Abstract
A chemical modification by grafting alkyl chains using an octanal (C8) on chitosan was conducted with the aim to improve its water resistance for bonding applications. The chemical structure of the modified polymers was determined by NMR analyses revealing two alkylation degrees (10 and 15%). In this study, the flow properties of alkyl-chitosans were also evaluated. An increase in the viscosity was observed in alkyl-chitosan solutions compared with solutions of the same concentration based on native chitosan. Moreover, the evaluation of the adhesive strength (bond strength and shear stress) of both native and alkyl-chitosans was performed on two different double-lap adherends (aluminum and wood). Alkyl-chitosans (10 and 15%) maintain sufficient adhesive properties on wood and exhibit better water resistance compared to native chitosan.
Highlights
Available synthetic adhesives are mostly derived from depleting petrochemical resources
1 H-NMR analyses, the formulation of the adhesives based on alkyl-chitosans, and the assessment of their flow and adhesive properties to, the determination of their water resistance
The 1 H-NMR spectra (Figure 1) of N-alkyl-chitosan display characteristic peaks in the 1.7–0.9 ppm region, attributed to the protons of the methyl (-CH3 ) and methylene (-CH2 -) groups grafted onto the chitosan chain, which supports the chemical modification of chitosan
Summary
Available synthetic adhesives are mostly derived from depleting petrochemical resources. They present many advantages, such as high bond strength and water resistance [1]. Most of them are composed of volatile organic compounds or other toxic compounds, which are very dangerous for health and environment, such as epichlorohydrin and formaldehyde [2,3]. The need for environmentally friendly and healthy adhesives represents a real challenge and pushes wood industries and academics to develop alternatives to synthetic adhesives. Among bio-based molecules/polymers which can provide those characteristics, polysaccharides are interesting candidates. Their numerous hydroxyl groups can interact with numerous chemical functions and their high molecular weight can provide cohesive strength to materials
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