Preparation and characterization of large-size halloysite nanotubes particles by a combined technique of interfacial polymerization and condensation polymerization

To granulate halloysite nanotubes (HNTs) into large-size particles, interfacial polymerization and condensation polymerization were combined. The former was used to form surface layer of particles and the latter was used to improve particle strength. Polyethylenimine (PEI) and terephthaloyl chloride were chosen, respectively as hydrophilic monomer and hydrophobic monomer in interfacial polymerization. Condensation polymerization was carried out between PEI and glycerol polyglycidyl ether (GPE). The results show that HNTs particles have sphere shape and its diameters range from 1.7 to 2.5 mm and vary with preparation condition. SEM images show that particles have typical core-shell structure with dense surface layer and porous inner structure and single nanotube is completely encapsulated by polymer material. The characterization of BET shows that because of dense surface layer and encapsulation of nanotubes, the specific surface area of particles determined decreases dramatically.