Encapsulation of inorganic particles

The microencapsulation of pigment and filler particles is an important area of research, both in academic research world and in industrial laboratories. Many activities in the past decade have been aimed at obtaining inorganic powders, coated with an organic polymer layer. Such systems are expected to exhibit properties other than the sum of the properties of the individual components. In general, several benefits from this encapsulation step can be expected when the particles are incorporated in a polymeric matrix (e.g. plastics or emulsion paints)  

The applications of these encapsulated particles relate to the above-mentioned benefits and can be found in filled plastics, paints, inks, paper coatings etc. (van Herk German, 1999). 

When the inorganic particles are magnetically responsive this opens pathways to special applications, such as coupling of enzymes and antibodies to the surface of the magnetic particles after which drug targeting becomes possible (see Chapter 10). These particles can also be used in biochemical separations (Arshady, 1993). 

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Fig. 12.1.5 Polymer encapsulation of inorganic particles by polymerization of adsorbed surface active monomer.

Erdem, B., E. D. Sudol, V. L. Dimonie, and M. S. El-Aasser, Encapsulation of inorganic particles via miniemulsion polymerization. I. Dispersion of titanium dioxide particles in organic media using OLOA 370 as stabilizer. J. Polym. Sci. A Polym. Chem. 38 (2000) 4419-4430. 

Although some papers on encapsulation of inorganic particles can be found before 1980, most of the early work begins in the mid-1980s and, on average, about 50 papers per year were published on the topic of encapsulation using the emulsion polymerization technique. 

Encapsulation of Inorganic Particles with Emulsion Polymerization... 

Erdem B, Sudol ED, Dimonie VL et al (2000) Encapsulation of inorganic particles via miniemulsion polymerization. III. Characterization of encapsulation. J Polym Sci Part A Polym Chem 38 4441-4450... 

Emulsion polymerization is the polymerization technique that starts with emulsified monomer in the continuous aqueous phase. Polymer formation takes place in the micelles and is initiated by water-soluble initiators. The monomers are insoluble or sparingly soluble in water. Emulsion polymerization is used very frequently in order to perform encapsulation of inorganic particles with polymers where water-based coatings are required. For the encapsulation of inorganic particles, seeded emulsion polymerization is performed hydrophobic inorganic particles are dispersed with normal surfactants or protective colloids in the aqueous phase. As polymerization on the surface of inorganic particles is always in competition with secondary particle formation, the concentration of the surfactants should be lower than their critical micelle concentration. However, homogeneous nucleation can also occur, which... 

No.24, 15th Dec.2000, p.4441-50 ENCAPSULATION OF INORGANIC PARTICLES VIA MINIEMULSION POLYMERIZATION. III. CHARACTERIZATION OF ENCAPSULATION... 

Engineering. Volume SO.Conference proceedings. Anaheim, Ca., Spring 1999, p.583-4 ENCAPSULATION OF INORGANIC PARTICLES VIA MINIEMULSION POLYMERIZATION Erdem B Sudol E D Dimonie V L El-Aasser M S Lehigh University... 

Polytner Encapsulation of Inorganic Particles 99 Table 4.3 Some commercial silane and organotitanate coupling agents. 

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