Water-dispersible isocyanate modified using plant-based castor oil: Synthesis and application as crosslinking agent

To improve the performance of waterborne materials, this study attempts to prepare a novel water-dispersible isocyanate crosslinking agent based on plant-based castor oil. The intermediate maleated castor oil and water-dispersible isocyanates with different R values [n(NCO)/n(OH)] are prepared and characterized by FTIR and 1 H NMR. The viscosity test, isocyanate content titration, particle size analysis, and the morphologies indicate that the optimal condition for the water-dispersible isocyanates (e.g., best storage stability and particle size distribution) is at R value = 40. The mechanical test proves that the water-dispersible isocyanates can greatly improve the bonding strength and water resistance of wood adhesives, showing an increase of wet strength to be as high as 146 % and 506 % for urea-formaldehyde resin and white latex, respectively. The castor oil-mediated water-dispersible isocyanate system opens a novel avenue to synthesize waterborne crosslinking agent for applications in adhesives, coatings, and structural materials.