Reinforcement of interfacial and bonding strength of soybean meal-based adhesive via kenaf fiber-CaCO3 anchored N-cyclohexyl-2-benzothiazole sulfenamide

The development of soybean meal-based adhesive is currently hindered by its weak bonding strength and poor water resistance. This study aims to develop a natural fiber-reinforced soybean meal adhesive with enhanced water resistance and bonding strength. To improve the interfacial interaction between the matrix and kenaf fiber (KF), the fiber was modified using a two-step process, (1) KF was treated with calcium carbonate (TKF) via an inorganic nanoparticle impregnation (INI) process; and (2) N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was chemically bonded onto TKF to obtain the functionalized fiber (TKF-s-CZ). The bonded CZ molecules on TKF were found to have stronger interfacial interaction between TKF-s-CZ and the matrix, accelerating the cross linking reaction. The resultant PSM/TKF-s-CZ adhesive exhibited higher bonding strength and water-resistance than the control one. Compared to the control one, the wet shear strength of the PSM/TKF-s-CZ adhesive increased from 0.38 MPa to 1.64 MPa, counting for an increase of 331.57%. The moisture uptake was reduced to 8.75% (10.76% of the PSM/TKF adhesive). This work also provides a new design strategy for the surface modification of filler and prepares a renewable, value-added soybean meal-based adhesive, which could play an important role in expanding the industrialized applications of these adhesives.