Coatings, dextrins

Lead azide is not readily dead-pressed, ie, pressed to a point where it can no longer be initiated. However, this condition is somewhat dependent on the output of the mixture used to ignite the lead azide and the degree of confinement of the system. Because lead azide is a nonconductor, it may be mixed with flaked graphite to form a conductive mix for use in low energy electric detonators. A number of different types of lead azide have been prepared to improve its handling characteristics and performance and to decrease sensitivity. In addition to the dextrinated lead azide commonly used in the United States, service lead azide, which contains a minimum of 97% lead azide and no protective colloid, is used in the United Kingdom. Other varieties include colloidal lead azide (3—4 pm), poly(vinyl alcohol)-coated lead azide, and British RE) 1333 and RE) 1343 lead azide which is precipitated in the presence of carboxymethyl cellulose (88—92). 

The adhesives (qv) used to form tube seams and bag bottoms include unborated dextrin, borated dextrin, casein, latex—casein, latex, poly(vinyl acetate), vinyl acetate copolymers, and hot-melt materials (10,27). Dextrin and casein adhesives are more commonly used in the production of grocery sacks vinyl acetate-type adhesives are commonly used in ah paper multiwah bags. The hot-melt adhesives are typicahy used to tack the phes of the multiwah bag together and to form the seam and bottom joints when polymer film phes or coated paper phes are used in bag constmction. 

Hydroxyethylstarch is widely used with synthetic latexes in the surface sizing of paper and as a coating binder. For these uses, the hydroxyethylstarch is acid-thinned, oxidized, or dextrinized. Hydroxypropylstarch is used in foods to provide viscosity stabiHty and to ensure water-holding during low temperature storage. 

I. Baussanne, J. M. Benito, C. Ortiz Mellet, J. M. Garcia Fernandez, and J. Defaye, Synthesis and comparative lectin-binding affinity of mannosyl-coated /i-cyclo-dextrin-dendrimer constructs, Chem. Commun. (2000) 1489-1490. 

The next chapter, by Ronald T. Clarke, John H. Coates, and Stephen F. Lincoln (Adelaide) discusses inclusion complexes of the cyclomalto-oligosaccharides (cyclodextrins), a unique group of natural cryptands that has attracted great interest within and outside the carbohydrate fleld in recent years. The article updates the pioneering contribution by Dexter French in Vol. 12 (19S7) on these oligosaccharides, then known as the Schardinger dextrins. 

Charcoal is used as a fuel and burning rate stabiliser while dextrin (starch gum) forms a viscous dispersion in water such that it can be added to the pyrotechnic ingredients to form a slurry that will adhere to the wires when dipped. It is normally necessary to dip the wires several times in order to build up a satisfactory coating before drying in a current of warm air. 

Friction Igniter consists of a primer cup contg a mixt of K chlorate, charcoal and dextrin binder. A loop of wire coated with red phosphorus in shellac extends thru this cup... 

Capillary gas chromatography (GC) using modified cyclodextrins as chiral stationary phases is the preferred method for the separation of volatile enantiomers. Fused-silica capillary columns coated with several alkyl or aryl a-cyclo-dextrin, -cyclodextrin and y-cyclodextrin derivatives are suitable to separate most of the volatile chiral compounds. Multidimensional GC (MDGC)-mass spectrometry (MS) allows the separation of essential oil components on an achiral normal phase column and through heart-cutting techniques, the separated components are led to a chiral column for enantiomeric separation. The mass detector ensures the correct identification of the separated components [73]. Preparative chiral GC is suitable for the isolation of enantiomers [5, 73]. 

It has been applied in expls industry for coating various expls to render them less sensitive. An example is "Dextrinated Lead Azide (DLA), described in Vol 1 of this Encycl, pp A545 R to A548-R md A557-R to A563-L... 

The most efficient colloids are pure Acacia gums. For reasons of economy, mixtures of Acacia gums and dextrin may be used. As in the preparation of concentrates for beverages, the oil phase to be protected will be added to the aqueous phase and the coating will be formed during homogenization. The emulsion will then be dried by atomization with air temperature at the inlet of l60 or 180 C and a powder temperature at the outlet of 85 to 90 C. 

RDX, etc) are too sensitive to be used per se and must be desensitized. For example LA may be desensitized by coating its crysts either with dextrin (See Dextrinated Lead Azide in Vol 1, pp A 46 to A548) or with PVAlc (polyvinyl alcohol) (See Vol 1, p A558-R). It can also be desensitized by controlling the size and shape of its crysts [See Service Lead Azide (Brit) in Vol 1, p A557-R], or by pptg it in colloidal form (See Vol 1, p A558-L)... 

In a typical friction primer for an airplane flare, ignition is secured by pulling a loop of braided wire coated with red phosphorus and shellac through a pellet, made from potassium chlorate (14 parts) and charcoal (1.6 parts), hardened with dextrin (0.3 part). 

M. Pawlowska, Separating anatiomers by HPLC on silica dynamically coated with a chiral stationary phase of permethylated-cyclo-dextrin, Chirality, 5 136 (1991). 

Dextrins are produced by dry heating (roasting) starch in the presence of an acid catalyst. They are produced in a range of viscosity and color specifications. Dextrins are primarily used as adhesives in paper conversion, such as laminating and envelope production. A low-viscosity dextrin is used in Europe as a total chlorine free (TCF) coating binder for application on TCF paper. 

Candy coatings are applied via repeated, successive application of dextrin and sugar solutions, followed by drying. Dextrins and monosubstituted starch hydrolyzates are used in candy coatings because of their clear, appetizing films. In this application, clarity, sheen and reduced cracking are desired. Oxidized waxy maize starches are also used.12 Starch used as an impressionable bed for casting candies is typically dent com starch with several tenths of a percent of mineral oil. The oil causes the starch to retain the imprinted shape for a more precisely formed candy piece. 

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