Preparation of uniform and porous polyurea microspheres of large size through interfacial polymerization of toluene diisocyanate in water solution of ethylene diamine

Uniform and porous polyurea (PU) microspheres of large size, with the diameter between 400 gm and 750 mu m, are prepared through interface polymerization by drop-wise addition of toluene diisocyanate (TDI) to an aqueous solution of ethylene diamine (EDA). TDI addition is done through a needle with pore size of 60 mu m or larger at constant rate associated with the needle pore size. Effects of the needle pore size for TDI addition, EDA concentration in water and polymerization temperature on the formation of the PU spheres are studied. Results indicate that PU spheres are obtained with varied needle pore size. However, highly uniform PU spheres are achieved only with the needle pore size of 180 gm or larger. In order to get uniform microspheres, polymerization should be carried out at 60-65 degrees C with EDA/TDI molar ratio kept at 2/21-4/21. Out of these limits, the uniformity of the polymer spheres is deteriorated. Morphology of the microspheres is examined under scanning electron microscope, which shows that the microspheres are consisting of a coarse shell and a core with macroporous structure. The mechanism of the polymerization and PU sphere formation are discussed. (C) 2016 Elsevier B.V. All rights reserved.