bluuebunny/crossref_metadata_2025 huggingface dataset:
Vinyl Ether Monomers and Polymers
Authors: Login Robert B.
Published: July 2004

The history of vinyl ether homopolymers has been more involved with the progress of polymer science than in the generation of highly successful commercial products. The reason appears to be economic, as less‐expensive monomers such as acrylic and vinyl ester types have dominated end‐use polymer technologies. Copolymers of methyl vinyl ether, especially with maleic anhydride, continue to be important in personal care and pharmaceutical markets. The polymerization of vinyl ethers, because of the strong electron‐donating oxygen, can be readily accomplished with cationic initiators to produce polymers and copolymers having the potential for significant variety. Only poly(methyl vinyl ether), however, achieved commercial success among the homopolymers, though its commercial importance has faded. Divinyl ethers are emerging as important ingredients in radiation‐cured coatings because they are more insensitive than acrylates to atmospheric oxygen present during cationic polymerization. Copolymers based on methyl vinyl ether/maleic anhydride, easily prepared by free‐radical initiation, continue to hold academic interest. The observation in 1949 that isobutyl vinyl ether can be polymerized with stereoregularity ushered in the stereochemical study of polymers, eventually leading to the development of stereoregular polypropylene. In fact, vinyl ethers were key monomers in the early polymer literature. Academic interest in living cationic polymerization and in the unusual compatibility of poly(methyl vinyl ether) with polystyrene continue to demonstrate that vinyl ether‐containing polymers are still valuable for contemporary interest.
N‐Vinylamide Polymers
Authors: Login Robert B.
Published: July 2004

N‐Vinyl lactams and their corresponding polymers and copolymers have received considerable attention in the academic literature and significant commercial success. However, until recently this interest centered onN‐vinyl pyrrolidinone and its polymers and copolymers.N‐Vinyl caprolactam is now emerging commercially because copolymerization withN‐vinyl pyrrolidinone results in copolymers with high levels of lactam functionality but with controlled hydrophobicity desired in many hair‐fixative products designed to resist drop in high humidity environments. Polyvinylpyrrolidinone (PVP) is a unique water‐soluble polymer that forms lustrous, continuous films on dry‐down that are very adhesive because of hydrogen‐bonding to substrates such as skin and hair. This adhesive characteristic also results in a wide variety of useful applications such as pharmaceutical tablet binding, hot‐melt, and paper adhesive applications. PVP is relatively nontoxic and contributes mildness to formulations. PVP will also complex with a variety of small and large molecules because the pyrrolidinone carbonyl group can accept a proton in the presence of large anions, becoming pseudocationic. In addition, because of lactam polarity where significant charge can appear on the nitrogen and oxygen atoms, it can interact with electron‐rich aromatics. Ligands such as anionic dyes and surfactants or triiodide or phenolic or polynuclear aromatics or polyacids, etc, will interact and complex with PVP. PVPHI3or povidone‐iodine is probably the most successful of these complexes, retaining a reservoir of iodine even in dilute solution, affording fresh germicidal iodine as free iodine is consumed. Cross‐linked PVP or crospovidone can be employed to remove bitter tannins (phenolics) from beer and wine. Dry crospovidone can be compressed because of interhydrogen‐bonding, only to rapidly swell when exposed to moisture. For this reason it has achieved success as a tablet disintegrant.
Vitamin K
Authors: Van Arnum Susan D.
Published: July 2004

A brief history of the vitamin is presented from its early discovery to structural and, finally, stereochemical determination. An overview of synthetic approaches to vitamin K1is discussed. Work by researchers in the late 1930s largely forms the basis of the modern‐day industrial synthesis. Since this early work, industrial research has been directed toward process improvements in the basic methodology. Of particular note is the search for improved condensation catalysts, refinements in the oxidation of the naphthohydroquinone to the naphthoquinone, and more environmentally attractive routes to vitamin K3. In the case of vitamin K3there has been significant work on replacements to the historical chromium reagents. A number of patents on biotechnological approaches to the K vitamins have appeared. A synopsis of this work as well as a review of the biosynthesis is discussed. A brief review of the physiological role of vitamin K is presented. In addition to its well‐understood role in blood coagulation, its specific importance in bone mineralization as well as its general metabolic function are active areas of research.
Vitamin D
Authors: Hirsch Arnold L.
Published: July 2004

Vitamin Ds are a group of secosteroids which are precursors to hormonal substances that control calcium and phosphorus homeostasis and participate in the process of regulation of gene transcription in animals. Animals convert 7‐dehydrocholesterol stored in the skin to vitamin D3upon irradiation by sunlight or obtain supplemental supplies of ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) from dietary sources.

