Physical forms

Combinatorial chemistry and parallel synthesis are now the dominant methods of compound synthesis at the lead discovery stage [2]. The method of chemistry synthesis is important because it dictates compound physical form and therefore compound aqueous solubility. As the volume of chemistry synthetic output increases due to combinatorial chemistry and parallel synthesis, there is an increasing probability that resultant chemistry physical form will be amorphous or a neat material of indeterminate solid appearance. There are two major styles of combinatorial chemistry - solid-phase and solution-phase synthesis. There is some uncertainty as to the true relative contribution of each method to chemistry output in the pharmaceutical/biotechnology industry. Published reviews of combinatorial library synthesis suggest that solid-phase synthesis is currently the dominant style contributing to about 80% of combinatorial libraries [3]. In solid-phase synthesis the mode of synthesis dictates that relatively small quantitities of compounds are made. 

Antimicrobials for plastics are usually supplied as a biocide concentrate rather than the pure active ingredient because the safe handling of many of the pure antimicrobial agents requires special precautions for which the typical plastic processor is not equipped. The use of concentrates also helps insure that the relatively low level of the additive is accurately dosed and well dispersed into the plastic during processing. Several products are offered as both liquid solutions or polymer pellet concentrates. 

Solid biocide concentrates have several advantages. They are easier to handle safely and clean up of any spilled material is safer and easier than with liquid products. Also, there are fewer problems with the disposal of empty containers. Some disadvantages to solid biocide pellet concentrates can be incompatibility with some customer formulations and processes. It is more difficult to meter small quantities of solid pellets than liquids and solid biocide pellets tend to be more expensive to use. 

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Another important class of dryer is the fluidized-bed dryers. Some designs combine spray and fluidized-bed dryers. Choice between dryers is usually based on practicalities such as the materials handling characteristics, product decomposition, product physical form (e.g., if a porous granular material is required), etc. Also, dryer efficiency can be used to compare the performance of different dryer designs. This is usually defined as follows -. 

Black Powder. Black powder is mainly used as an igniter for nitrocellulose gun propellant, and to some extent in safety blasting fuse, delay fuses, and in firecrackers. Potassium nitrate black powder (74 wt %, 15.6 wt % carbon, 10.4 wt % sulfur) is used for military appHcations. The slower-burning, less cosdy, and more hygroscopic sodium nitrate black powder (71.0 wt %, 16.5 wt % carbon, 12.5 wt % sulfur) is used industrially. The reaction products of black powder are complex (Table 12) and change with the conditions of initia tion, confinement, and density. The reported thermochemical and performance characteristics vary greatly and depend on the source of material, its physical form, and the method of determination. Typical values are Hsted in Table 13. 

Similar materials are available based on potato starch, eg, PaseUi SA2 which claims DE below 3 and has unique properties based on its amylose—amylopectin ratio pecuhar to potato starch. The product contains only 0.1% proteia and 0.06% fat which helps stabilize dried food mixes compounded with it. Another carbohydrate raw material is waxy-maize starch. Maltodextrias of differeat DE values of 6, 10, and 15, usiag waxy-maize starch, are available (Staley Co.). This product, called Stellar, is offered ia several physical forms such as agglomerates and hoUow spheres, and is prepared by acid modification (49). Maltodextrias based oa com starch are offered with DEs of 5, 10, 15, and 18 as powders or agglomerates (Grain Processing Corp.). 

By approximately 8 weeks after birth, the mminant has developed a fully functional mmen capable of extensive fermentation of feed nutrients (4). The rate of development of the mminal environment depends on the amount of milk consumed by the neonate in relation to its growth requirements, the avadabihty and consumption of readily digestible feedstuffs, and the physical form of the feedstuffs (4). The mmen develops much faster with hay than with milk (36). Concentrates, ie, high cereal grain diets, increase the absorptive surface of the mmen but mminal size and musculature develops much more slowly with a concentrate diet than with a forage diet (4). 

As is evident from the listing in Table 3, the fertilizer manufacturer has a wide array of compounds from which to choose. Final choices of products and processes therefore rest heavily on such other factors as availabiUty and cost of raw materials, economy of processing, safety of product, economy of handling and shipping, acceptabiUty of physical form and physical behavior of the product, and farmer acceptance. 

Physical Properties. The physical form and stabiUty of a fertilizer product is of an importance almost equal to that of its chemical content. Commercial fertilizers of importance include not only soHds, but also fluids, both solutions and suspensions, and even a gas (anhydrous ammonia). 

Terephthahc acid (TA) or dimethyl terephthalate [120-61 -6] (DMT) reacts with ethyleae glycol (2G) to form bis(2-hydroxyethyl) terephthalate [959-26-2] (BHET) which is coadeasatioa polymerized to PET with the elimination of 2G. Moltea polymer is extmded through a die (spinneret) forming filaments that are solidified by air cooling. Combinations of stress, strain, and thermal treatments are appHed to the filaments to orient and crystallize the molecular chains. These steps develop the fiber properties required for specific uses. The two general physical forms of PET fibers are continuous filament and cut staple. 

