bluuebunny/crossref_metadata_2025 huggingface dataset:
Pigment Dispersions
Authors: Loebbert Gerd , Sharangpani Anand S. G.
Published: July 2004

A pigment dispersion, which is used to apply color to the surface of the substrate, such as ink film on paper or paint film on a steel surface, is a uniform distribution of very fine pigment. The quality of the dispersion is dependent on variables such as crystal growth, wetting of the pigment, and flushing of the pigment. Equipment used to make pigment dispersions include kneaders and internal mixers, close tolerance mills, high speed fluid energy mills, and sand, bead, and shot mill.

In the construction of a pigment dispersion, variables such as dispersion concentration and compatibility of the carrier are adjusted on the intended final use. Dispersions can be supplied as flushed pigments, chip dispersions, or color concentrates. The primary applications of the pigment dispersions are in the preparation of printing inks, paints and coatings, and plastics. Historically, the printing ink industry has been the leading consumer of pigment dispersions in the United States. Significant changes are expected in the manufacture and composition of pigment dispersions, in response to environmental and safety regulations and increasing public awareness.
Piping Systems
Authors: Handman Stanley E.
Published: July 2004

Many factors must be considered in the design of a piping system. These include the selection of the pipe material based on the design pressure and temperature and the corrosivity of the flowing material; the determination of the pipe size based on fluid mechanical considerations; and the application of valving. The ANSI/ASME B31 Code for Pressure Piping is delineated, with emphasis on the requirements of B31.3, the section covering chemical plant and refinery piping. Included are the mechanical and structural aspects of design; namely, the determination of pipe wall thickness, the design and selection of pipe supports, and the methods for ensuring that the piping has adequate flexibility to accommodate temperature changes and equipment settlement. Safety and environmental considerations are discussed.
Genetic Engineering, Plants
Authors: Edwards Janice W. , Kishore Ganesh M. , Stark David M.
Published: July 2004

JANICEW. EDWARDS, GANESHM. KISHOREand DAVIDM. STARK(Monsanto Company)

Several discoveries in the 1980s and 1990s permitted the transition of plant molecular biology from a fledgling science to commercial reality. These discoveries ranged from the identification of biologically important genes to the development of methods to introduce new genes into plants transformation and regulate gene expression. Nearly five dozen plant species have been transformed and the list of plant species subject to transformation include principal field crops such as corn, cotton, rape, rice, soybean, and wheat. In addition, several horticultural species such as tomato, potato, etc, have been subject to transformation. More than 500 field tests have been conducted and transgenic plants such as transgenic tomato, soybean, corn, rape, etc, are in the advanced stages of commercial development and regulatory process.

Four methods have been extensively investigated for the introduction of transferred deoxyribonucleic acid (T‐DNA) into plants. Most common direct uptake of DNA by protoplasts, particle acceleration techniques such as electrostatic discharge or biolistics gun technology, and DNA uptake into partially digested immature embryos.

Expression of genes that have been introduced into plants is regulated by promoters, although the extent of regulation of gene activity by the promoter is influenced at least to some extent by the insertion site of the gene within the chromosome. The choice of promoters is dictated by the tissue and developmental specificity required for gene expression. Two specific applications of plant biotechnology include engineering tolerance to the widely used herbicide glyphosate, C3H8NO5P, and increasing starch biosynthesis in plants. Both tomato fruit ripening and fruit firmness are among the advanced quality traits that are being investigated.
Plant Layout
Authors: E. Meissner Roland
Published: July 2004

This article discusses the process by which a plant plot plan is developed and the spacing and orientation between equipment. It describes the step‐by‐step procedures which a designer goes through in selecting the arrangement of equipment and providing the necessary space between the equipm ent items. Examples are included that illustrate the concepts presented. The article also presents an evaluation and discussion of the three principle types of layout presentations: orthographic drawings, plastic models, and computer‐aided design models. Practical uses and limitations of each of these presentation mediums are covered. Many practical design tips are included. Sufficient background information is provided for the reader to appreciate the subtleties of plant layout. The piperack design and its use as the arterial system for the plant are also covered.
Plant Safety
Authors: Prugh Richard W.
Published: July 2004

Health and safety of personnel and loss prevention are paramount concerns of the chemical industry. Several industry groups encourage members to improve the management of safety and improve manufacturing procedures and practices to minimize hazards. Moreover, state and federal authorities have legislated improvements for the safety of both employees and the public. Particular emphasis has been given to process safety in the legislation and in industry guidelines, and chemical manufacturers are required to follow detailed steps in ensuring adequate training, comprehensive operating procedures, thorough analysis of processes for hazards and investigation of accidents, diligent maintenance of facilities, well‐developed emergency plans, and self‐audits for compliance. Process safety management, including process production hazards and the various engineering and administrative controls, is discussed. The role of plant location, design and operation of facilities, and hazard prevention are presented, as are safe work practices and hazard analysis.
Plasticizers
Authors: Cadogan David F. , Howick Christopher J.
Published: July 2004

