Microcrystalline composites

The polymeric alloys described in section 4.3.1 were principally investigated for use in waveguide applications, and so, to avoid optical losses, concentrations that did not give crystalline precipitates in the polymer were used. Through-plane optics can, however, tolerate poorer optical quality samples, and so microcrystalline polymer samples have been investigated for these applications. 

Samples of m-NA, MNA and KD P in both unorientated and orientated polymer hosts have been prepared [81,82] in concentrations high enough to cause precipitation of microcrystals. PMM, low-density polyethylene 

If acceptable optical losses can be achieved for these systems by controlling the growth and size of the aggregates, the highly efficient molecules being used will make this an attractive approach to practical devices. 

It is possible to produce the LB polymer by polymerizing the monomer on the water surface prior to coating, but this is less attractive than spreading preformed polymers, since unreacted monomer, catalysts and other impurities that may have a detrimental effect on the film can be removed. 

The previous section showed how the design of nlo polymers has evolved from the successful understanding and application of the molecular design of low-molecular-weight crystalline materials. 

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Microstructurc. Crystal size, porosity, and impurity phases play a major role in fixing the fracture characteristics and toughness of an abrasive grain. As an example, rapidly cooled fused aluminum oxide has a microcrystalline stmcture promoting toughness for heavy-duty grinding appHcations, whereas the same composition cooled slowly has a macrocrystalline stmcture more suitable for medium-duty grinding. 

Base-plate wax compositions are generally regarded as trade secrets. A substantial percentage of paraffin is usually present, probably 50—80 wt %. Beeswax [8012-89-3] camauba wax [8015-86-9] ceresin, microcrystalline waxes, Acrawax C (Glyco Products Co. Inc.), mastic gum, rosin [8050-09-7] and synthetic resins may make up the balance of the formulation. Base-plate waxes are generally sold in sheet form about 1.3 mm thick, 75 mm wide, and 140 mm long. 

The compositions of sheet and shape waxes are also trade secrets. However, they are blends of various proportions of paraffin, microcrystalline waxes, camauba wax, ceresin, beeswax, gum dammar, mastic gum, and possibly other resins. Sheet waxes are marketed in square sheets approximately 80 by 90 mm. Various thicknesses are available from 32 gauge (0.5 mm) to 14 gauge (1.63 mm). 

Paper chromatography (PC) and thin layer chromatography (TLC) have been used since the 1940s. Preparative PC on Whatman 3 paper, analytical PC on Whatman 1 paper, and analytical TLC on microcrystalline cellulose, silica gel, or polyamide have been applied with a variety of solvents and the behaviors of anthocyanins have been similar in all media. Two-dimensional TLC allows the separation of several compounds and has been nsed to clarify the anthocyanin compositions of different commodities. ... 

The phase composition of glycine crystal forms during the drying step of a wet granulation process has been studied, and a model developed for the phase conversion reactions [88], X-ray powder diffraction was used for qualitative analysis, and near-infrared spectroscopy for quantitative analysis. It was shown that when glycine was wet granulated with microcrystalline cellulose, the more rapidly the granulation... 

Spherical pellets containing 5% triamcinolone acetonide were prepared by Villar-Lopez and co-workers [59] by extrusion/spheronization following formulation with microcrystalline cellulose and/or a hydrophilic excipient like lactose, sodium earbox-ymethylcellulose, or P-cyclodextrin. Their suitability for coating, with a view toward colonic drug deliveiy, was assessed in terms of their size, sphericity, and dissolution test response. The best results were afforded by a 5 90 5 composition of microcrystalline cellulose, P-cyclodextrin, and triamcinolone acetonide, prepared by complex-ation of triamcinolone acetonide with P-cyclodextrin prior to the addition of microcrystalline cellulose. 

The formation of crystalline fulleride salts at the electrode occurs when less polar solvents and bulky cations are used for the electrosynthesis. The first fulleride salt was synthesized by Wudl by bulk electrolysis of in o-dichlorobenzene with tetraphenylphosphonium chloride as supporting electrolyte [39, 80]. This black microcrystalline material with the composition (Ph4P )3(Cgg )(Cr)2 exhibits an ESR line with a g-value of 1.9991 and a line width of 45 G at room temperature. Single crystals of the slightly different salts (Ph4P )2(Cgg )(Cr) and (Ph4P )2(C50 )(Br ) could be obtained by electrocrystallization and their crystal structure was determined [82, 83]. Magnetic measurements showed the presence of unpaired spins. 

Single-phase microcrystalline semiconductor particles incorporated onto only one side of the BLM represent the most straightforward system. The composition of the electrochemical cell used in investigating System A is explicitly shown in Eq. (29) ... 

Mehra DK, West KP, Wiggins JD. Coprocessed microcrystalline cellulose and calcium carbonate composition and its preparation. US Patent No. 4,744,987, 1988. 

Limwong Y, Sutanthavibul N, Kulvanich P. Spherical composite particles of rice starch and microcrystalline cellulose a new coprocessed excipient for direct compression. AAPS Pharm Sci Tech 2004 5 (article 30). 

J.J. Rocchio J.O. Doall, Analysis of Microcrystalline Waxes Used as Desensitizers in Composition B , BRL Memo Rept 123... 

Aluminium Arsenide, Al3As2.—When a mixture of powdered aluminium and arsenic is heated, no reaction occurs up to 600° C., but above 750° C., if the pressure of the arsenic vapour is kept low, combination takes place with incandescence and results in the formation of a brown microcrystalline powder4 of composition Al3As2. The... 

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