Preparation of isocyanate microcapsules by interfacial polymerization/in-situ polymerization and their application in wood adhesives

Isocyanate has excessively high chemical activity because of its highly unsaturated isocyanate group (-NCO), which limits its application. In this paper, isocyanate microcapsules with polyurea/urea-formaldehyde resin were prepared by interfacial polymerization/in-situ polymerization, and the degree of interfacial polymerization was controlled by interfacial polymerization time, and explored its effect on the stability of microcapsules. The results showed that the isocyanate microcapsules prepared by in-situ polymerization after 90 min of interfacial polymerization have the best stability. The microcapsules were orange-yellow spheres with liquid in the inner and owned about 25% active group with the particle size of about 200 µm. It also had service stability and thermal stability. Finally, the prepared isocyanate microcapsules were used as crosslinking agent in wood adhesives. The reaction between isocyanate and active hydrogen (water) in the adhesives system was delayed by the shielding effect of the microcapsules wall, the work life of isocyanate was increased, and the stability of the isocyanate was improved in the adhesives. The liquid core was released by pressure to produce efficient chemical crosslinking to improve the bonding strength and water resistance of plywood.