A plasticizer is a substance the addition of which to another material makes that material softer and more flexible. Most often plasticizers are materials which, when added to a polymer, cause an increase in the flexibility and workability, brought about by a decrease in the glass‐transition temperature,

T
g

, of the polymer. The most widely plasticized polymer is poly(vinyl chloride) (PVC) due to its excellent plasticizer compatibility characteristics, and the development of plasticizers closely follows the development of this commodity polymer. This article provides an overview of the important types of plasticizers which exist, and gives details of manufacture and how different production methods and starting materials affect the properties of the plasticizers. The mechanism of action of plasticizers is described, in terms of plasticization theory and the chemical modifications that occur during this process, which account for the excellent performance of some plasticizer molecules and the apparently poor softening ability of others. These effects are used to make products that are familiar to daily life and a change of plasticizer can produce changes in the properties of a wallcovering, a cable sheathing, etc. The current legislative and toxicological status of plasticizers are thoroughly reviewed to provide information about the environmental effects of this widespread use of these products.
Plasma Technology
Authors: Smith Mark D.
Published: July 2004

Plasma can be broadly defined as a state of matter in which a significant number of the atoms and/or molecules are electrically charged or ionized, but the numbers of charges, both negative and positive, are equal. Plasma technology involves the use of these natural or artificially produced plasmas, whether gases, solid, or liquid. Plasmas range in size and density from wisps of interstellar matter to those that exist within the solids used in solid‐state technologies to those that are the unimaginably dense and hot interiors of stars. Plasmas can be as natural as lightning or the aurora borealis, or artificially produced, such as the flashes resulting from thermonuclear fusion experiments. Production of plasmas, modification and possible dissipation, as well as the diagnostics for examining plasmas of various types are included. Differences between gaseous plasmas and plasmas in condensed matter are examined. Uses of plasma include radiation sources, plasma chemistry, chemical analysis, plasma processing, surface modification, plasma polymerization, materials production, energy production, guns and missiles, explosives, weapons, communications, and space travel. Ongoing research in several areas points to a bright future for plasma technology.
Platinum‐Group Metals, Compounds
Authors: Giandomenico Christen M.
Published: July 2004

The platinum‐group metals, ruthenium, osmium, rhodium, iridium, palladium, and platinum, form binary compounds, coordination complexes, and organometallic compounds. Compounds of each of these metals, which exhibit a range of oxidation states, are summarized. Some of the more useful starting materials are noted, as are the most important uses for the compounds of each individual element. There are catalytic applications for the compounds of all six metals; chemotherapeutic applications for platinum compounds; oxidations by ruthenium and osmium compounds; plating and coating uses for platinum and palladium compounds; metal anode applications for iridium and rhodium compounds; and biological applications of ruthenium compounds. The economic aspects of the platinum‐group metal compounds are summarized, as are the most significant health and safety concerns of working with these compounds.
Platinum‐Group Metals
Authors: Seymour Richard J. , O'Farrelly Julia I.
Published: July 2004

The platinum‐group metals, ie, platinum, palladium, rhodium, ruthenium, osmium, and iridium, all have high melting points and exceptional corrosion resistance. Platinum, rhodium, and iridium are particularly stable to oxidation at high temperatures. These metals, especially platinum and palladium, show exceptional catalytic properties.

In nature, platinum‐group metals frequently occur in conjunction with nickel, copper, and iron sulfides. The principal producing region is South Africa, but other commercially important deposits exist in Canada and CIS. In the refining of these metals, solvent extraction technology is increasingly replacing conventional hydrometallurgical processes. Benefits include increased recovery, improved efficiency, and significantly shortened process time. Resources and recovery processes are discussed.

The platinum‐group metals are extensively used as catalysts. Applications include pollution control catalysts for gasoline and diesel vehicles, control of emissions of organics and nitrous oxides from industrial installations, fuel cells and process catalysts in the chemical industry, including nitric acid and chlorine production, and petroleum organic synthesis refining. Platinum‐group metals are also used as jewelry, in the glass industry, in electronic components, in spark plugs, on turbine blades, and in medical devices. Modern cardiovascular surgery and anticancer chemotherapy both employ these metals.
Plutonium and Plutonium Compounds
Authors: Morss Lester R.
Published: July 2004

The discovery of plutonium, its economic and military importance, sources, production, and nuclear properties are reviewed. The economic aspects of weapons‐grade and reactor‐grade plutonium are outlined. The preparation and properties of plutonium metal are discussed in detail. A presentation of the physical and chemical properties of atomic plutonium and stable plutonium ions is given. The complexation and hydrolysis properties of these ions are recapitulated. Analytical chemistry, separations technology, and metallurgy (including pyrometallurgical processing) are described. There is a brief treatment of storage and disposal of excess weapons plutonium. The chemistry of several classes of plutonium compounds is described: oxides, halides, oxyhalides, hydrides, carbides, silicides, nitrides, sulfides, and oxalates. The chapter concludes with a treatment of environmental, health, and safety aspects of plutonium. Vol. 19, pp. 407–443, 197 refs. through September 1, 1995.
Water, Pollution
Authors: Eckenfelder W. Wesley
Published: July 2004

