Preparation and stability of reverse PAPI emulsion adhesive stabilized by chitin

Isocyanate adhesive has the advantages of excellent bonding performance and wide range of substrate adaptation, and is suitable for wood green processing. Aiming at the common scientific problems of short application period and unstable bonding properties caused by easy reaction of isocyanate adhesive with active hydrogen-containing substances, this study prepared reverse PAPI emulsion by reacting chitin nanoparticles with polymethylene polyphenyl polyisocyanate (PAPI) with Pickering emulsion system. A barrier was constructed between water molecules and PAPI to prevent their mutual diffusion, and the rapid reaction between water and isocyanate group was retarded in situ to prepare reverse isocyanate Pickering emulsion with long application period. In this paper, the effects of different kinds and mass fractions of chitin nanoparticles on the stability, viscosity, thermal stability and bonding properties of reverse PAPI emulsion adhesive were discussed. The results show that the properties of the reverse PAPI emulsion with chitin nanoparticles are enhanced to some extent compared with the emulsion without stabilizer. Compared with PAPI, the viscosity of reverse emulsions is significantly improved, which greatly improves the percolation problem caused by the low initial viscosity of PAPI. Moreover, the prepared reverse PAPI emulsions have a long application period and are suitable for large format continuous bonding of wood materials.