Crystallization characteristics

Essentially all the ammonium sulfate fertilizer used in the United States is by-product material. By-product from the acid scmbbing of coke oven gas is one source. A larger source is as by-product ammonium sulfate solution from the production of caprolactam (qv) and acrylonitrile, (qv) which are synthetic fiber intermediates. A third but lesser source is from the ammoniation of spent sulfuric acid from other processes. In the recovery of by-product crystals from each of these sources, the crystallization usually is carried out in steam-heated sa turator—crystallizers. Characteristically, crystallizer product is of a particle size about 90% finer than 16 mesh (ca 1 mm dia), which is too small for satisfactory dry blending with granular fertilizer materials. Crystals of this size are suitable, however, as a feed material to mixed fertilizer granulation plants, and this is the main fertilizer outlet for by-product ammonium sulfate. 

Naphthalenediol. This diol is prepared by the alkah fusion of 2-hydroxynaphthalene-6-sulfonic acid (Schaffer acid) at 290—295°C. Schaffer acid is usually produced by sulfonation of 2-naphthol with the addition of sodium sulfate at 85—105°C. This acid is also used as a coupling component in the production of a2o dyes such as Acid Black 26. 2,6-Naphthalenediol is used as a component in the manufacture of aromatic polyesters which, as is also tme of the corresponding amides, display Hquid crystal characteristics (52). 

Driving force for melt crystallisation is melting point (mp) difference of impurities and desired product feed must meet mp and crystal characteristics for feasibUity (see also solution crystallisation). 

Along with operating variables of the crystallizer, nucleation and growth determine such crystal characteristics as size distribution, purity, and shape or habit. 

Solution and peel properties of polychloroprenes with fast crystallizing characteristics but different molecular weight... 

Particulate crystal characteristics 9 Characteristic chord iength... 

Crystal characteristics eomposition, form, habit, shape faetors, and solid density (Chapter 1). 

Such simplified considerations can only serve as approximations to a more complex problem even the shade of a polycyclic pigment basically depends on crystal characteristics, such as particle size, particle size distribution, and crystal modification. 

Ziabicki and Jericki reported the crystallization characteristics of PET as well as a theory of molecular orientation and oriented crystallization [5a], Besides these theoretical considerations, the rate of recrystallization understandably seems to play an important role, particularly in high-speed spinning. Little is known about the crystallinity gradient caused during melt spinning at high take-up speeds. 

Minnick, L. A., Reinforced molding composition based on poly(l,4-cyclohexylenedimethylene terephthalate) having improved crystallization characteristics, US Patent 4 859 732, 1988. 

The method to inspect the crystallizer characteristics and to estimate the crystallization rate parameters from the characteristics of CSD was presented and shown to be useful, by applying this method to many CSD data of CEC type crystallizer. It was found that there exists a tendency,... 

Liquid crystal polymers (LCP) are polymers that exhibit liquid crystal characteristics either in solution (lyotropic liquid crystal) or in the melt (thermotropic liquid crystal) [Ballauf, 1989 Finkelmann, 1987 Morgan et al., 1987]. We need to define the liquid crystal state before proceeding. Crystalline solids have three-dimensional, long-range ordering of molecules. The molecules are said to be ordered or oriented with respect to their centers of mass and their molecular axes. The physical properties (e.g., refractive index, electrical conductivity, coefficient of thermal expansion) of a wide variety of crystalline substances vary in different directions. Such substances are referred to as anisotropic substances. Substances that have the same properties in all directions are referred to as isotropic substances. For example, liquids that possess no long-range molecular order in any dimension are described as isotropic. 

The lanthanum glasses were not developed until after 1935 and much of the experimentation on improvement of chemical durability and crystallization characteristics was performed during the 1950 s. These glasses have played a big part in overall improvements in many optical systems such as the modern camera. 

Figures 2-5 depict the effects of CL content upon number-average molecular weight, glass transition temperature(Tg) and crystallization characteristics for those copolyesters derived from oligomeric PCL-diols.

Practical use of the solidification and crystallization characteristics of milk lipids has been made in the manufacture of butter which is more easily spread than butter made conventionally. Based on the knowledge that temperature and mechanical manipulation can influence crystallization behavior, various methods of working butter have been devised to produce a softer product (Taylor et al. 1971 Schaap et al. 1981). Another approach has been to separate triglyceride fractions according to solidification or melting ranges and reblend fractions to achieve a softer butter (McGillivray 1972 Black 1975 Frede et al. 1980). 

---