Water is omnipresent on earth, however, the volume of freshwater amounts to one thirtieth of the water of the salty oceans. This article describes the hydrologic parameters involved in storage and transport of freshwater. Water quality management standards, including EPA specified pollutants are identified. Treatment and techniques to control pollution include in‐plant waste control, minimization separations, adsorption, removal of heavy metals and toxic organics are given.
Fluorine‐Containing Polymers, Poly(Vinylidene Fluoride)
Authors: Dohany Julius E.
Published: July 2004

This article reviews the preparation, properties, and uses of poly(vinylidene fluoride) (PVDF or PVF2), including preparation of 1,1‐difluoroethene or vinylidene fluoride (VDF or), and commercially important copolymers of VDF with other fluorinated comonomers. PVDF is commercially produced by free‐radical‐initiated polymerization of VDF in emulsion or suspension. It has the characteristic resistance of fluoropolymers to harsh chemical, thermal, ultraviolet, weathering, and oxidizing environments. PVDF has exceptional resistance to high energy radiation. PVDF has high mechanical and impact strength, and excellent resistance to both creep under long‐term stress and fatigue. Structure and polymorphism of PVDF chains are reviewed. Thermodynamic compatibility of PVDF with other polymers and its solubility are reviewed. Fabrication and processing methods including extrusion, molding, coextrusion, and organosol dispersions are reviewed. Health and safety aspects of PVDF are outlined. Economic aspects of PVDF and cost are discussed. PVDF uses include long‐life exterior architectural finishes, wire and cable uses, fluid handling systems, microporous membranes, and piezoelectric and pyroelectric applications.
Polymethylbenzenes
Authors: Earhart H. W. , Komin Andrew P.
Published: July 2004

Polymethylbenzenes are benzene derivatives that contain three to six methyl group substituents. Included are 1,3,5‐trimethylbenzene (mesitylene), 1,2,4‐trimethylbenzene (pseudocumene), 1,2,3‐trimethylbenzene (hemimellitene), 1,2,4,5‐tetramethylbenzene (durene), 1,2,3,5‐tetramethylbenzene (isodurene), 1,2,3,4‐tetramethylbenzene (prehnitene), pentamethylbenzene, and hexamethylbenzene. Physical properties, chemical properties, manufacture, production and shipping, specifications, health and safety factors, environmental considerations, uses, and derivatives are reviewed. The polymethylbenzenes are primarily basic building blocks for more complex chemical intermediates. Pseudocumene, mesitylene, and durene are used to produce polymer additives and intermediates, antioxidants, and agricultural chemicals.
Polyesters, Thermoplastic
Authors: East Anthony J. , Golder Michael , Makhija Subhash
Published: July 2004

This article covers semicrystalline thermoplastic polyesters and their applications as molding resins. The principal polymers described are PET, PBT, PEN, PCT, thermoplastic elastomers of the PBT–PTMEG‐T type, and liquid crystalline polymers. The raw materials for various polyesters and their production are described and general routes to polyester polymer synthesis outlined. Individual polyesters are described in more detail with particular reference to special features of their polymer chemistry. PET stretch blow‐molded bottles and containers are a very large market and the production of PET bottle resin by continuous polymerization and solid‐state polymerization is described together with an outline of the stretch blow‐molding process. Physical properties, polymer characterization and mechanical properties together with details of polymer injection molding are described.

Particular reference is given to the growing demands for PCT of new electronic and electrical fabrication techniques such as surface mounting technology and its requirements for high temperature polymer properties. PBT polymer is described in detail. Flame‐retardant additives are described and how they affect polymer performance. Safety and health factors for the polymers in use are discussed.

Liquid crystal polymers are relatively new high performance thermoplastics. The nature of the mesophase state and how LCP's differ from conventional materials is described. LCP polymer synthesis is outlined and physical and mechanical properties of several commercial LCP polymers given.
Poly (Vinyl Fluoride)
Authors: Ebnesajjad Sina
Published: July 2004

Homopolymers and copolymers of vinyl fluoride are based on free‐radical polymerization of vinyl fluoride and comonomers, usually under high pressure. Du Pont first commercialized a poly(vinyl fluoride)‐based film in 1961 under the trade name Tedlar. Poly(vinyl fluoride) homopolymers and copolymers have excellent resistance to sunlight degradation, chemical attack, water absorption, and solvent; they have a high solar energy transmittance rate. These properties have resulted in the utilization of poly(vinyl fluoride) (PVF) film and coating in outdoor and indoor functional and decorative applications. These films are used where exceptional high temperature stability, outdoor longevity, stain resistance, adherence, and release properties are required.
Polymers Containing Sulfur, Poly(Phenylene Sulfide)
Authors: Geibel Jon , Leland John
Published: July 2004

Poly(p‐phenylene sulfide) (PPS) is an important industrial thermoplastic material. This article reviews the history, syntheses (both laboratory and commercial), and properties of PPS. Characteristics such as thermal transition, thermal stability, rheology, solution viscometry, size‐exclusion chromatography, UL temperature indexes, mechanical properties, chemical resistance, and electrical properties of neat PPS resin and reinforced PPS compounds, are all discussed. Significant areas where PPS resins are used are presented.
Fibers, Poly(Vinyl Alcohol)
Authors: Hikasa Jun‐ichi
Published: July 2004

Commercial production of poly(vinyl alcohol) fiber started in 1950, 20 years after the inventors of the resin had tried to form it into fiber. PVA fiber is manufactured by wet spinning methods and a dry spinning method. There are variations of the former method which have been developed to improve the quality of the fiber.