Recent research has elucidated the complicated pathway by which the vitamin D structure is converted to hydroxylated metabolites which serve to control the calcium intestinal absorption and bone mineralization or resorption to maintain calcium blood levels. The metabolites have been implicated in disease states relating to calcium homeostasis, such as rickets, osteomalacia, and other bone diseases. The metabolites have also been shown to function like other steroid hormones to support selective cell differentiation. They have thus been implicated in diseases such as cancer, psoriasis, diabetes, etc.

Vitamin D3is manufactured by the chemical conversion of cholesterol to 7‐dehydrocholesterol. Ultraviolet irradiation of the 7‐dehydrocholesterol produces a mixture of photoisomers. The two active isomers, previtamin D3andcis‐vitamin D3form a 20:80 equilibrium mixture. Vitamin D is best assayed by high performance liquid chromatography.

Vitamin D3is active in all animals, whereas Vitamin D2is active in cattle, horses, swine, and particularly poultry. Pure vitamin D3has a potency of\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}${40\times 10^{6}}$\end{document}international units per gram. It is relatively active in most animals at levels of 40–400 IU per day. Vitamin D3is generally recommended as safe.
Silica, Vitreous Silica
Authors: Sempolinski Daniel R. , Schermerhorn Paul M.
Published: July 2004

Vitreous silica is a high temperature, single‐component glass commercially available in a wide range of purities. It has superior chemical resistance, low thermal expansion, and excellent optical transmission from the uv to the near‐ir. Thermal history and trace contamination can have significant effects on a number of properties, ranging from electrical conductivity to absorption characteristics.

Vitreous silica is the material of choice for a variety of commercial and scientific applications, including tubing and containers for chemical processing, uv‐optical elements, envelope material of mercury vapor lamps, and windows for space vehicles. Vitreous silica's high viscosity, even at its melting point, precludes the use of traditional glass‐forming techniques. Manufacture usually involves specialized methods, such as flame hydrolysis or high temperature sintering in helium or vacuum.
Water‐Soluble Polymers
Authors: Glass J. Edward
Published: July 2004

Water‐soluble polymers find application in a wide variety of areas that include polymers as food sources, plasma substitute, and as diluents in medical prescriptions. Other areas of importance for water‐soluble polymers include detergents, cosmetics, sewage treatment, stabilizing agents in the production of commodity plastics, rheology modifiers in the various processes for petroleum textile, paper, and latex coatings production. This article discusses the general features of polymers that influence their water solubility and solution properties. Carbohydrate polymers, cellulose, synthetics, cationic polymers, inorganic polymers, new commercial polymers, and hydrophobe‐modification polymers are discussed.
Aeration, Water Treatment
Authors: Rajenden Richard
Published: July 2004

Aeration for water treatment, the transfer of oxygen, O2, from air to water, is well‐studied. The basic purpose of aeration, used primarily for the treatment of wastewater, is to improve water quality for subsequent usage. Aeration can bring about the physical removal of taste‐ and odor‐producing substances such as hydrogen sulfide, H2S, and other volatiles as well as the chemical removal of metals (iron, manganese), gases (hydrogen sulfide), and other compounds (organics and inorganics) through oxidation and settling. Additionally, aeration is used extensively for the biological oxidation of both domestic and industrial organic wastes. The function of aeration in a wastewater treatment system is to maintain an aerobic condition. Methods developed to estimate the oxygen demand are biochemical oxygen demand (BOD), chemical oxygen demand (COD), total oxygen demand (TOD), total organic carbon (TOC), and theoretical oxygen demand (ThOD). The oxygen transfer rate for aerators is normally reported at standard conditions. Thus, in order to make meaningful comparisons, the oxygen required for treatment under working or field conditions should be adjusted to standard conditions.
Waxes
Authors: Cottom William P.
Published: July 2004

