Environment-friendly urea-oxidized starch adhesive with zero formaldehyde-emission.

This study reports on an environment-friendly renewable and zero formaldehyde-emission urea-oxidized starch (U-OSt) adhesive based on native corn starch. The adhesive was prepared by polycondensation reaction of oxidized starch and urea. The morphology, molecular structure, crystalline structure, shear strength and viscosity of the adhesive, the native and oxidized starch were instrumentally investigated. The influence of processing factors was studied, such as the oxidizer content, the urea content and the addition of titanium dioxide nanoparticle (nano-TiO2). The results show the adhesive has an excellent comprehensive performance at urea content of 50% (w/w, dry starch basis) while 5.0% (w/w, dry starch basis) KMnO4 as oxidizer. The dry shear strength was increased by 16.9% by adding of nano-TiO2 content of 1.5% (w/w, dry starch basis), and the corresponding viscosity was 4100mPas. It is found appropriate amount of nano-TiO2 played a complementary effect between adhesive and adherend, which enhanced the adhesive property and stability of adhesive.