Development of Sustainable Adhesives Based on Polysaccharide-Polyelectrolyte Complexes for Natural Fiber-Based Materials

Polysaccharide-polyelectrolyte complex (PPC) materials have been recently explored as barrier materials for packaging applications. No studies, however, have been found on PPC adhesives developed for use in paperboard and wood composites. In this study, we prepared carboxymethyl cellulose (CMC)/chitosan (CS)-based PPCs (CMS PPCs) via ball milling and characterized their water and thermal stability, as well as adhesion performance, using both paper and wood substrates. The water stability of CMS PPC was examined using water solubility and water swelling tests. Preparation pH (4.5, 5.5, and 6.5) of CMS dominated the dissolution of CS and influenced complexation. Thus, the highest swelling rate and solubility occurred at CMS prepared at pH 6.5, which led to the lowest CS dissolution and weakest complexation. Comparison among solid contents (6, 7.5, and 9%) showed that the larger particle size associated with 6% CMS resulted in a looser film structure and poorer water stability. Adhesion performance with paper substrates indicated that an adhesive loading of 10 g/m² was needed for optimal bonding strength. Nine percent of CMS prepared with pH 4.5 exhibited a wood bonding strength of 7.89 ± 0.83 MPa in the dry state and retained approximately 35% strength in the wet state.