A review of waxes is provided, including classification, source, composition, production, testing, and applications. Waxes are generally classified according to source, such as natural waxes derived from animals or vegetables; mineral waxes derived from petroleum, coal, and peat; and synthetic waxes derived through polymerization of feedstocks such as ethylene, methylene, and α‐olefins. The composition varies widely among the different classifications. Most of the natural waxes are mixtures with long‐chain alcohols, long‐chain carboxylic acids, and long‐chain esters as the major constituents. Waxes derived from coal and peat are similar, while the petroleum waxes consist almost exclusively of long‐chain hydrocarbons. Petroleum‐derived waxes are produced in massive quantities throughout the world. The synthetic waxes are generally low molecular weight polymers (400 to ca 10,000\documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$\overline{M}$\end{document}n), with ethene polymers being the largest volume product. Since all waxes are fairly complex mixtures, physical properties are often used to describe the products. Uses vary from consumer products such as chewing gum, cosmetics, and candles, to industrial applications such as hot‐melt adhesives for carton sealing, flow modifier for plastic resins, and process additive for suspension polymerization.
Weighing and Proportioning
Authors: Leahy Tom
Published: July 2004

This article presents a broad overview of weighing technologies used in traditional industrial, retail, and laboratory weighing applications, and in proportioning and processing of bulk materials. Basic weighing technologies are discussed, including mechanical, hydraulic, analogue, and digital strain‐gauge load cells, electromagnetic force compensation, and nuclear. Scale performance is discussed, along with the requirements for commercial scales. Factors that affect weighing accuracy are discussed, including variations in gravity, moisture content, temperature, and influences resulting from buoyancy and electrostatic or magnetic disturbances. The most important industrial, retail, and laboratory scales and balances are described. Various weighing methodologies are discussed, including weighing predefined quantities, controlling package weight, continuous weighing and controlling, and material proportioning. Some typical weighing applications are discussed to illustrate the range of scale functionality presently available. Tank and hopper scale design considerations are discussed, including weigh modules, tension and compression arrangements, weigh module capacity, mechanical considerations, scale calibration, feeding and discharge equipment, and indicators and controllers.
Wood‐Based Composites and Laminates
Authors: Lehmann William F.
Published: July 2004

The pioneers and settlers of America found forests which seemed to go on forever. The forests provided low cost building materials and shelter in those times and continued to do so on through the industrial revolution and up to the present day. Thanks to the foresight of a few foresters and politicians in the 1900 era, vast forestlands across the country were set aside on a multiple‐use basis; an important precept of which was to provide a sustained and renewable timber harvest to bolster the nation's need for wood and wood products. Properly managed, these lands and those of private landowners can supply these needs indefinitely.

The wood resources also must be utilized effectively, so that the various wood products and papers will continue to be available in the necessary quantities at reasonable cost. Practices which better utilize smaller trees and wood residues, which were formerly wasted, to create useful composite materials are an extremely important segment of this entire system.

The wood composites industries in the United States have grown steadily for approximately 100 years. Product development has grown into production of a family of composites which can fill virtually every niche in the construction field, in furniture and cabinetry, as well as in numerous other applications for these products. The industry began with hardwood plywoods and has progressed through softwood plywood, insulation boards, hardboards, particleboards, medium‐density fiberboards, waferboards and oriented strand boards, and finally structural composite lumber. From their beginnings, these products have filled needs in applications to which they were well suited. Some later arrivals have competed with earlier products and in some cases have partially or totally displaced them because they were more suited to the application or more economical, or sometimes both. Whereas it may not yet be totally practical, it is possible to build and furnish entire structures such as homes and businesses using only products from the wood composites group.

As the United States begins to rely more heavily on use of smaller trees for construction materials, the products from the composite industries form a most important portion of the country's needs for these products. As an example of the size of these industries, in 1994 wood‐based composite products made with small logs, wood veneer, chips, shavings, and sawdust were produced at a level of 39.1 × 10
6
m
3
.

Primarily owing to availability of economical wood products and building practices which utilize these products efficiently in warm, comfortable, and affordable housing, the United States is possibly the best housed nation on Earth.
Wool
Authors: Naughtin Patrick T. , Huson Mickey G. , Bateup Brett O. , Jones Francis W. , Christoe John R. , Jones Les N. , De Boos Allan G. , Millington Keith R. , Denning Ron J. , Phillips David G. , Evans David J. , Pierlot Tony J. , Guise G. Bruce , Rippon John A. , Harrowfield Barry V. , Rottenbury Rob A. , Humphries Bill , Russell Ian M.
Published: July 2004

Wool is unique among clothing fibers; it is not only the oldest, it is also the only fiber to have been used continuously and universally. The relative importance of wool as a textile fiber has declined as synthetic fibers are increasingly used in textile production. This article discusses raw wool specifications, fiber growth, and morphology, physical and chemical properties, processing, spinning, and dyeing.
Copper Alloys, Wrought
Authors: Caron Ronald N. , Robinson Peter W.
Published: July 2004

The mechanical and physical properties of wrought copper and wrought copper alloys are surveyed according to alloy composition and the temper to which the alloys are processed. Properties important for manufacturing include: formability (bending, drawing, and springback) joining (welding, brazing, and soldering) machinability, and resistances to softening and hydrogen embrittlement. Properties relating to performance of manufactured products are strength, electrical and thermal conductivities, solderability, and resistances to stress relaxation, fatigue failure, and corrosion.