Compound CAS Registry Number Molecular weight Color Physical form Mp, °C Density, g/cm HjO g/lOOmU Other References... 

Modified ethylene—tetrafluoroethylene copolymers are commercially available ia a variety of physical forms (Table 6) and can be fabricated by conventional thermoplastic techniques. Commercial ETFE resias are marketed ia melt-extmded cubes, that ate sold ia 20-kg bags or 150-kg dmms. In the United States, the 1992 price was 27.9—44.2/kg, depending on volume and grade color concentrates are also available. 

Globally, there is a small number of basic fluorosihcone producers General Electric Co. and Dow Corning Corp. in the United States, ShinEtsu in Japan, and Wacker Chemie in Germany. Prices tend to be about 55—220/kg and higher depending on the physical form and the application. 

Equipment. Equipment and processes for thermal preservation depend on the physical form of the food and its pH. Foods having a pH < 4.5... 

Definitions. In addition to showing varying degrees of chemical purity, limestone assumes a number of widely divergent physical forms, including marble, travertine, chalk, calcareous mad, coral, shell, ooHtes, stalagmites, and stalactites. AH these materials are essentially carbonate rocks of the same approximate chemical composition as conventional limestone (2—4). 

Physical forms Physical size, mm (mesh size) Derivation ... 

The condensed phosphoric acids are hygroscopic and exhibit a variety of physical forms at room temperature. The material appears oily at 72—82 wt % P20 viscous and gummy at 82—90 wt % P2O5 and is a mixture of glassy and crystalline material at 90 wt %. 

Hardness of the aimealed metals covers a wide range. Rhodium (up to 40%), iridium (up to 30%), and mthenium (up to 10%) are often used to harden platinum and palladium whose intrinsic hardness and tensile strength are too low for many intended appHcations. Many of the properties of rhodium and indium. Group 9 metals, are intermediate between those of Group 8 and Group 10. The mechanical and many other properties of the PGMs depend on the physical form, history, and purity of a particular metal sample. For example, electrodeposited platinum is much harder than wrought metal. 

Catalytic properties are dependent on physical form, principally the exposed surface area which is a function of particle size. Industrial PGM catalysts are in the form of finely divided powder, wine, or gauze, or supported on substrates such as carbon or alumina (see Catalysis Catalysts, supported). 

Alkoxide CAS Registry Number Color and physical form mp,°C bp, °C/Pa Solubihty in organic solvents References... 

Name CAS Registry Number Molecular formula Molecular weight Physical form at 25°C Boiling point, Freezing point, °C Density, g/mL Typical Assay Flash point, °C Molten color APHA... 

Common name CAS Registry Number Trade name Manufacturer Physical form Priced /kg... 

Fiber chemistry determines whether the material is an oxide or nonoxide and can also influence its vitreous or polycrystalline physical form. Refractory fibers generally have diameters ranging from submicrometer to 10 )J.m, and lengths, as manufactured, may range from millimeters to continuous filaments. 

Physical Form. Eor compounders, physical form is an important characteristic. They prefer sohd, free-flowing, nondusty materials whereas polymer manufacturers prefer materials that are Hquid and easily emulsified. Undesirable are semicrystalline materials which may stratify during storage. Also, substances to be avoided are highly viscous Hquids and low melting resins which block upon storage. 

Reagent Formula Physical form Cost, /kg Cost for SO3, /kg U.S. mfg U.S. plants... 

Table 22. Physical Form and Solubility of Fatty Acid Diethanolamides...

Fatty acid Amine acid Physical form Water solubiUty... 

The physical form of the thermocouples varies significantly according to appHcations. Most spacecraft power suppHes utilize separate thermocouples that can be checked for performance at successive stages of manufacturing and be replaced if necessary. This approach fits in very well with the extremely high rehabihty requirements imposed on such systems. In terrestrial systems where such individualized attention is not economically feasible, modular assembhes are generally used, which can contain tens to hundreds of couples in a single unit. 

Vinyl ether Physical form Specific viscosity, Trademark Manufacturer Uses... 

The bulk density of cellulose acetate varies with physical form from 160 kg/m (10 lb /ft ) for soft dakes to 481 kg/m (30 lb /fT) for hammer-milled powder, whereas the specific gravity (1.29—1.30), refractive index (1.48), and dielectric constant of most commercial cellulose acetates are similar. 

Chlorinated paraffins vary in their physical form from free-flowing mobile Hquids to highly viscous glassy materials. Chlorination of paraffin wax (C24—C30) to 70% chlorine and above yields the only soHd grades. Physical properties of some commercially available chlorinated paraffins are Hsted in Table 1. 

Nucleation tempering of the stiU molten fat is necessary because the cocoa butter, if left to itself, can soHdify in a number of different physical forms, ie, into an unstable form if cooled rapidly, or into an equally unacceptable super stable form if cooled too slowly, as commonly happens when a chocolate turns gray or white after being left in the sun. The coarse white fat crystals that can form in the slowly cooled center of a very thick piece of chocolate are similarly in a super stable form known in the industry as fat bloom. 

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