Chemical Modification of Nanocellulose in Wood Adhesive: Review

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.