Multimodal particle size distribution

The instrument design is less complicated as compared with laser diffraction. A stable suspension of particles is placed in a transparent cell, where a laser beam impinges on the particles. As the light is scattered from the randomly moving particles, interference patterns are created. Using suitable mathematical algorithms, these patterns are converted into particle size distributions. This technique is not well suited for material that exhibits a multimodal particle size distribution. One should not use this technique to obtain particle size distributions because of the assumptions that are needed to convert the interference patterns into usable information. The technique should be used to assess average particle size only. Additional information on this technique can be found in the literature.2,6,13... 

Small particles and bimodal or multimodal particle size distribution of resin powder yield the highest packing density and consequently the lowest void content, leading to improvement in mechanical properties. 

The critical concentration of powder particles in feedstocks can be increased by using multimodal particle size distributions. If the amount of powder used is split into 25% fines and 75% coarse particles with a diameter ratio of 7 1, respectively, between the two fractions, a higher loading can be obtained without increasing the viscosity [Far 68]. 

For multimodal particle size distributions, the correlation function is the sum of exponentials, each with a decay rate proportional to the average diffusion coefficient of a size mode. To analyse C(r) in this case, a non-linear regres-siaverage particle size. This qiproach is often limited to bimodal distributions due to limitations in signal-to-noise ratio. 

The amounts of water adsorbed onto nanooxides from air correspond to the amounts of water strongly bound (unfrozen at T<213 K) to the surface of nanooxides in aqueous suspensions. In these suspensions, multimodal particle size distributions are observed due to aggregation of primary... 

B. Park, D. Smith, S. Thoma, Determination of agglomerate strength distributions part 4. Analysis of multimodal particle size distributions. Powder Technol. 76(2), 125-133 (1993). doi 10. 1016/50032-5910(05)80019-1... 

Particle size influences the viscosity of a latex, and the industrial demand for high solids latices has led to bimodal and multimodal particle-size distributions (48). Solids levels approaching 70 wt% are possible. The smaller the particle size, the higher the viscosity. 

PMMA is also commonly used In dentistry applications for teeth and dentures. In most cases, several types of particulate filler are used to achieve a multimodal particle size distribution (for a higher particle content) and desired properties like wear resistance, processability, color, and gloss. Under physiological conditions, dental composites take up a certain amount of water. Repeated drying and wetting cycles can result in microcrack formation and accumulation at the interface between the polymer matrix and the inorganic filler (see Figs. 8.32-8.34). 

In the dilute concentration region, where particles hardly ever feel each other, the particle size distribution is not important. For moderate concentrations experimental evidence suggests a minor effect of this parameter. Close to the maximum packing, however, the effect becomes very large (Figure 10.5.3). This can be understood on the basis of the drastic increase in maximum packing when bi-modal or multimodal particle size distributions are used. The effect can be predicted if the maximum packing, calculated or measured. 

If all the resin particles are the same size, the plasticizer must occupy the free volume between the resin particles as well as coat the resin particles in order to permit fiow. If smaller resin particles are able to occupy much of this free volume instead of the plasticizer, more plasticizer is available to coat the resin particles and aid in flow. Through the use of blending resins, one creates a multimodal particle size distribution, which in turn helps to reduce plastisol viscosity. Depending on the particle size distributions of the blending and dispersion resins, there will be an optimum ratio of blending resin to dispersion resin to yield a minimum viscosity. In most resin systems, the ratio of dispersion resin to blending resin fliat yields the minimum viscosity typically ranges between 30 70 and 70 30. ... 

The polyacrylate dispersions optimized in this way for pressure sensitive adhesives are produced and supplied with solids contents between 50 % and 70 %. Average particle sizes are typically between 100 run and 1000 run. However, dispersions with a high solids content (> 60 %) and low viscosity (<500 mPa s) need to have a bimodal or multimodal particle size distributions. The viscosities of most commercial products are generally between 10 and 1000 mPa s but high-viscosity dispersions... 

Schindler, T., Walter, J., Peukert, W., Segets, D., Unruh, T In situ study on the evolution of the multimodal particle size distribution of ZnO quantum dots some general growth rules. J. Phys. Chem. B. 2015b. http //dx.doi.org/10.1021/acs.jpcb.5b08005. In press. 

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