Platelet-like

No clinical effects but small depletions in normal white cells count and in platelets likely within 2 days. 

More detailed investigations with planar brushes, obtained from A-B block copolymers, where one component is able to crystallize on the surface of crystalline PE cores of platelet-like aggregates, have been reported recently [175]. 

Figure 1.4 SEM images and EDX data from a Mo9V3W12Ox catalyst after activation during the oxidation of acrolein [35], The pictures indicate that needle-like (A), platelet-like (B), and spherical (not shown) particles are formed during exposure to the reaction mixture. EDX analysis at different spots, two of which are exemplified here, point to V, Mo, and W contents that vary from 19 to 29, 60 to 69, and 11 to 13 atom%, respectively. It was determined that the in situ formation of a (MoVW)5014-type phase accounts for the increase in acrolein conversion observed during the initial reaction stages. (Reproduced with permission from Elsevier.)...

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. 

Since the polymer-filler interaction has direct consequence on the modulus, the derived function is subjected to validation by introducing the function in established models for determination of composite modulus. The IAF is introduced in the Guth-Gold, modified Guth-Gold, Halpin-Tsai and some variants of modified Halpin-Tsai equations to account for the contribution of the platelet-like filler to Young s modulus in PNCs. These equations have been plotted after the introduction of IAF into them. 

Wu et al. [32] introduced the MRF of 0.66 for the platelet-like fillers into established composite models to account for the lower contribution of the plateletlike filler to the Young s modulus than the contribution of the fiber-like filler. This apparently improved the predicting ability of the models in the case of elastomeric nanocomposites. 

Most of the HA crystals in young bone are small with a mean crosssectional width of only about 90 A. Occasionally, larger crystals in the 500 to 1000 A range have a thin platelet-like form. Those two crystal populations are morphologically distinct from one another and must have originated under somewhat different conditions3, 48). 

Table 51 shows an overview of pigments with luster effects. Effect pigments can be classified as metal platelets, oxide-coated metal platelets, oxide-coated mica platelets, platelet-like mono-crystals and comminuted PVD-films (Physical Vapor Deposition). Aims of new developments are new effects, colors, improvement of hiding power, increase of the interference color, increase of light and weather stability and improved dispersibility characteristics. Of special interest are pigments which are toxicologically safe and which can be produced by ecologically acceptable processes. 

New Developments Based on Non-Micaceous Systems. The class of single crystal lustrous pigments is not limited to the non-absorbing types like bismuth oxychloride and basic lead carbonate. Recent developments are absorbing pigments such as platelet-like graphite, laminar phthalocyanines and flaky iron oxides. These flakes... 

Several developments are concentrated on the search for substrate containing systems, where mica is replaced by other platelet-like materials. So it is possible to replace mica by kaoline or talc to produce bright conductive pigments by coating with (Sn,Sb)02 [5.243],... 

Random copolymers of VF2/F3E when crystallized from the molten state above the Curie temperature show a microstructure in the form of very thin needle-like morphological units which are probably semicrystalline. Figure 5a illustrates the needle-like microstructure of the copolymer 80/20 melt crystallized in the paraelectric phase observed at 140 °C. After codling at room temperature the microstructure of the ferroelectric crystals is such that what appear in the optical microscope as radial fibers are, in fact, stacks of thin platelet-like morphological units (see Fig. 5b). 

Fig. 5. a. Needle-like microstructure of the 80/20 copolymer. Sample cast from dimethyl formamide molten at 180 °C and recrystallized at 140 °C in the paraelectric phase, b. Stacks of thin platelet-like crystals of the same copolymer after cooling the sample at room temperature in the ferroelectric phase. Scale bars, 25 pm... 

Although the lipid phase in powdered toppings is finely dispersed in the form of small globules (< 1 /am), strong destabilization takes place after reconstitution in cold water, resulting in platelet-like crystal agglomerates (Figures 6 and 7). 

Practically applied platelet-like crystalline materials are produced with layer thickness (d) which are necessary to obtain the desired interference colors (iridescence) [11], Most of the pearlescent pigments synthesized today consist of at least three layers of two materials with different refractive indices. A simplified structure of such pigments and their interaction with light is shown in Fig. 15.4. For the case of metal oxide-mica pigments, thin flakes of mica (thickness ca. 500 nm, compara-... 

The barrier effect can be achieved, for example, by using pigments with a platelet-like or lamellar particle shape. This allows them to form a wall of flat particles within a paint film and therefore water and electrolytes have to take an extended/less direct route through the paint film to the substrate. 

Prevention of the coalescence of the sticky, partially polymerized particles is a major problem in suspension polymerizations, and proper selection of stabilizing agents is important. Two kinds of additives are used to hinder coalescence of particles in suspension polymerizations. These are platelet-like mineral particles that concentrate at the organic-water interface, like Ca3(P04)2, and/or macromolecu-lar species that are soluble in water and insoluble in the particular organic phase. Poly(vinyl alcohol) and starch products are examples of the latter type. 

When the shapes of crystallites are isotropic, random distribution of their orientations is not a problem and deviations from an ideal sample are usually negligible. However, quite often the shapes are anisotropic, e.g. platelet-like or needle-like and this results in the introduction of distinctly non-random crystallite orientations due to natural preferences in packing of the anisotropic particles. The non-random particle orientation is called preferred orientation and it may cause considerable distortions of the scattered intensity. 

Consider two limiting anisotropie particle shapes platelet-like and needle-like. The platelets, when packed in a flat sample holder, will tend to align parallel to one another and to the sample surface. Then, the amount of plates that are parallel or nearly parallel to the surface will be much greater than the amount of platelets that are perpendicular or nearly perpendicular to the surface. In this case, a specific direction that is perpendicular to the flat... 

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