nuryawan et al, 2017 (vinyl alcohol) may increase the performance and mechanical features, opening new possibilities for eco-friendly and bio-based wood adhesives (Vineeth et al, 2019). These achievements can reduce the dependency of petrochemicals in wood adhesives field in the near future.…”

“…The benefit of cellulose can be further extended when cellulose chains are bundled together, generating highly ordered regions that can be subsequently isolated as nano-particles, known as cellulose nanomaterials or nanocelluloses, considered as useful class of futuristic materials (Foster et al, 2018) owing to their physicochemical features. In addition to be renewable and abundant, they combine chemical inertness, excellent stiffness, high strength, low coefficient of thermal expansion, low density, dimensional stability, and ability to modify its surface chemistry (Phanthong et al, 2018;Rajinipriya et al, 2018;Naz et al, 2019;Vineeth et al, 2019;Köse et al, 2020).…”

Cellulose Nanocrystals/Graphene Hybrids—A Promising New Class of Materials for Advanced Applications

“…Conceptually, NC can be produced by a top-down hydrolysis methodology through different steps, that is, (i) pretreatment processes of lignocellulosic biomass employing physical approaches concerning crushing, screening, washing and cooking to eliminate coarse particles, oily content and dust from the material surface, (ii) removing extractive/hemicellulose/lignin via chemical, physical, physicochemical, biological or the combination of two or more treatments, (iii) fragmentation and cleavage of cellulosic elementary fibrils or micro-fibrils to generate nanofibers through various approaches and (iv) post-treatments such as solvent removing, dialysis, sonication, centrifugation, surface modification, stabilization and drying. The three latter steps have received great interest from the scientific community for designing products with desired features [ 12 , 13 , 23 , 27 , 38 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ]. NC possesses excellent useful properties such as renewability, eco-friendliness, biocompatibility, non-toxicity, hydrogen-bonding capacity, tunable crystallinity, high chemical resistance, tailored aspect ratios (100–150), low thermal expansion coefficient, reactive surface, low density (1.6 g/cm 3 ), high specific surface area (100–200 of m 2 /g), high tensile strength (7.5–7.7 GPa) and elastic modulus (130–150 GPa) [ 10 , 30 ].…”

Comparative study on the properties of cross‐linked cellulose nanocrystals/chitosan film composites with conventional heating and microwave curing

“…This could be attributed to the cross-linking reaction between CNC and GA via hydrogen bonding. [25][26][27] Besides, the crosslinking reaction between chitosan and glutaraldehyde could increase the activation energy due to the reduced chain mobility of cross-linked network and hence, higher amount of energy was required for cross-linking of the reactants. [28] Similar finding was reported by Correia et al [29] in which the activation energy was increased for cross-linked samples.…”