Microbeads manufacture

Beaded polymeric supports are produced by a two-phase suspension polymerization in which microdrops of a monomer solution are directly converted to the corresponding microbeads. The size of a microdroplet is usually determined by a number of interrelated manufacturing parameters, which include the reactor design, the rate of stirring, the ratio of the monomer phase to water, the viscosity of both phases, and the type and concentration of the droplet stabilizer. 

Given the complex process to produce mesophase carbon (graphitized microbeads and fibers), natural graphite can be very competitive in terms of its manufacturing costs [18]. The physical characteristics of certain SLC type materials are extremely close to the characteristics of state-of-the-art MCMB grades. 

Attempts were made to discover the correlation between the crystalline structure of carbonaceous materials and their capability to reversibly intercalate lithium. This correlation has not been definitely established, but still, one can assume as a certain general principle that the optimum materials would contain an amorphous matrix with inclusions of a mesophase nuclei of graphite crystallites. Such materials are various cokes, pyrographite, and products of pyrolysis (carbonization) of various polymers. For practical purposes, the industry mastered some special materials providing high characteristics of negative electrodes in lithium ion batteries. The most popular material is manufactured by the Japanese company of Osaka Gas Co. under the name of mesocarbon microbeads, MCMB it represents the carbonization product of pitchy resins under a certain temperature regime. 

Some skin care preparations use polyethylene microbeads that serve as exfoli-ants. The particles in municipal waste reach the oceans via wastewater and are potent marine pollutants as well as a pathway that introduce concentrated persistent chemicals (POPs) in seawater to the marine food web (microparticles see Chapter 9). On recognizing the environmental damage posed by these, several leading manufacturers have pledged to phase out their use of these and to undertake research to identify nonpolluting replacement,... 

In response to such campaigns, several multinational manufacturers of products containing plastic microbeads committed to phasing out their use. The timing of these commitments reflected the practical business reality that it takes time to reformulate products. Some companies committed to phasing out the use of microbeads within a year, others within a three-year period [168,169]. 

Based on "retail regulation" and emerging regulatory actions by various governmental bodies, many manufacturers have committed to phasing microbeads out of their products. One might conclude that this demonstrates... 

Membrane and microfiuidic devices have also been adopted for the precision manufacture of solids from double-emulsion templates. To date, several different types of particles have been successfully produced by incorporating use of various membrane and microfiuidic devices in processes of polymerization, gel formation, crystallization, and molecular or particle self-assembly. Membrane emulsification is more suited to the fabrication of less sophisticated particulates, such as solid lipid micro-Znanoparticles, gel microbeads, coherent polymeric microspheres, and inorganic particles such as silica microparticles. Microfiuidic devices allow more sophisticated particle designs to be created, such as colloidosomes, polymerosomes, 3D colloidal assemblies, asymmetric vesicles, core-shell polymer particles, and bichromal particles. 

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