Self-Neutralizing\nCitric Acid–Corn Starch Wood\nAdhesives

Very acidic pHs are not allowed in wood adhesives. The\ndevelopment\nof new self-neutralizing adhesives has therefore become a priority.\nThe corn starch–citric acid adhesive (CACS) was developed recently\nto be an environmentally friendly biomass adhesive. In this work,\nwe propose to prepare self-neutralizing corn starch adhesives using\nthe CACS adhesive as the matrix and morpholine/maleic acid (MM) and\nmorpholine/d-lactic acid (DM) as the neutralizing agents.\nThe results showed that the MM neutralizing additive is more effective\nthan the DM in eliminating the residual acid on the glue line. When\nthe addition of the MM neutralizer was 10%, the pH of the adhesive\nsystem increased to about 4.5 and an adhesive with stable water resistance,\ngood durability, and high bonding strength and durability acceptable\nto the relevant standards could be maintained. Structural analysis\nproved that MA was also involved in the esterification reaction of\ncorn starch (CS). Therefore, the MM-CACS adhesive developed in this\nstudy has the potential to replace traditional petroleum-based adhesives\nas a new type of biomass self-neutralizing adhesive.