Synthesis of isocyanate microcapsules as functional crosslinking agent for wood adhesive

Abstract

ABSTRACT In this study, controlled-release isocyanate microcapsules were synthesized as functional crosslinking to slowdown the rate of cross-linking reactions. The isocyanate microcapsules were prepared by In-situ polymerization with polymethylene polyphenyl polyisocyanates (PAPI) as core and Urea formaldehyde resin as shell in oil-in-water emulsions. The particle size distribution, chemical structure, morphology, activity, and stability of the microcapsules were comprehensively characterized. Finally, the microcapsules were applied in a wood adhesive to prepare water-resistant plywood. The results showed that the size of the microcapsules was around 100 μm, the active content of NCO was about 23.5%, and the core content was approximately 80%. Compared with the stability of the bulk isocyanate, the stability of the isocyanate in microcapsules was significantly improved in the wood adhesive system. Furthermore, the isocyanate microcapsules showed highly efficient in plywood at different time, which indicated that isocyanate microcapsules could be controllable released in plywood applications.