Alloy designations are defined and tensile properties of alloys within the several compositional groups are provided. Wrought copper (99.3% minimum copper); the high coppers (no < 96% copper); zinc and tin brasses; tin, aluminum, and silicon bronzes; specially modified copper–zinc alloys; copper nickels; and nickel silvers are discussed together with the several commercially available precipitation hardenable alloys that are distributed among the compositional groupings. Selected applications and the relative costs of commercial alloys are discussed.
Xanthates
Authors: Harris Guy H.
Published: July 2004

The nomenclature of the xanthates and their derivatives is given. The various physical properties are covered. The recent pKavalues for ethyl xanthic acid are 2.20 or 1.43 and are in agreement with earlier reported values. The alkali metal xanthates decompose on heating or in aqueous solution. The decomposition in aqueous solution has been well studied. The thermal decomposition produces carbonyl sulfide, carbon disulfide, thiols, organic sulfides and disulfides, as well as aldehydes. The solubility of xanthate salts in water and organic solvents is given. The chemical reactions of the xanthates and their esters lead to decomposition products or new derivatives.

The methods of the manufacture of the commercial xanthates is covered. The current estimated number of xanthate plants worldwide is fifteen, and they produced 55,000 metric tons of product in 1995. Production standards are briefly discussed. Various column chromatographic methods were employed to separate the various xanthates and the separated species were detected spectroscopically at a wavelength of 305 nm.

Discussion of the health, safety, and toxicological concerns regarding the commercial xanthates showed that with proper care the xanthates and derivatives can be safely used and handled.

Although the principal use of the alkali metal xanthates and derivatives is in the mining industry, other derivatives find use in rubber compounding. Standards set by the U.S. Food and Drug Administration for the use of chemical in rubber processing and compounding (1996) included zinc butyl xanthate, ethyl and butyl dixanthogen, and a mixture of diisopropyl xanthogen disulfides. A unique use of the alkali metal xanthates is in the removal of metallic mercury from contaminated industrial land sites. The principal derivatives in use (mineral processing) are four types: dixanthogens, xanthogen formates, dialkylthionocarbamates, and theS‐alkyl esters.
X‐Ray Technology
Authors: Sparks Robert A.
Published: July 2004

Analytical x‐ray instruments are used to characterize materials in several ways. There are analytical instruments that can produce images of the internal structure of objects that are opaque to visible light. There are instruments used to determine chemical composition of an object, the crystalline phases of solids, and the complete atomic and molecular structure of a single crystal. The determination of particle size, structural information for fibers and polymers and the study of stress, texture, and thin films are applications that are growing in importance and can be examined with x‐ray instruments. This article gives information on the characterization, generation, and properties of X‐Rays, and principles of x‐ray diffraction.

Small molecule and macromolecule single‐crystal structure determinations are discussed. These techniques are compared with powder diffraction. X‐ray reflectometers, position sensitive detectors, and area detectors are some of the special instruments designed to measure properties of the new and exotic materials being manufactured. Details on x‐ray fluorescence spectrometry and x‐ray radiography are also given.
Fluorine Compounds, Inorganic, Zinc
Authors: Lindahl Charles B. , Mahmood Tariq
Published: July 2004

Zinc fluoride, its hydrate, and various fluorozincates exist. Anhydrous zinc fluoride is a white solid with mp 872–910C. It is prepared from zinc fluoride tetrahydrate in a stream of hydrogen fluoride. Zinc fluoride is used as a mild fluorinating agent in the replacement of chlorine in halogenated hydrocarbons, in fluorophosphate and fluoride glass, and in the manufacture of fluoride glass optical fibers and optical transmitting glass. Alkali/metal fluorozincates are used as catalysts for dental impressions.
Zone Refining
Authors: Wilcox William R.
Published: July 2004

