Particle size distribution spacer particles

Kenyon CJ, Dewsbury NJ, Newman SP. Differences in aerodynamic particle size distributions of innovator and generic beclomethasone dipropionate aerosols used with and without a large-volume spacer. Thorax 1995 50 846-850. 

Figure 8-5. Typical particle size distribution curves of HIPRESICA N3N series and DVB spacers. The average diameter of both spacers is the same at6 fim. The C. V. values of HIPRESICA and DVB spacers are 1.59% and 4.79%, respectively.

Silica spheric particles for spacer are employed to keep the thickness of the liquid crystal layer, that is, the gap between two glass panels constant (Toda, 1996 Adachi, 1998). Silica spheric particles of 5-10 / m with very sharp size distribution are used. In order to fabricate the big spheric particles for spacers, fine particles are produced by Stober technique, and then the particles are grown by adding silicon tetraethoxysilane to the solution. 

An example of photographs of silica spacer particles dispersed in the sealant is shown in Figure 8-4, in order to obtain a general idea on the particle-size distribution and dispersion in sealant. 

Additional applications of DOTM include observing deposition and critical fluxes for yeast, algae and bacterial cells [10, 15-17], and particle deposition patterns that occur when spacers are used in the membrane channels [18]. Spacers were shown to increase the critical flux by up to two times [19]. Observations of the deposition and removal of submicron bacteria required the use of fluorescence. Removal of the bacterial cake when the flux was reduced below the critical value was observed to occur in floes [16]. In a recent application of DOTM, Zhang, Fane and Law [20] showed that the presence of larger particles increased the critical flux of smaller particles in a mixture and that only the smaller particles selectively deposited from a mixture when the imposed permeate flux was above this critical flux. This finding is consistent with the earlier observation of Li et al. ]10] that the smaller particles are preferentially deposited from a feed distribution of particle sizes. 

Applications of microparticles can be found in medicine, biochemistry, colloid chemistry, and aerosol research [48]. Some uses include separation media for chromatographic application, high surface area substrates for immobilized enzymes, standards for calibration, spacers in optical cavities and liquid crystal displays, and three-dimensional microenvironments for cell encapsulation. It should be stressed that even a scaled-up MF synthesis enables generation of a relatively small amount of particles, in comparison with conventional emulsion, dispersions, or suspension polymerizations. Thus, most practical applications of such microbeads should utilize their high-value unique properties, for example, a uniform distribution of sizes and control of morphology, structure, and shape. Therefore, some of the demonstrated applications of polymer microbeads are still in the proof-of-concept stage. 

---