Encapsulated calcium carbonate

Green, D., Walsh, D., Yang, X., Mann, S., Oreffo, R.O.C., 2004. Stimulation of human bone marrow stromal cells using growth factor-encapsulated calcium carbonate porous microspheres. J. Mater. Chem. 14, 2206-2212. 

MCC (65%) and calcium carbonate (35%) Vitacel VE-650 FMC BioPolymer, Newark, Delaware, U.S.A. Direct compression, encapsulation... 

Sukhorukov GB, Volodkin DV, Gunther AM et al (2004) Porous calcium carbonate microparticles as templates for encapsulation of bioactive compounds. J Mater Chem 14 2073-2081... 

Petrov Al, Volodkin DV, Sukhorukov GB (2005) Protein-calcium carbonate co-precipitation. A tool for protein encapsulation. Biotechnol Prog 21 918-925... 

Nature is full of complex constructions designed to encapsulate molecules within a defined space. At one extreme there are cells, enclosed within phospholipid bilayers, and sea dwelling algae like Emiliania huxleyi that are surrounded by calcium carbonate coccoliths which overlap to form an exoskeleton. On a smaller scale are iron storage proteins such as ferritin that are amorphous in the absence of metal ions but form globular structures once metals are bound. 

Ash particles are formed through the thermal decomposition or dehydration of inorganic minerals associated with the coal. Calcium carbonate and clay are the most abundant mineral impurities, with lesser amounts of sulfides, chlorides and oxides also present. The shape of the ash particle is dependent on many factors, two of which are the amount of time and temperature to which the coal is exposed in the combustion chamber (Fisher et al., 1978). The spherical shape, most commonly associated with fly ash particles, shows that complete melting of silicates occurs at high temperature. These spheres may be solid, hollow (cenospheres) or encapsulating spheres (plerospheres). 

Due to their often hydrophilic surfaces, inorganic components have to be hydrophobized in order to incorporate them in hydrophobic polymers. For the encapsulation in polystyrene shells, the surface of calcium carbonate was modified with stearic acid which allowed an encapsulation of about 5 wt% of the inorganic... 

Other inorganic nanoparticles have been encapsulated with miniemulsion polymerization, and a hydrophobilizing agent was used to render the particles hydrophobic prior to minianulsification. For example, calcium carbonate was pretreated with stearic acid prior to being dispersed into the monomer phase. Alumina and magnetite were pretreated with oleic acid, laponite was pretreated with a cetyltrimethylammonium bromide, and silica was pretreated with cetyltrimethyl-ammonium chloride" or methacryloxy(propyl)trimethoxysilane. ... 

Petrov, A. L, Volodkin, D. V, and Sukhorukov, G. B. Protein calcium carbonate co-precip-itation a tool of protein encapsulation. Biotechnol. Prog. 21(3) 918-925 (2005). 

Figure 2.10 Encapsulation of calcium carbonate by the miniemulsion process.

Unsaturated monomers have been adsorbed on to fillers and then polymerised to give encapsulated products. The modulus of the polymer could be modified by selecting the monomer [40]. Acrylic acid-vinyl chloride (1 99) has been polymerised on to calcium carbonate [41] reports of the use of 3,5-triacryloxyhexahydro-S-triazine [42], bis-phenol A and epichlorohydrin [43], methyl methacrylate [44], and acrylic acid [45] have also been published. 

Silanes have little effect on carbon blacks. They are also not generally effective on surfaces such as sulfates and carbonates, although attempts have been made to improve silane effectiveness on such surfaces by pre-coating them with silica [45] or by phosphate layers [46]. It has been reported that some organo-silanes, notably, amino-silanes, can produce an effect on calcium carbonate by some form of encapsulation [47]. 

Recently, Goddart et al. [6] reported a polyvinyl alcohol-copper(ll) initiating system, which can produce branched polymers on surfaces. The initiating system is prepared by dissolving polyvinyl alcohol in water that already contains copper nitrate (or copper chloride). The calcium carbonate filler is dipped into the solution and dried. If this is used for polymerization of an olefin (say, styrene), it would form a polymer that adheres to the particles, ultimately encapsulating them. The mechanical properties of calcium-carbonate-fiUed polystyrene have been found to depend strongly on filler-matrix compatibihty, which is considerably improved by this encapsulation. 

Several fluid bed processes are under development for production and encapsulation of nanoparticles, for example, WC-Co composites, bioceramics (i.e., calcium phosphate hydroxyapapite), carbon encapsulation of iron magnetic nanoparticles, and carbon nanotubes. These nano- or ultrafine powders have broad industrial and pharmaceutical applications. Production processes usually include solution preparation (sol-gel), drying, calcination, and sintering. The last three steps may be realized in a fluidized bed, but fluidization of nano- and ultrafine powders is very difficult because of strong interparticle forces. 

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