Modified Achira (Canna edulis) starch-based adhesives: effect of acid hydrolysis and urea derivatization on physicochemical properties

In recent decades, due to high market demand and multiple environmental concerns, attention has been focused on the use of starch as renewable raw material for adhesives elaboration. Particularly, the origin and film-forming properties of Achira (Canna edulis) starch make it a potential representative for the development of bioadhesives. In this study, achira starch modified by acid hydrolysis and subsequent derivatization with urea was used to prepare adhesives for plywood substrates. For this purpose, the modified starch and polyvinyl alcohol (PVA) were used to prepare several formulations with different proportions of components. Afterwards, they were characterized in terms of physicochemical and mechanical properties. The formation of starch carbamates was confirmed not only by the results of nitrogen content, but also by infrared spectroscopy through the presence of N-H and C=O groups. On the other hand, viscosity increased with PVA content due to the interaction of hydroxyl groups, while starch had the opposite effect. Shear strength showed higher values at higher concentrations of PVA and starch. From the perspective of mechanical behavior, the results showed similarities with a commercial adhesive based on polyvinyl acetate (PVAc), as well as with other bio-based adhesives from studies conducted under comparable conditions.