Crystal Crystallinity

It is pertinent to mention here that in the course of TGA many vital processes, for instance crystallization, crystalline transitions, pure fusion reactions, glass transitions, and solid-state reactions devoid of volatile components might not be indicated as they happen to cause little change in weight of the sample. TGA invariably describes with ample precision the stoichiometry related to chemical changes that are indicated during DTA by an endothermal or exothermal duration from the base-line. 

One of the primary limitations of PET is related to its slow rate of crystallization from the melt. A consequence of this is that relatively long cycle times are required to provide crystallinity in PET. When this is achieved, it is often accompanied by opacity and brittleness, due to the relatively large size of crystallites formed by thermal crystallization. Crystallinity itself is often desirable in moulded parts, due to the higher thermal and mechanical stability associated with it. Crystallinity is especially desirable when parts are intended to be subjected to elevated temperatures since if the PET components are amorphous they will anneal at temperatures above 80 °C. 

White crystals, crystalline solid, or light pink liquid which slowly turns brown on exposure to air. Phenol has an acrid or sweet, tarry-like odor resembling wet newspaper or cardboard. Sharp burning taste. At 40 °C, the average odor threshold concentration and the lowest concentration at which an odor was detected were 31 and 9.5 pg/L, respectively. At 25 °C, the lowest concentration at which a taste was detected was <2 pg/L (Young et al., 1996). Leonardos et al. (1969) and Nagata and Takeuchi (1990) reported odor threshold concentrations of 47 ppmv and 5.6 ppbv, respectively. 

Copper Sulfate occurs as blue crystals, crystalline granules, or powder. It effloresces slowly in dry air and is freely soluble in water, soluble in glycerin, and slightly soluble in alcohol. 

Potassium Metabisulfite occurs as white or colorless, free-flowing crystals, crystalline powder, or granules. It gradually... 

Potassium Sorbate occurs as white to off white crystals, crystalline powder, or pellets. It decomposes at about 270°. 

In the second step (Figure 10-4) we add just enough IPA to cause the polymers to become acid-capped. We use IPA and not TPA IPA makes the chain less regular, so that it will not crystallize (crystalline polymers are difficult to process). The melt is then cooled and milled to a powder. 

Colourless transparent or white crystals, crystalline masses, blocks, or powdery masses known as flowers of camphor . M.p. 174° to 181°. 

White or yellowish-white acicular crystals, crystalline plates or crystalline powder. It acquires a brownish-pink tint on exposure to light and air. M.p. 62° to 68°. 

Colourless crystals, crystalline flakes, or white or faintly pink powder. Soluble 1 in 1 of water and 1 in 11 of ethanol practically insoluble in chloroform and ether. Concentrated aqueous solutions are liable to deposit crystals of the hexahydrate on standing. 

The microfibrils should be almost completely crystalline as can be concluded from the following consideration. The measured value u)c(DSC) of 75% refers to the total amount of PET in the blend. The amorphous part (25%) of the PET is involved in copolymers with PA6 as indicated above, but this is not the case with the crystalline PET (microfibrils). For this reason and because of the outlined structure formation peculiarities the microfibrils should be of very high crystallinity. This explanation is also supported by another observation. As mentioned above, the H of PET crystallized under pressure is 400 MPa (Balta Calleja et al., 1994). Detailed structural analysis of such samples shows that they are almost completely crystalline (Wc = 90%) and consist of rather large crystals (crystalline lamellae around 10-15 nm). Only by having this similarity in the structural characteristics does one obtain extremely high H values (Baltd Calleja, etal., 1994). 

Physical state Heavy, mobile, liquid metal Solid mercury is ductile, maleable mass which may be cut with a knife Crystals, granules or powder rhombic crystals, crystalline solid0 Heavy amorphous powder, also occurs as black cubic crystals (mercuric sulfide, black) powder, lumps, hexagonal crystals (mercuric sulfide, red) Heavy powder rhombic crystals or crystalline powder 1... 

Needham, D. and Evans, E. (1988) Struemre and mechanical properties of giant lipid (DMPC) vesicle bilayers from 20-degrees-C below to 10-degrees-C above the liquid-crystal crystalline phase transition at 24-degrees-C. Biochemistty, 27 (21), 8261-8269. 

Physical state Powder or crystal Crystal Crystalline powder Crystalsb... 

This chapter surveys unimolecular and bimolecular photochemical reactions in mixed molecular crystals and solid mixtures. Various photoreactions occurring in mixed crystals (solid solution), hydrogen-bonded cocrystals, donor-acceptor crystals, crystalline organic salts, and solid mixtures are described. In contrast to one-component crystals [2], the organic photochemistry of such multi-... 

The polymerization system and the processes taking place in it can be presented as follows The growing macromolecule can be either fully crystallized so that the active center is located on the surface of the crystal (crystalline polymer) or it can be partially dissolved in the medium, with the active center located at the dissolved end of the chain section (dissolved polymer). The equilibrium monomer concentrations of the polymer differ in the dissolved and the crystalline state. Addition to the surface active center with the formation of a solid polymer is thermodynamically more favourable than addition to the active center in solution with the formation of a dissolved polymer. 

Solar cells can be made from single crystals, crystalline and amorphous semiconductors. For simplicity this article begins with a description of crystalline material. 

Zinc Insulin Crystals. Crystalline preparation of the active antidiabetic principle of the internal secretion of Langerhans islands of the pancreas. The crystals contain a small amount of zinc (not less than 0.45% nor more than 0.9%), which is chemically combined with the active principle. Each milligram nf the crystals is equivalent to not less than 22 units of insulin. The product is marketed in the form of cryst zinc-insulin injection. Study of the binding of zinc by insulin Tanford, Epstein, J. Am. Chem. Soc. 76, 2170 (1954) Cunningham, et al ibid. 77, 5703 (1955). Proposed crystallographic structure Marcker, Graae, Acm Chem. Sea rid. 16, 41 (1962). 

PI Di-n-octadecyl ester of itaconic cryst. crystallization, crystalline,... 

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