Blooming

Blooming is one of the features that differentiate pigments from dyes. Fluorescent dyes can only be applied in polymers such as plasticized PVC or polyolefins up to a certain concentration limit. Dyes dissolve in these polymers even at ambient temperature, preventing crystallization and thus precluding blooming. The solubility limit at room temperature can only be exceeded if dye concentrations are very high. In that case, blooming may occur. 

Pigment concentration is not the only system-dependent migration determinant the entire composition of the colored medium plays a role. The tendency of plasticized PVC to promote blooming, for instance, depends on a series of para- 

23 and 24 show the mechanisms underlying the dissolution and crystallization processes during manufacture and storage. As above, the example chosen to illustrate this principle is Pigment Red 170 in plasticized PVC [39], 

Transmission spectra were taken immediately after allowing the pigmented samples to cool down to room temperature. Interpretation of the characteristic 570 nm band shows that at 180°C, all of the pigment crystals are dissolved, provided their concentration is small (0.005 and 0.01%, respectively). At 140°C, however, not all crystals are dissolved. Fig. 25 demonstrates that crystallization, taking place inside a sample rather than on its surface, is not completed even after years of storage [39], 

Scanning electron microscopy makes it possible to trace the time curve of blooming on the surface of a plasticized PVC sample [43]. Pigment Yellow 1 develops detectable surface crystals within a period of only a few horns, and the area is densely covered within a day (Fig. 26 a and b). Even a small space may be sufficient for a pigment to develop a variety of apparently different crystalline forms (Fig. 27), although only one crystal modification appears by X-ray diffraction 

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When The Nylons Bloom Again, words by George Marion, Jr. music by Thomas Fats Waller... 

Problems associated with excessive levels of nutrients and unwanted nuisance species have already been mentioned. There are cases in which intentional fertilization is used by aquaculturists in order to produce desirable types of natural food for the species under culture. Examples of this approach include inorganic fertilizer appHcations in ponds to promote phytoplankton and zooplankton blooms that provide food for young fish such as channel catfish, the development of algal mats through fertilization of milkfish ponds, and the use of organic fertilizers (from Hvestock and human excrement) in Chinese carp ponds to encourage the growth of phytoplankton, macrophytes, and benthic invertebrates. In the latter instance, various species of carp with different food habits are stocked to ensure that all of the types of natural foods produced as a result of fertilization are consumed. 

Ethylenebis(tetrabromophthalimide). The additive ethylenebis(tetrabromophthalimide) [41291 -34-3] is prepared from ethylenediamine and tetrabromophthabc anhydride [632-79-1]. It is a specialty product used ia a variety of appHcations. It is used ia engineering thermoplastics and polyolefins because of its thermal stabiUty and resistance to bloom (42). It is used ia styrenic resias because of its uv stabiUty (43). This flame retardant has been shown to be more effective on a contained bromine basis than other brominated flame retardants ia polyolefins (10). 

Oligomeric Flame Retardants. There are several oligomeric flame retardants. The principal advantage claimed for these materials is their resistance to bloom and plate-out. In some cases they are used at levels high enough that the resulting flame-retarded resia should properly be viewed as a polymer blend or alloy. AH of the available oligomeric flame retardants are brominated (Table 6). 

W. L. Bloom, J. L. HoUenbach, and J. A. Morgan, Medical Radiographic Technique, Charles C. Thomas Publishing, Springfield, lU., 1965. 

Liquid food ingredients encapsulated are typically oil-soluble flavors, spices (see Flavors and spices), and vitamins (qv). Even food oils and fats are encapsulated (63). These core materials normally are encapsulated with a water-soluble shell material appHed by spray drying from water, but fat shell formulations are used occasionally. Preferred water-soluble shell materials are gum arabic, modified starch, or blends of these polymers with maltodextrins. Vitamins are encapsulated with 2ero bloom strength gelatin by spray drying. 

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