Particles ribbon-like

Acryhc and modacryhc fibers are sold mainly as staple and tow products with small amounts of continuous filament fiber sold in Europe and Japan. Staple lengths may vary from 25 to 150 mm, depending on the end use. Eiber deniers may vary from 1.3 to 17 dtex (1.2 to 15 den) 3.2 dtex (3.0 den) is the standard form. The appearance of acryhcs under microscopical examination may differ from that of modacryhcs in two respects. Eirst, the cross sections (Eig. 1) of acryhcs are generally round, bean-shaped, or dogbone-shaped. The modacryhcs, on the other hand, vary from irregularly round to ribbon-like. The modacryhcs may also contain pigment-like particles of antimony oxide to enhance their flame-retardant properties. 

A—Pyrolytic carbon showing ribbon-like structure in vitrinoid bands. B—Faint gray lines define compression cracks in a bright micrinoid particle. C—Pyrrhotite (white) formed by the thermal decomposition of pyrite impregnating semifusinoids (gray). D—Bright coke particles in a baked-bone coal layer... 

The SDBS-adsorbed material did not show nanoribbons, even at high surfactant concentrations. Nanoribbons were observed for both the SOS- and SOBS-adsorbed materials, as can be seen in Figures 5 and 6. However, their incidence in the SOS-adsorbed material reached only 5% of the particles analysed, while in the SOBS-adsorbed LDH this ribbon-like images were observed in about 90% of the particles. 

The sedimentation FFF process is illustrated in Figure 1. In this figure, the FFF channel, which has a ribbon-like rather than a tube-like configuration, is curved to fit within a centrifuge basket. The centrifuge is responsible for the sedimentation forces which impel particles toward the accumulation wall. Naturally, the largest and most massive particles are impelled by the greatest forces and end up closest to the wall, provided their density differs from that of the channel fluid. 

EPDM particles) are clearly visible on the fracture surface. The ribbon-like structures visible on the fractured surfaces are probably the micro-shear bands in the blends. 

The thickness of the lamellae depends on the crystallization temperature and is usually in the order of 6-10 nm. The macromolecules are normal to the lamellae and are folded back and forth on themselves. A single-polymer molecule may belong to more than one lamella, especially in polymers crystallized from the melt. Such interlamellar bonding increases as the molecular weight increases. Chain-folding also exists in some of the fibrous or ribbon-like structures in which nylons may crystallize. These structures are presumed to be the degenerated forms of lamellae. The structure of the observed globular particles appears to be unknown. 

Smectic substances are crystalline-liquid substances in which elongated filament or ribbon-like molecules are arranged in such positions that both ends lie preferably in given planes. Fig. 71 will show a diagrammatic representation of this type of arrangement. Apart, however, from this grouping of the individual particles, they are free to move to a large extent they can rotate around their axes, and be displaced in such a way that the axes remain parallel and the number of the chains comprised in a bundle, as shown in Fig. 71, can vary molecules from one set can pass over to another, etc. 

Figure 12-30. Structures of cellulose microfibrils synthesized by distinct TCs. Note cross sectional views of cellulose microfibrils (oblique lines) and particle arrangement of TCs on the fractured face of the plasma membrane. (A) A bundle consisting of 2-nm fine fibrils, which is synthesized by a dinoflagellate TC (a). (B) A thin, ribbon-like microfibril synthesized by each of phaeophycean and eustigmatophycean TCs (b), and rhodophycean (c), xanthophycean (d), and phaeothamniophycean TCs (e). (C) A large microfibril synthesized by each of ulvophycean (f), chlorophycean (g), and glau-cophycean TCs (h). (D) A 3.5-nm microfibril synthesized by a rosette TC (i). (E) A microfibril with a parallelogrammic section synthesized by a tunicate TC (j).

Figure 12-25. Plots of viscosity vs. shear-ratefor alumina sols. Arrows show the direction of the changeofshearrate.Thepoints ( ) and cross-marks (x) denote the values obtainedwhen the shear rate is increased and decreased, respectively. Sol A contains granular particles and Sol B contains ribbon-like particles. From Maki (1988), withpermission of Elsevier.

In this model, the filler particles are disk shaped, whereas in the previous two models the particles are assumed to be ribbon-like. These plate-like particles are impermeable with net orientation of the plates, but there is no positional order for the plates, which creates a nematic phase. This model focuses on dilute and semidilute regimes (i.e., the volume fraction of particles is small). It is assumed that the permeability of the polymer is not infiuenced by the presence of particles in the matrix. The final equation given by Fredrickson and Bicerano is Eq. (8.5),... 

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