Characteristics of PVA fiber are high strength, low elongation, and high modulus. This fiber is also very hygroscopic, has good dimensional stability under dry heat, and has good chemical resistance to various agents. In particular, PVA fiber exhibits high resistance to alkali.

This fiber has been used for clothing and interior applications, but now it is used for various industrial applications because of its superior mechanical properties of high strength and modulus, resistance to chemicals, high durability against uv rays, etc. The main fields of application are in the rubber industry, agriculture, fishing, nonwovens, paper, plastic reinforcement, cement reinforcement, and others.
Polymethine Dyes
Authors: Kachkovski Alexy D.
Published: July 2004

Polymethine dyes (PMDs) encompass a large class of linear, conjugated, colored systems in the general form of\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${{(}{\rm{G^{\pm }_{1}}}{\relbar \kern-5pt{\relbar}\kern-7pt{\relbar}}{\hskip-7pt}{(}{\hskip0.167em}{\rm{CH}}{\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}}{\rm{CH}}{\relbar \kern-5pt{\relbar}\kern-7pt{\relbar}}{\hskip-9pt}{)}_{n}{\rm{CH}}{\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}}{\rm{G_{2}}}{)}{\rm{X^{\mp }}}}$\end{document}, where G1and G2are end groups. In the ground and first excited states, the carbon–carbon bonds within the polymethine chain are practically equalized and alternating positive and negative charges appear at the carbon atoms. The main topological factors affecting PMD color are chain length, nature of end groups, electron shell occupation, asymmetry, chain branching, and chromophore interaction.

Polymethines are highly reactive compounds. Their photochemistry, protonation, and reactions with electrophiles, nucleophiles, reactants, and radicals are surveyed. The most important reason for the extremely wide technical uses of PMD is their low electron‐transition energies. Attention is paid to the application of polymethines as spectral sensitizers, laser dyes, and polymerization initiators. Synthetic methods for obtaining PMDs with various chain lengths, end groups, and chromophore modification are summarized, along with molecular designs and economic aspects.
Polymer Blends
Authors: Keskkula H. , Paul D. R. , Barlow J. W.
Published: July 2004

The physical approach of blending polymers to develop new or improved polymeric products has been an extremely active area of academic and industrial research for nearly three decades, owing to the much higher costs associated with the alternative of chemical synthesis of new polymers. This activity has been paced by the rapid commercialization of products based on blend technology, including polyamide‐, polyester‐, styrenic‐, vinyl‐, acrylic‐, olefinic‐, and epoxy‐ based materials. The basic principles needed to practice this approach are reviewed, including molecular and thermodynamic factors affecting blend‐phase behavior (miscibility or compatibility), phase morphology, processing, interfacial behavior, and chemical reactions that can occur. General trends and examples of physical properties are given, with special emphasis on the important commercial developments, followed by speculations about future developments.
Polymers of Higher Olefins
Authors: Kissin Yury V.
Published: July 2004

The article describes polymeric materials derived from the higher α‐olefins with carbon atom numbers of four or higher as well as polymers of cycloolefins. Crystalline polymers of higher α‐olefins belong to two classes of stereoregular polymers, isotactic and syndiotactic. Isotactic polymers are produced with two types of catalysts, heterogeneous Ziegler‐Natta catalysts and bridged metallocene catalysts. Other metallocene catalysts produce either crystalline syndiotactic polymers or amorphous atactic polymers. Higher α‐olefins can also be polymerized with cationic initiators to amorphous oligomeric materials. Cycloolefins are polymerized by two different mechanisms: the ring‐opening metathesis reaction catalyzed by tungsten or molybdenum compounds, and polymerization reactions without ring opening catalyzed by metallocenes.

