Synthesis, characterization, and application of starch-based adhesives modified with itaconic acid and N-hydroxyethyl acrylamide

Abstract

A renewable, biodegradable, formaldehyde-free starch-based adhesive was prepared by grafting itaconic acid (IA) and N-hydroxyethyl acrylamide (HEAA) onto corn starch. The adhesive exhibits excellent performance for particleboard and low viscosity (251 mPas, 62 s measured by flow cup viscometer) using 8% addition of IA (w/w, dry starch basis), and 10% addition of HEAA (w/w, dry starch basis). The thickness swelling of the particleboard was decreased to 10%. When unmodified starch-based adhesive was used, the particleboard soaked in water disintegrated completely. The data obtained from the Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), confocal Raman microscopy (CRM), and 13C cross-polarization magic-angle spinning (CPMAS) showed that IA wrapped and covered the surface of starch granules. HEAA is unevenly distributed on the surface of starch as a cross-linked backbone. After the hot-pressing process, IA and HEAA are self-cross-linked and inter-cross-linked, respectively, to form a complex network structure, which can inhibit the disintegration caused by excessive expansion during the soaking process of the board, thus improving the water resistance of the starch adhesive.