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

[Display omitted] • Water-dispersible isocyanates based on castor oil were prepared for the first time. • Dispersion performance is related to the number of hydrophilic groups and viscosity. • The bonding strength was obviously improved when applied to water-based adhesives. • Suitable for various water-based adhesives when used as crosslinking agents. 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 1H 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. [ABSTRACT FROM AUTHOR]