Preparation of isocyanate microcapsules as functional crosslinking agent by minimalist interfacial polymerization

Abstract

Isocyanate is an extremely high activity compound that has been extensively used in the chemical materials. In this study, we employ microcapsules in preserving the activity of isocyanates and controlling their release in wood adhesives for plywood. Isocyanate microcapsules were synthesized by a one-step interfacial polymerization in an oil-in-water (O/W) emulsion. The particle size distribution, chemical structure, morphology, activity and stability of the obtained isocyanate microcapsules were characterized by laser particle size analyzer, n-dibutylamine titration, FTIR, SEM, and a universal strength testing machine. The as-synthesized microcapsules had approximately 25% active –NCO group and the core accounted for 77% of the total weight. The isocyanate microcapsules demonstrated satisfactory stability by preserving majority of the active –NCO group and core weight during 180 days of storage. These isocyanate microcapsules were used as functional crosslinking agent for making plywood. The resultant plywood showed higher tensile shear strength than the strength mandated in the Chinese National Standard (GB/T 9846-2015). Furthermore, the wet strength was greatly improved to meet the Class I and II plywood standards. Additionally, the stability of isocyanate microcapsules in wood adhesives were significantly enhanced for a prolonged application time. Their excellent bonding properties and stability make isocyanate microcapsules an ideal additive for use in chemical and manufacturing materials.