Preparation of isocyanate microcapsules by complex coacervation and its application in plywood

ABSTRACTAt present, the use of isocyanate adhesives mostly requires the assistance of solvents, which can cause adverse environmental pollution and health effects. The aqueous isocyanate avoids the shortcomings of the solvent, but shortens the working life of the isocyanate. Isocyanate microcapsules can avoid these shortcomings, and can also solidify isocyanate to improve the efficiency of isocyanate use. In this study, microencapsulation technology was used to protect the highly reactive -NCO group, improve the stability of isocyanate, and prolong the working life of isocyanate in water-based wood adhesives. That is, isocyanate microcapsules with gum Arabic/gelatin as shell and isocyanate as core were prepared in oil-in-water emulsion by complex coacervation. In addition, the preparation process was optimized by changing the parameters. Then, the prepared isocyanate microcapsules were characterized and analyzed by Fourier transform infrared spectrometer, Scanning electron microscope, Particle size analyzer, etc. Finally, plywood was prepared by using the prepared isocyanate microcapsules in the wood adhesive. The results showed that, the particle size of isocyanate microcapsules was controllable, and the content of active groups and core in the prepared isocyanate microcapsules can reach a high level. The isocyanate microcapsules extend the working life of isocyanates from about 30 mins to 5 hours, and significantly improve the stability of isocyanates. The bonding strength of the prepared plywood meets the requirements of (Class I plywood) with only 20% -NCO addition.KEYWORDS: Isocyanate microcapsulescomplex coacervationplywoodworking life AcknowledgmentThis work was supported by the Educational Commission of Henan Province of China (No. 23A430038) and the National Forestry and Grassland Administration Key Laboratory of Plant Fiber Functional Materials (2022KFJJ12). Special thanks to the support of Doctoral Cultivation Fund Project of Henan University of Engineering (No. D2022003).Disclosure statementNo potential conflict of interest was reported by the author(s).Authorship contribution statementYangbao Ma, Changhui Liu and Yanhua Zhang conceived and designed the experiments; Yangbao Ma, Xiaohui Chang, Ao Liu, Xiaona Meng performed the experiments; Yangbao Ma, Changhui Liu, Tao Wang and Yanhua Zhang analyzed the data; Yangbao Ma contributed reagents/materials/analysis tools; Yangbao Ma and Changhui Liu wrote the paper. All authors read and approved the manuscripts.Additional informationFundingThe work was supported by the National Natural Science Foundation of China [32071692]; National Forestry and Grassland Administration Key Laboratory of Plant Fiber Functional Materials [2022KFJJ12]; Educational Commission of Henan Province of China [23A430038].