Unions, dispersion

Ibrahim, N.A., El-Zairy, E.M.R., 2009. Union disperse printing and UV-protecting of wool/ polyester blend using a reactive b-cyclodextrin. Carbohydr. Polym. 76,244-249. 

Phloroglucinol is Hsted in the Colourindex as Cl Developer 19. It is particularly valuable in the dyeing of acetate fiber but also has been used as a coupler for azoic colors in viscose, Odon, cotton (qv), rayon, or nylon fibers, or in union fabrics containing these fibers (157). For example, cellulose acetate fabric is treated with an aromatic amine such as (9-dianisidine or a disperse dye such as A-hydroxyphenylazo-2-naphthylamine and the amine diazotizes on the fiber the fabric is then rinsed, freed of excess nitrite, and the azo color is developed in a phloroglucinol bath at pH 5—7. Depending on the diazo precursor used, intense blue to jet-black shades can be obtained with excellent light-, bleach-, and mbfastness. 

In the manufacture of highly resident flexible foams and thermoset RIM elastomers, graft or polymer polyols are used. Graft polyols are dispersions of free-radical-polymerized mixtures of acrylonitrile and styrene partially grafted to a polyol. Polymer polyols are available from BASF, Dow, and Union Carbide. In situ polyaddition reaction of isocyanates with amines in a polyol substrate produces PHD (polyhamstoff dispersion) polyols, which are marketed by Bayer (21). In addition, blending of polyether polyols with diethanolamine, followed by reaction with TDI, also affords a urethane/urea dispersion. The polymer or PHD-type polyols increase the load bearing properties and stiffness of flexible foams. Interreactive dispersion polyols are also used in RIM appHcations where elastomers of high modulus, low thermal coefficient of expansion, and improved paintabiUty are needed. 

Unions can also be a serious source of dispersion, depending on their design. Today, low dead volume unions are generally available which exhibit reduced dispersion... 

It is seen that the normal union can cause significant dispersion and, by drilling out the union, the dispersion is greatly reduced. It must be assumed that the dispersion caused by the modern reduced volume union would fall somewhere between these two extremes. The same authors also measured the dispersion arising from stainless steel frits and their results are shown in Table 4. 

Extra-column dispersion can arise in the sample valve, unions, frits, connecting tubing, and the sensor cell of the detector. The maximum sample volume, i.e., that volume that contributes less than 10% to the column variance, is determined by the type of column, dimensions of the column and the chromatographic characteristics of the solute. In practice, the majority of the permitted extra-column dispersion should... 

When the CMC determination is made by surface tension measurements, the resulting curve appears without minimum as a single surfactant. It is probable that an inversion takes place through the adsorption of the LSDA onto the surface of the Ca soap micelle, so that complete precipitation does not occur [23]. Zhang and Xiao [32] are of the opinion that the dispersion comes from the union of LSDA with the free ionic soap molecules. The particles from the soap-LSDA mixture are far larger than the corresponding soap molecules in soft water and therefore result in turbidity in hard water. 

As the solvent mixture also contained 225 mg of tetramethyl ammonium hydroxide pentahydrate per liter at a high water content (75%), the surface of the reverse phase would have been largely covered with the tetramethyl ammonium hydroxide pentahydrate. This would have acted as an adsorbed ion exchange stationary phase. It is clear that the free acids, salicylic acid, acetylsalicylic acid (aspirin) and benzoic acid were retained largely by ionic interactions with adsorbed basic ion exchanger and partly by dispersive interactions with the exposed reversed phase. The acetaminophen and the caffeine, on the other hand, being unionized substances, were retained only by dispersive interactions with the exposed reversed phase. 

Military weapons tests conducted at the Pacific Proving Grounds in the 1940s and 1950s resulted in greatly elevated local concentrations of radionuclides, and an accident at the Chernobyl nuclear power plant in the former Soviet Union in 1986 resulted in comparatively low concentrations of radionuclides dispersed over a wide geographical area. Both cases are briefly reviewed. 

The effect of environmental concerns on future developments in the paint industry is discussed. Particular attention is paid to volatile organic compound regulations, developments in powder coatings, and radiation-curable coatings. Tabulated information is presented on applications, backbone type and typical mechanical properties of Incorez W830 series PU dispersions and Incorez W2000 series uiethane/aciylic hybrids. 10 refs. EUROPEAN COMMUNITY EUROPEAN UNION UK WESTERN EUROPE... 

It is highly improbable that a nuclear fission power plant would ever explode like a nuclear bomb, but a loss of coolant accident could result in a melt down condition. In a melt down, a large amount of radiation can be released at ground-level. A nuclear or conventional chemical or steam explosion could disperse much of the radioactive particles into the atmosphere. This is essentially what happened when the Chernobyl gas explosion occurred in the Soviet Union in 1986. 

