Particles characteristics related

Plasticization, whether internal (by copolymerization) or external (with additives), is also extremely important for proper performance at the time of apphcation. The ease of coalescence and the wetting characteristics of the polymer emulsion particles are related to their softness and the chemical nature of the plasticizer. 

Table 6.2 summarizes the low pressure intercept of observed shock-velocity versus particle-velocity relations for a number of powder samples as a function of initial relative density. The characteristic response of an unusually low wavespeed is universally observed, and is in agreement with considerations of Herrmann s P-a model [69H02] for compression of porous solids. Fits to data of porous iron are shown in Fig. 6.4. The first order features of wave-speed are controlled by density, not material. This material-independent, density-dependent behavior is an extremely important feature of highly porous materials. 

Fig. 1.2.12 Relation between concentration and particle characteristics. (From T. Ogihara et al., J Soc Powder Technol Jpn 31, 620 (1994). Courtesy of H. Masuda, The Society of Powder Technology, Kyoto, Japan.)...

Theoretically, no equation can completely describe the physical properties of a packing without taking into account particle-diameter, size-distribution, and other particulate parameters already mentioned. The reason for their omission in some equations is threefold (a) The equation may contain arbitrary constants related to particle-characteristics constituting the packing (b) the derivation of the equation may be in terms of an ideal or isotropic medium, and (c) the equations may be empirical. So far, statistical analysis seems to have played only a small role in studies of packing problems, and probably will continue to do so until the particulate properties of various materials are better understood and made subject to mathematical treatment. 

Most of the early experimental investigations were performance studies concerned with the homogeneity of solid-liquid suspensions or with the rate of solution of solid particles as related to various operating characteristics. This class of systems has not been studied to any extent from a fundamental standpoint the following sections will indicate the large regions of interest which remain to be investigated. 

Several crystallization objectives have been recommended to favor downstream operations or product quality. One can maximize the number-mean or weight-mean crystal size, maximize the final size of crystals grown from seed crystals, or minimize the ratio of nucleated crystal mass to seed crystal mass.f ° Other particle size-related characteristics of product crystals that have been optimized during crystallization include the coefficient of variation and the crystal shape. Although the weight-mean crystal size is the most commonly used objective in optimal control studies, the weight-mean crystal size is too insensitive to the number of small crystals that can cause filtration problems when used as an objective to optimize the crystallization operations. 

Characteristics relating to the resistance to destruction such as the particle strength, the probability of breakage, the mass-related work input or the specific reaction force. 

Choice depends on particle characteristics (size, flowability, corrosiveness, abrasiveness, handhng characteristics, safety-hazard [static electrification, fumes, flammability]), and vertical versus horizontal distance. A related topic is covered in Section 16.11.2.5, and bins for storage (Section 16.11.6.35). 

Order of magnitude of dimensionless (related to the radius of drops or solid particles) characteristic sizes of regions of diffusion wake in translational Stokes flow at high Peclet number... 

The second characteristic relates to the extreme minuteness of the colloidal particles. It is known that at the surface of all bodies is found a layer of molecules which, by reason of their asymmetric porition, are submitted to different forces from those which act on the molecules situated in the interior. Here the superficial layer assumes a r61e of great importance to the whole molecular structure. It has been established that the thickness of the first is of the same order of size as the diameter of the second, from 20 to 50 millionths of a millimeter. In addition, around the colloidal particle is found an adsorption layer, formed by adherent liquid, which forms a sort of envelope isolating the colloidal substance from the rest of the surrounding medium. The composition of the adsorption layer is not always the same as that of the mass of the liquid. There may be in this region a concentration of the dissolved parts, or, on the other hand, a dilution, so that the material considered, protected by this double envelope — superficial layer and adsorption layer — no longer reacts as it would have done had it preserved its normal condition. 

The objective of this section is to elucidate some of the current literature findings of environmental and health/safety issues with airborne nanoparticles. The Uterature review of the most recent articles in this area includes topics related to the multiple components of the risk assessment framework. This includes such important aspects as particle characteristics effecting toxicity, their fate and transport throughout the environment, the routes of exposure and the metrics by which exposure ought to be measured and the mechanisms of translocation to different parts of the body. In addition, recent studies are presented that involve the characterization of nanoparticles in the workplace during different operations and conditions. 

PTFE particles as the antifoam material. A correlation between the foam volume destroyed and the receding contact angle was found from this study (Figure 8.7). The antifoam action for these spherical particles was related to the wettability, contact angle and the bridging characteristics for this particular system. 

---