Effect of HCl on Starch Structure and Properties of Starch-based Wood Adhesives

Starch-based adhesive was prepared from corn starch and polyvinyl alcohol (PVA) as raw materials by acid hydrolysis with HCl. The starch was hydrolyzed with different amounts of HCl and characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermal gravimetric analysis. The results indicated that different amounts of HCl affected hydrogen bonds, the amount of free hydroxyl groups, crystalline structure, compatibility between starch and PVA, thermal stability, and bond strength. The crystallinity decreased by 13.7% when the amount of acid was 33% compared with untreated starch. The bond strength reached its maximum of 1.35 MPa when the acid content was 23%. The initial decomposition temperature of starch decreased after acid hydrolysis. It was also noted that corrosion of the starch surface increased with increasing acid content.