Two isotactic polymers of higher α‐olefins, poly(1‐butene) and poly(4‐methyl‐1‐pentene), as well as oligomers of linear α‐olefins and polymers of certain cycloolefins (polydicyclopentadiene, polyoctenamers, and norbornene elastomers) are produced commercially. Crystalline poly(1‐butene) is used to manufacture pipe, tubing, and blown film. Crystalline poly(4‐methyl‐1‐pentene) is a highly transparent plastic used for the manufacture of medical and chemical laboratory equipment as well as a variety of injection‐molded articles. Liquid oligomers of higher linear α‐olefins produced with cationic initiators have found wide applications as base oils in the formulation of various industrial lubricants; among other applications, they are used in synthetic lubricating oils for cars, transformer oils, and transmission and crankcase fluids. Polymers of cyclooctene are mostly used as components in rubber and compositions based on PVC or polystyrene. Cured liquid‐molding resins based on polydicyclopentadiene are used for the manufacture of automotive parts for trucks, snowmobiles, wheel loaders, and recreational vehicles.
Polyimides
Authors: Takekoshi Tohru
Published: July 2004

Polyimides are high performance polymers employed as key materials in advanced industrial applications, including aerospace, electrical, and electronic engineering. Polyimides are capable of functioning at high temperature and in oxidative environments, and have outstanding mechanical strength, excellent electrical properties, and wide ranging chemical resistance. One of the advantageous characteristics of polyimides over other high temperature polymers is their processibility through soluble intermediates. Polyimide polymerization is a thermodynamically driven condensation reaction and can be performed in a simple manner, includingin situpolymerization. It is also a versatile system in terms of synthesizing wide varieties of copolymer compositions for the required properties. In this article, various synthetic methods for polyimides, and properties and applications of principal commercial polyimides, are reviewed. Advances in the chemistry and applications of polyimides are also described.
Polyhydroxyalkanoates
Authors: Tan Irene K. P.
Published: July 2004

Polyhydroxyalkanoates (PHA) occur naturally as water‐insoluble inclusion bodies within the cytoplasm of a variety of bacteria. They have garnered global interest because they have properties similar to petrochemical‐derived plastics, in addition to which they are also biodegradable and biocompatible, and are synthesized from renewable resources. The two main classes, short‐chain‐length PHA (PHASCL) and medium‐chain‐length PHA (PHAMCL), are synthesized in non‐pseudomonads and fluorescent pseudomonads, respectively, along different biosynthetic routes. The production of bacterial PHA by fermentation is well developed, the highest yield being obtained from recombinant strains. Nevertheless, the production cost of PHA is currently many times higher than petrochemical plastics which thus makes PHA economically unviable to be used for bulk commodities. There is, however, much potential for PHA to be used in biomedical applications. Areas of on‐going R&D include improving the fermentation and recovery processes as means to increase PHA yield and reduce processing costs while developing processes that reduce negative impacts on the environment.In vitrobiosynthesis using purified enzymes (eg, PHA synthase) and activated precursors (eg, 4‐hydroxybutyryl‐CoA), and the technology to effectively recycle the enzymes is another area of active study. The development of transgenic plants that produce PHA, like how starch and vegetable oils are produced, is widely believed to hold the key to viable large scale production of PHA at costs that allow the material to be used for common disposable products that are the major plastic pollutants.
Polymers Containing Sulfur, Polysulfides
Authors: Vietti David , Scherrer Micheal
Published: July 2004

Polysulfide elastomers were the first synthetic rubbers made in the United States. They are prepared from simple low cost starting materials and the thiol end group provides a variety of chemical approaches to curing. The most common method is through oxidative coupling. Polysulfides can also be cured with diisocyanates or epoxies. They are commonly used as a flexibilizer and reactive diluent in epoxy formulations. Their unusually good resistance to solvents and to the environment and good low temperature properties have made them particularly useful in sealant applications. They are the standard sealant for virtually all aircraft integral fuel tanks and bodies. Polysulfides are the worldwide market leader in insulating glass sealants and have been used since the 1950s as construction sealants. Polysulfide elastomers' broad spectrum of chemical and solvent resistance and other unique properties make them useful in a variety of specialty rubber applications.
Hormones, Posterior Pituitary Hormones
Authors: Spatola Arno F.
Published: July 2004

Oxytocin and vasopressin are cyclic peptide hormones primarily synthesized in the human hypothalamus and stored in the posterior pituitary. These nonapeptide amides, along with at least 14 other variants found in lower vertebrates and invertebrates, contain cysteine residues at positions 1 and 6, forming a disulfide bridged ring, along with a tripeptide C‐terminal extension. The hormones are stored in neurosecretory granules with their respective carrier proteins, the neurophysins, prior to release into the bloodstream.

Oxytocin promotes milk ejection and uterine contraction; human arginine vasopressin promotes water retention and exerts a pressor effect. Both hormones or their analogues are used clinically and both are being intensively studied for additional physiological effects. These include nurturing behavior in women and penile erection in men for oxytocin, and memory consolidation for arginine vasopressin and analogues.