Table 5.2 Summary of selected analytical methods for molecular environmental geochemistry. AAS Atomic absorption spectroscopy AFM Atomic force microscopy (also known as SFM) CT Computerized tomography EDS Energy dispersive spectrometry. EELS Electron energy loss spectroscopy EM Electron microscopy EPR Electron paramagnetic resonance (also known as ESR) ESR Electron spin resonance (also known as EPR) EXAFS Extended X-ray absorption fine structure FUR Fourier transform infrared FIR-TEM Fligh-resolution transmission electron microscopy ICP-AES Inductively-coupled plasma atomic emission spectrometry ICP-MS Inductively-coupled plasma mass spectrometry. Reproduced by permission of American Geophysical Union. O Day PA (1999) Molecular environmental geochemistry. Rev Geophysics 37 249-274. Copyright 1999 American Geophysical Union...

One recent development in Ziegler Natta catalysts was in producing catalyst particles that expanded as the polymerization reaction occurred. In this polymer the catalyst remains dispersed throughout the polymer, retaining its activity. This led to the development of fluidized bed processes to make polyethylene and polypropylene in which a sphere of polymer formed around each initial catalyst particle, and the polymer remained sohd as the reaction proceeded, rather than requiring a liquid solution. A major class of these catalysts and fluidized bed reactor was developed by Union Carbide and by Shell Oil and called the Unipol process. In this process a very active solid catalyst is introduced into the reactor, and reaction occurs on the catalyst particles, which expand to maintain active sites on the growing polymer sphere. 

These two characteristic qualities of the gels are best interpreted on the assumption that the disperse phase does not consist of isolated particles but that union between a number of these particles takes place to form relatively short fibrils of threads, which intersect one another to form a felt in the irregular meshes of which the mobile liquid phase penetrates. The fibrils in the case of gelatine would, according to Bancroft, consist of a viscous water in gelatine solution, and, according to Hardy, a solid solution of water in gelatine. 

Dispersion in column frits was originally thought to be large and thus, made a significant contribution to the overall extra column variance. It was not until the introduction of low-dispersion unions that it was found that most of the dispersion that was thought to occur in the frits, actually occurred in the unions that contained the frits. Scott and Simpson (11) measured the dispersion that occurred in some commercially available column frits and demonstrated that their contribution to dispersion to be insignificant compared with other sources of extra column dispersion. 

Fig. 24. Dispersive mixing sections for use in single-screw extruders (a) blister ring, (b) Union Carbide mixing section, (c) Egan mixing section, (d) Dray mixing section [148]...

The British had proceeded less expeditiously. The Chiefs of Staff advised in October 1945 that the best defence against atomic bombs was likely to be the deterrent effect that the possession of the means of retaliation would have on a potential aggressor, and in January 1946 they said that a stock in the order of hundreds rather than scores would be necessary to deter a country with widely dispersed industries and population (like the Soviet Union). In December 1945, ministers in the Gen 75 committee approved the construction of the first reactor capable of producing plutonium, and in August 1946 the CAS sent the first requisition for an atomic bomb to the Ministry of Supply. The McMahon Act was amended in October 1950 to allow rather more cooperation between American and British scientists but the first British test did not take place until 3 October 1952, in the hold of a ship off Australia. The first test of a British atomic bomb dropped by an aircraft did not occur until 11 October 1956. 

Makogon (1965) announced the presence of gas hydrates in the permafrost regions of the Soviet Union. Since that time there have been two extreme views of in situ hydrate reserves. In one view, they have been ignored, presumably because they were considered to be too dispersed and difficult to recover, relative to the conventional supply of gas. In the other view, they were thought to be pervasive in all regions of the earth with permafrost (23% of the land mass) and in thermodynamically stable regions of the oceans (90% of the oceans areal extent). With further exploration and production of gas from a hydrate reservoir, a third, more realistic estimate of the hydrate resource has evolved, as the basis for this chapter. 

In the past 40 years and more, investigations into IS have been in three stages. The first, from 1961 to the early 1970s. was a newly established stage and the work was concentrated mainly in the former Soviet Union. Naturally, the target systems were mainly those with gas as the continuous phase, because the concept of IS was originally aimed at transfer enhancement in such systems, while the dispersed phase in IS was gradually extended to include liquid. 

Day, P.R. (1956) Dispersion of a moving salt-water boundary advancing through saturated sand. Trans Amer. Geophys. Union 37, 595-601... 

Creagh, D. C. (1999). X-ray dispersion corrections. The International Union of Crystallography, Dordrecht/Boston/London. 

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