Zone refining is one of a class of techniques known as fractional solidification in which separation is brought about by crystallization of a melt without solvent being added. Zone refining was developed in response to the need for extremely pure germanium. It can be applied to almost every type of substance that can be melted and solidified. Early zone refining theory (progressive freezing, zone melting, nonideal separations, and optimization) are discussed. Equipment and techniques such as types of containers used, drive mechanisms, heating and cooling, floating‐zone melting, and stirring are discussed in detail.
Polylactides
Authors: Degée Philippe , Dubois Philippe
Published: July 2004

This article focuses on the controlled synthesis and properties of polylactide (PLA) in regard to its microstructure and the design of new related materials, with particular attention on nanocomposites built up from PLA and organoclays, ie, organo‐modified layered silicates (OMLS). As far as the ring‐opening polymerization of lactide is concerned, the selectivity and stereoelectivity of novel (catalytic) initiating systems are discussed using different combinations of lactide isomers, catalysts–initiators, and ligands. A series of biodegradable PLA/OMLS nanocomposites prepared by either solution mixing, melt intercalation, orin situintercalative polymerization is described. All these nanocomposites exhibit dramatic improvements in mechanical and many other materials key‐properties as compared with those of unfilled pristine PLA. These improvements include flexural and thermal properties, heat distortion temperature, oxygen permeability barrier, and rate of crystallization. The future of PLA‐based materials is also discussed with special attention to the environmental impact.
Cellulose Esters, Organic
Authors: Edgar Kevin J.
Published: July 2004

Cellulose is one of nature's most abundant structural materials, providing the primary framework of most plants. For industrial purposes cellulose is derived from two primary sources, cotton linters and wood pulp. Cellulose esters are commonly derived from natural cellulose by reaction with organic acids, anhydrides, or acid chlorides. Cellulose esters of almost any organic acid can be prepared, but because of practical limitations esters of acids containing more than four carbon atoms have not achieved commercial significance. Cellulose acetate is the most important organic ester because of its broad application in fibers and plastics; it is prepared in multi‐ton quantities with degrees of substitution (DS) ranging from that of hydrolyzed, water‐soluble monoacetates to those of fully substituted triacetate. Although cellulose acetate remains the most widely used organic ester of cellulose, its usefulness is restricted by its moisture sensitivity, limited compatibility with other synthetic resins, and relatively higher processing temperature. Cellulose esters of higher aliphatic acids, C3and C4, circumvent these shortcomings with varying degrees of success. Mixed cellulose esters containing acetate and either the propionate or butyrate moieties are produced commercially in large quantities by Eastman Chemical Co. in the United States. The properties, manufacturing methods, uses, economics, and safety of organic esters of cellulose are discussed.
Chloroprene Polymers
Authors: Glenn Furman E.
Published: July 2004

Polychloroprene has been in commercial use for over 60 years, but continues to be the elastomer of choice for dynamic applications requiring moderate heat and oil resistance, or where long‐term environmental resistance is required. The material is manufactured by emulsion polymerization of 2‐chloro‐1,3‐butadiene. The properties of the product can be optimized for specific end used by selection of polymerization conditions, by use of comonomers such as 2,3‐dichlorobutadiene and methacrylic acid, and by choice of the method used to control molecular weight. The kinetics of the polymerization process and the structure of the polymer have been studied in detail and related to polymer properties. Commercial products vary widely in properties depending on the intended end use and the details of the manufacturing process. Tough crystalline or ionomeric polymers are preferred for adhesive applications, whereas softer, more flexible polymers are preferred for mechanical goods applications. The latter polymers may be compounded and fabricated by substantially all the techniques used for manufacture of rubber goods by molding, extrusion, or calendering operations. Latexes are used for various bonding and adhesive applications as well as for dipped goods requiring toughness in the unreinforced film.
Colloids
Authors: Schramm Laurier L.
Published: July 2004

Acolloidcomprisesa collection of small particles, droplets, or bubbles of one phase having at least one dimension between ∼1 and 1000 nm, and dispersed in a second phase. Either or both phases may be in gas, liquid, solid, or supercritical phase states. Another property that distinguishes colloidal dispersions is the extremely large area of the interface between the two phases compared with the mass of the dispersed phase. A consequence is that any chemical and physical phenomena that depend on the existence of an interface become very prominent in colloidal dispersions. Colloidal systems are important because they feature prominently, in both desirable and undesirable contexts, in a wide variety of practical disciplines, products, and industrial processes. The problems associated with colloids are usually interdisciplinary in nature, and a broad scientific base is required to understand them completely. This article provides an introduction to the field of colloids, emphasizing the wide range of practical and industrial applications.
Composite Materials
Authors: D'Amore Alberto , Zarrelli Mauro
Published: July 2004

The manufacturing of reliable and high quality composite parts requires the optimization of processing parameters. This article addresses the issue of understanding how polymer composite matrix properties develop during the manufacturing process and how they can be modelled and predicted. The optimized selection of pertinent processing parameters (time, temperature, and pressure) can dramatically increase cost‐effective manufacture of composite parts. It can also be a powerful tool to reduce phenomena such as warpage, residual stresses, microcracking and fiber/matrix failures, which strongly affect the performances and the integrity of the final product. However, process modelling of composite polymer‐based matrices is difficult, mainly because of the dramatic properties change and the complex interaction occurring among the properties during the manufacturing process.