Receptors, including some receptor subtypes, have been cloned for both hormones. Oxytocin and V1receptors function through the GP/1 phospholipase C complex, whereas V2receptors activate adenosine monophosphatase (AMP). Selective peptide and nonpeptide, ie, peptidomimetic, analogues are being developed that should offer improved therapeutic utility.
Potassium Compounds
Authors: Freilich Mark B. , Petersen Richard L.
Published: July 2004

Water‐soluble salts of potassium, collectively called potash, are important for the manufacture of numerous articles of commerce and for direct application as fertilizers. Other uses of potassium compounds range from use in specialty glass to that of food additives. Potassium chloride, the most commonly used potash and the raw material for the manufacture of most of the other potassium compounds, is principally obtained from the mining of sylvinite. The ore refinement process, which includes crushing, scrubbing, hydraulic desliming, froth flotation, centrifugation, and drying is described. Potassium hydroxide is produced industrially by electrolysis of the chloride. The hydroxide is used for the production of the commercially important potassium carbonate and potassium phosphates. Several processes are used to convert potassium chloride to other potassium compounds such as the sulfate. Potassium magnesium sulfate is also an important fertilizer. Other compounds of commercial importance include the potassium salts of acetate, bromide, bicarbonate, formate, iodide, permanganate, and acid tartrate. Potassium has an essential role for the biochemistry of both plants and animals. Potassium compounds commonly used in fertilizers are not considered to be hazardous; however, potassium may be paired with a poisonous, corrosive, or oxidizing anion and requires special handling.
Coating Processes, Powder Technology
Authors: Richart Douglas S.
Published: July 2004

Methods for applying decorative and protective coatings utilizing finely divided powders followed by heat fusion of the powder particles to form a continuous film are gaining in popularity and commercial acceptance. Since there are no volatile organic compounds present, powder coating is an environmentally friendly, nonpolluting coating process, providing coatings with improved performance as well. Powder coatings can be found on many common items including lawn and garden equipment, outdoor metal furniture, display racks, architectural aluminum panels and trim, and many automotive compounds including the exterior clear coat.

The chemistry and composition of powders used in coatings and their properties are described, as well as their method of manufacture, processes used to apply them, their applications and a review of health, safety and environmental considerations. Over 100 references are supplied to provide more detailed technical information.
Power Generation
Authors: Collins Steven
Published: July 2004

The basic processes and equipment used to generate power, whether mechanical or electrical, have advanced significantly in the twentieth century. Fossil fuel‐fired power plants remain the main sources of power generation, although nuclear fuels provide a large percentage of power worldwide. Power generation facilities harness the thermal energy released during the combustion of fossil fuels or the fission of nuclear ones and convert this thermal energy to electricity for transmission and distribution to users. Predominant fossil fuel plant types include conventional boiler‐based Rankine cycle facilities; engine‐based plants relying on combustion turbines (Brayton cycle) or reciprocating engines (Carnot cycle); and combined‐cycle plants relying on a combination of technologies. The various arrangements of the components, the thermodynamic factors, and the efficiencies of these systems are described. Fuel handling and storage, combustion and process control, water and waste treatment, as well as emissions monitoring and control for fossil fuel‐fired plant operations are discussed. Renewable energy technologies, particularly hydroelectric generation, have also been widely applied and demonstrated. Advanced technologies, such as electrochemical fuel cells, hold promise for the future. Many of the principles related to the operation of conventional fossil fuel‐fired plants are also employed in nuclear stations, waste‐fired plants, and renewable energy facilities.
Regulatory Agencies, Power Generation
Authors: Collins Steven
Published: July 2004

Entities involved in the generation of electric power in the United States are subject to regulation by different state and federal agencies. Numerous regulations and laws are in place to protect the environment and ensure fair business practices, stable energy supply, and consumer protection. This article both summarizes the history of electric utility business and environmental regulations in the United States, and discusses the various policies of and roles played by such keys agencies as the U.S. Federal Energy Regulatory Commission, Nuclear Regulatory Commission, and Occupational Safety and Health Administration.
Pressure Measurement
Authors: Ryans J. L.
Published: July 2004

Pressure measurement spans the range from 1,380 MPa (200,000 psig) and higher to\documentclass{article}\pagestyle{empty}\begin{document}${10^{-10}{\hskip0.167em}{\hskip0.167em}{\rm{Pa}}}$\end{document}, ie, extreme ultrahigh vacuum. Pressure, particularly where it is monitored as opposed to being controlled, is generally measured by mechanical elements. Mechanical pressure gauges are reliable and inexpensive. They dominate process applications in older plants, and the sensing elements for many of the sophisticated electronic transmitters contain simple mechanical elements. The shift away from mechanical sensors to electronic sensors in the chemical process industries is a result of the superior accuracy and reliability of electronic instrumentation. Piezoelectric pressure elements, reluctive pressure transducers, strain gauges, piezoresistive sensors, and capacitive pressure transducers, the principal types of electronic sensors, are described herein. Conventional sensor technology is acceptable for pressure measurement in the low vacuum region, but esoteric technologies developed specifically for high vacuum, eg capacitance manometers, thermal conductivity gauges, and hot and cold cathode ionization gauges, are required for lower pressures. Smart pressure transmitters are revolutionizing industry's approach to pressure measurement. The rationale for replacing conventional transmitters with smart transmitters is discussed herein.
Process Control
Authors: Hahn Juergen , Edgar Thomas F.
Published: July 2004

This article presents the theory and practice of automatic process control and instrumentation, outlining basic concepts of automatic control. The process control hierarchy is described, as is the role played by modern control systems equipment. Because reliable process measurements form the foundation for automatic process control, devices used to measure basic process variables, as well as the practical guidelines for their selections and implementation, are discussed. On‐line process analyzers are also introduced followed by a brief discussion of considerations in the selection and use of final control elements.

