Calcium Carbonate Particles As Template To Prepare Polyurea Hollow Microspheres

With the advancement of technology, great progress has been achieved in polymer science. New polymer materials with high performance are urgently needed, which bring about new technologies in polymer manufacturing, particularly for polymer materials with specific structure, morphology and functionality. Hollow polymer microspheres are polymer material with hollow structure, which gives specific properties such as low density, high specific surface area, and they can be used to accommodate other guest molecules, etc. Hollow polymer microspheres are widely used in catalysis, coatings, cosmetics, biomedicine and other fields. Up to now, different techniques have been developed to prepare hollow microspheres, including templating, self-assembly, emulsion Polymerization, etc. Among these techniques, template method is the easiest and most widely used due to easy control for the morphology and the size of the hollow microspheres.Polyurea, a type of new polymer materials with specific functionality, has been known for its excellent performance, simple preparation and is widely used in different applications. Rapid development and great interests have been seen worldwide. In an earlier work, precipitation polymerization of isophorone diisocyanate(IPDI) as the only monomer was carried out in our Lab using water/acetone as the solvent without any other additives. Highly uniform microspheres with neat surface bearing abundant amine groups were prepared. As a continuation of the work, we selected IPDI as the only monomer, calcium carbonate particles as template to prepare CaCO3/polyurea core/shell composite microspheres using water/acetone as the solvent. And then polyurea hollow microspheres were obtained by dissolution of the CaCO3 core by immersing in hydrochloric acid solution.This work discusses the influence of different experimental conditions on the preparation and the formation mechanism of CaCO3 particles and the polyurea hollow microspheres. First of all, CaCO3 microsphere particles were prepared through the reaction between Na2CO3 and CaCl2, using PSS as crystal growth inhibitors. The results indicate that, the diameter of prepared CaCO3 was 3.2 μm at 15 °C. In the second part of the work, CaCO3/polyurea core/shell composite particles were prepared by precipitation polymerization of IPDI as the only monomer in water/acetone as the solvent using CaCO3 microsphere particles as the template. Polyurea hollow microspheres were obtained by immersing the core/shell composite microspheres in hydrochloric acid solution. The results showed that, the size of polyurea hollow microspheres particles were dependent on the size of the template. The volume of the hollow cavity was in accordance with the size of the templates. The size of polyurea hollow microspheres particles were uniform when the weight ratio of water/acetone was 30/70 and oscillation dispersion frequency was at 120 osc/min. The shell thickness of hollow microspheres can be adjusted by changing monomer amount used and reaction temperature. The shell thickness of the hollow microspheres increased with the increased amount of monomer. The shell thickness also increases with reaction temperature, and in addition, uniformity of the particle size can be improved by raising reaction temperature.