Particle structure

In addition to homopolymers of varying molecular and particle structure, copolymers are also available commercially in which vinyl chloride is the principal monomer. Comonomers used eommercially include vinyl acetate, vinylidene chloride, propylene, acrylonitrile, vinyl isobutyl ether, and maleic, fumaric and acrylic esters. Of these the first three only are of importance to the plastics industry. The main function of introducing comonomer is to reduce the regularity of the polymer structure and thus lower the interchain forces. The polymers may therefore be proeessed at much lower temperatures and are useful in the manufacture of gramophone records and flooring compositions. 

Once it is recognized that particles adhere to a substrate so strongly that cohesive fracture often results upon application of a detachment force and that the contact region is better describable as an interphase [ 18J rather than a sharp demarcation or interface, the concept of treating a particle as an entity that is totally distinct from the substrate vanishes. Rather, one begins to see the substrate-particle structure somewhat as a composite material. To paraphrase this concept, one could, in many instances, treat surface roughness (a.k.a. asperities) as particles appended to the surface of a substrate. These asperities control the adhesion between two macroscopic bodies. 

All large lumps or particles contain cracks, microcracks or lines of weakness. Any normal particle structure will contain imperfections, dislocations and... 

Friedrich KA, Henglein F, Slimming U, Unkauf W. 1998. Investigation of Pt particles on gold substrates by IR spectroscopy—Particle structure and catalytic activity. Colloids Surf A 134 193-206. 

Particle Structure. First of all, the particle structure has a fundamental influence on the degradation propensity. The extent of degradation as well as its mode will strongly depend on whether the particle is a single crystal, has an amorphous structure or is an agglomerate. For example, spray-dried catalysts, which are often used in fluidized bed reactors, are... 

In the elastic floe model, the structural units (which persist at high shear rates) are assumed to be small floes of particles (called floccules) which are characterized by the extent to which the particle structure is able to trap some of the dispersion medium. The degree to which liquid is trapped in the floe is measured by the floe volume ratio, CFF, given by,... 

Pilot sewer studies are often carried out in systems operating with recirculation. Specific care must be taken in systems where water-gas exchange processes form a part of the mass balance. Critical points are pumps and bends that may change the flow regime, air-water exchange processes, biofilm and particle structure. Figure 7.2 is a sketch of a pilot sewer used for sewer process studies (Tanaka and Hvitved-Jacobsen, 2000). 

The new TEM techniques can provide a full characterization of small particles. The combination of weak beam images and microdiffraction information can render a very complete picture of the particle structure. In addition, refracted electron images can be... 

Figure 6. Different particle structures in high impact polystyrene (73) (85).

Temperature fluctuations give rise to changes in particle structure and to greater cohesiveness. 

To exceed the typical filler reinforcement and to obtain a real nanocomposite, it is necessary to destroy the primary particle structure during processing ... 

The charcoal, or rather the coated charcoal, contributes to the fountain effect as does the gunpowder and aluminium by processes such as those described above. The flitter aluminium has a rather coarser particle structure than does the fine aluminium so that sparks from the former are longer lived and can survive a greater drop-height. Antimony trisulfide is commonly used to enhance the glittering effect in a series of chemical reactions with the gunpowder and aluminium. 

Flagan RC, Lunden MM (2004) Particle structure control in nanoparticle synthesis from the vapor phase. 204 113-124... 

Metal catalysts composed of more than two different metal elements are of interest from both technological and scientific viewpoints for improving the catalyst quality or properties (20). In fact, bimetallic (or multimetallic) catalysts have long been valuable for in-depth investigations of the relationship between catalytic activity and catalyst particle structure (21). Sinfelt et al. have made a series of studies on bimetallic nanoparticle catalysts supported on inorganic supports, for example,... 

Hart, R. W., and E. P. Gray, 1964. Determination of particle structure from light scattering, J. Appl. Phys., 35, 1408-1415. 

Further factors influencing rheological characterization of filled polymers include changes in the degree of filler dispersion or inter-particle structure forma-... 

It has thus been shown that the present theory of charged particle equilibria necessarily leads to point-like configurations with an excessively small characteristic radius r0, permitted, in principle, even to approach the limit r0 = 0. In this way the integrated field quantities can be rendered finite and nonzero. As pointed out in Section V.A.l.b, a strictly vanishing radius would not become physically acceptable, whereas a nonzero but very small radius is reconcilable both with experiments and with the present analysis. It would leave space for some form of internal particle structure. A small but lower limit of the radius would also be supported by considerations based on general relativity [15,20]. 

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