An overview of the mathematical principles underlying process control is presented and the most common implementations of single‐loop feedback controllers are described. This is followed by a discussion of more advanced control techniques. Since most control methods can be applied to continuous as well as batch processes, concepts related to batch process control are introduced. In a final section, economic aspects of process instrumentation and control systems are discussed.
Process Integration Technology
Authors: Hallale Nick
Published: July 2004

In the past, the major research emphasis in process design has been placed on the analysis, or simulation of processes. The synthesis of processes or process integration has, in comparison, received little attention. This article will discuss the evolution of process integration technology over the past two decades and outlines the problem of chemical process design and then discusses pinch analysis, which developed against the background of the energy crisis of the late 1970s.

This article will describe the state‐of‐the‐art developments that have been made in process integration and that build on the foundations laid by pinch analysis and mass integration. It will describe how the design tools have evolved from purely graphical, thermodynamic approaches to incorporate the latest mathematical optimization techniques. Process integration can now address four main themes: efficient use of raw materials, energy efficiency, emissions reduction, and process operations.

This article ends by describing some of the issues with industrial applications and describes some very successful case studies before considering some of the future developments that can be expected.
Genetic Engineering, Procedures
Authors: Schmidt Francis J.
Published: July 2004

The contemporary meaning of genetic engineering implies a use of the techniques of molecular biology, especially recombinant deoxyribonucleic acid (DNA) techniques, rather than breeding in the formation of new genotypes. Recombinant DNA molecules are composed of two parts: first, a vector where the function is to provide the biochemical functions necessary for replication of the recombinant DNA molecule, and secondly, the passenger DNA which is joined to the vector and is replicated passively under control of the vector. Recombinant DNA technology allows the constructionin vitroof DNA molecules that are not found in nature and the subsequent introduction into organisms, resulting in new genotypes and phenotypes of the recipient. Particularly in plant and animal science, a gene may be introduced into an organism by recombinant DNA technology and the line with the desired properties further manipulated by breeding. Safety regulations have been modified to recognize that no new hazards are created by recombinant DNA research, eg, DNA introduction does not make a pathogen out of a nonpathogen.
Process Energy Conservation
Authors: Steinmeyer Dan
Published: July 2004

Increased energy conservation comes from broadscale technological progress such as a mix of better hardware, improved catalysts, computer process control, and optimized design. These cause energy efficiency to improve in times of both rising and falling energy prices. In times of rising energy prices, the trade of capital for energy is also important. Principal elements of energy efficient design are optimization of separation systems, including distillation and other techniques; heat‐exchange technology; refrigeration; pressure drop; and steam and condensate systems.

An overall process energy balance serves as a framework during design and after start‐up to optimize energy usage. A more fundamental analysis stresses minimizing the loss of work potential. In separation, efficiency results from low driving forces achieved by multistage processes, hence distillation is dominant. Special separations are usually only economical when removing a relatively dilute component. Heat interchanger capital, together with Δ
T
and Δ
P
costs, dominates many process. Δ
T
has a greater economic impact on the cost of the heat‐exchange surface than does Δ
P
. Methods are given for Δ
T
and Δ
P
selection. Energy efficiency needs to be carefully integrated with the process to maintain reliability and safety.
Polyethers, Propylene Oxide Polymers
Authors: Gagnon Steven D.
Published: July 2004

Propylene oxide and other epoxides under go homopolymerization to form polyethers. In industry the polymerization is started with multifunctional compounds to give a polyether structure having hydroxyl end groups. The hydroxyl end groups are utilized in a polyurethane forming reaction. This article is mainly concerned with propylene oxide and its various homopolymers that are used in the urethane industry.

The polymerization of propylene oxide can be catalyzed by base (used commercially), acid (for glycol synthesis), and by coordination catalysts containing Al, Zn, or Fe as the central atom. The mechanism of base‐catalyzed polymerization is reviewed. The physical properties of poly(propylene oxide) as well as the physical methods for determining them are reviewed. Particular emphasis is placed on nmr which has yielded a wealth of information about the structure of poly(propylene oxide) and copolymers of propylene oxide and ethylene oxide.
Graphite, Properties of Artificial
Authors: Hupp T. R.
Published: July 2004

The graphite crystal, the fundamental building block for manufactured graphite, is one of the most anisotropic bodies known. Anisotropy is the direct result of the layered structure with extremely strong carbon–carbon bonds in the basal plane and weak bonds between planes. Manufactured graphite is semimetallic in character. Conduction is by means of an approximately equal number of electrons and holes that move along the basal planes. Manufactured graphite is strongly diamagnetic. Compared with other refractories, graphite has an unusually high thermal conductivity near room temperature; above room temperature, the conductivity decreases exponentially to approximately 1500°C. The volumetric thermal expansion (VTE) of manufactured graphite is anomalously low when compared to that of the graphite single crystal. The low value of volume expansion of most manufactured graphite has been related to the microporosity within the coke particles. Graphite reacts with oxygen to form CO2and CO, with metals to form carbides, with oxides to form metals and CO, and with many substances to form laminar compounds. Of these reactions, oxidation is the most important to the general use of graphite at high temperatures.
Propellants
Authors: Lindner Victor
Published: July 2004

Propellants are mixtures of chemical compounds that produce large volumes of high temperature gas at controlled, predetermined rates, and can sustain combustion in the absence of atmospheric oxygen. Principle applications are in the launching of projectiles from guns, rockets, and missile systems. Propellant‐actuated devices are used to drive turbines, move pistons, pump fluids, shear bolts and wires, eject pilots and jettison stores from aircraft, and act as a source of heat in special devices. Solid propellants are compact, have a long storage life, and may be handled and used without exceptional precautions.

Propellants, most often based on nitrocellulose, also contain an oxidizer, binder, and sometimes a metallic fuel. Double‐based propellants also have liquid energetic plastizers. Triple‐based propellants contain crystalline additives. Composition, properties, and manufacture of the various propellants are described. Nonconventional propulsion methods are also discussed.
Water, Properties
Authors: Morgan James J. , Stumm Werner
Published: July 2004

The physical‐chemical properties of water as a solvent are tabulated. The magnitude of the main reservoirs and fluxes in the hydrological cycle, with special attention given to the human appropriation of renewable fresh water, are given. The acquisition of solutes in the water is discussed in the context of circulation of water with rocks, atmosphere, and biota, with special attention given to chemical weathering, the biogeochemical cycle, chemical equilibria, and the chemical speciation of the elements.
Biomaterials, Prosthetics, and Biomedical Devices
Authors: Szycher Michael , Qiu Jinhao , Tanaka Mami
Published: July 2004

Prosthetics or biomedical devices are objects which serve as body replacement parts or as tools for implantation of such parts. Such devices are prepared from a variety of materials including metals, plastics, other polymers, and ceramics. Devices for cardiovascular and orthopedic problems are discussed herein as are bioresorbable polymers used for sutures.

Biomedical applications of smart materials can be divided into three categories: (1) implants and stents, such as bone plates and marrow needles; (2) surgical and dental instruments, devices, and fixtures, such as orthodontic fixtures and biopsy forceps; and (3) devices and instruments for medical checkups, such as ultrasonic devices. The applications of the first category require strict biocompatibility of a material because it is implanted in the body for long periods. Among many traditional materials, including metals, alloys, and ceramics, that are available commercially, only a limited number are currently used as prostheses or biomaterials in medicine and dentistry. The applications in the second category require excellent mechanical characteristics as well as biocompatibility. The third category is used mainly for transducers.

Among smart materials, the Ti–Ni shape‐memory alloy (SMA) has attracted the most attention for biomedical applications in the first and second categories due to its excellent biocompatibility and mechanical characteristics. Research on biomedical applications of the SMA started in the 1970s with animal experiments initially, followed by clinical tests. The first example of a successful biomedical application of the SMA was a bone plate, which was used to repair broken bones. Now, many medical and dental applications of SMAs are available, and many new applications are being developed. On the other hand, piezoelectric materials have been widely used as transducers for medical ultrasonic devices due to their sensor function that uses piezoelectricity and the actuator function that uses inverse piezoelectricity.
Proteins
Authors: Nambudripad Raman , Smith Temple F.
Published: July 2004

Nambudripad, Raman (Beth Israel Hospital), and Smith, Temple F. (Boston University). Proteins are biopolymers built up from 20 different amino acids. Their diversity derives from the different combinations of the amino acids which form the sequence. The function of a protein depends on its unique three‐dimensional structure, which is itself determined by the amino acid sequence. The principal forces that drive proteins to their folded structure are the hydrophobic effect and backbone hydrogen bonding. The latter gives rise to the two elements of secondary structure, α‐helix and β‐sheet, commonly observed in proteins. The number of ways that these structures can pack is finite, giving rise to a limited number of folding motifs which recur in proteins of even unrelated structure. The function of proteins is carried out by a few residues in an active site which interacts with other molecules. Prediction of protein structure from its amino acid sequence is an active area of research. Different approaches include energy minimization, comparative modeling, and inverse protein folding. Progress in molecular biology and molecular modeling have made the study of the function and design of proteins a reality.
Pulp Bleaching
Authors: Ni Yonghao , Liu Zhong
Published: July 2004

Pulp fibers currently produced from the pulp and paper industry can be classified into three different kinds: chemical pulps, mechanical pulps, and deinked (recycled) pulps. The principle objective of bleaching any type of pulp is usually to increase the pulp brightness, which is defined as reflectance measured at a wavelength of 457 nm. However, the strategy and detailed processes are different for different pulps. This information is given in this article.