Mechanical tests for advanced composite materials conform in many respects to the conventional test typology used for traditional isotropic materials. Despite the complication associated with the heterogeneity of composite systems, the interface between fiber and matrix, and the anisotropy at micro‐ and macroscopic levels, the same characteristic property definitions generally used for conventional materials can be identified for these novel materials. In some cases additional constants are required and some differences in nomenclature are introduced specially when no isotropic counterpart exists. The evolution of test methods to meet new demands has continued over the years. This article reviews those mechanical test methods that have achieved a well‐established general consensus.
Copolymerization
Authors: Barner‐Kowollik Christopher , Coote Michelle L. , Davis Thomas P. , Matyjaszewski Krzysztof , Vana Philipp
Published: July 2004

This article is primarily concerned with chain copolymerization. Chain copolymerization is important as it allows a wide array of functional molecules to be designed and incorporated into polymeric materials. The article starts with a general description of free‐radical copolymerization and the models that have been applied to facilitate mechanistic understanding. In recent years it has become evident that the reaction mechanism involved in free‐radical copolymerization propagation is appreciably more complicated than originally postulated in the terminal model developed back in the 1940s. For the simple prediction of composition the terminal model, although fairly crude, provides an adequate method in many instances. However, problems arise when it is used to study absolute rate coefficients (cross‐propagation rate coefficients) or when it is used to predict other quantities such as average propagation rates or sequence distribution. After consideration of copolymerization models, the article progresses to discuss the newly emerging field of controlled/living radical copolymerization, and the novel materials that can be made using these highly versatile synthetic methods. There is brief coverage of ionic chain copolymerization and cross‐linking copolymerization.
Epoxy Resins
Authors: Pham Ha Q. , Marks Maurice J.
Published: July 2004

Epoxy resins are reactive intermediates used to produce a versatile class of thermosetting polymers. They are characterized by the presence of a three‐membered cyclic ether group commonly referred to as an epoxy group, 1,2‐epoxide, or oxirane. The most widely used epoxy resins are diglycidyl ethers of bisphenol A derived from bisphenol A and epichlorohydrin. The outstanding performance characteristics of the thermosets derived from bisphenol A epoxies are largely conveyed by the bisphenol A moiety (toughness, rigidity, and elevated temperature performance), the ether linkages (chemical resistance), and the hydroxyl and epoxy groups (adhesive agents). In addition to bisphenol A, other starting materials such as aliphatic glycols and both phenol ando‐cresol novolacs are used to produce specialty resins. Epoxy resins may also include epoxide‐bearing compounds based on aromatic amine, triazine, and cycloaliphatic backbones.

A variety of reagents have been described for converting the liquid and solid epoxy resins to the cured state, which is necessary for the development of the ultimate end‐use properties. The curing agents or hardeners are categorized as either catalytic or coreactive. Catalytic curing agents initiate resin homopolymerization, either cationic or anionic, as a consequence of using a Lewis acid or base in the curing process. Coreactive curing agents are polyfunctional compounds typically possessing active hydrogens that are employed up to stoichiometric quantities with epoxy resins. The important classes of coreactive curing agents include multifunctional amines and their amide derivatives, polyphenols, polymeric thiols, polycarboxylic acids, anhydrides, phenol–formaldehyde novolacs and resoles, and amino–formaldehyde resins.

The largest single use of epoxy resins is in the protective coatings market where high corrosion resistance and adhesion to substrates are important. Epoxies have gained wide acceptance in protective coatings and in electrical and structural applications because of their exceptional combination of properties such as toughness, adhesion, chemical and thermal resistance, and good electrical properties.
Fillers
Authors: Tsou Andy H. , Waddell Walter H.
Published: July 2004

Fillers are particulate materials added to polymers in order to improve the physical properties and/or to reduce the cost of the composite. They can be classified according to their source, function, composition, and/or morphology. No single classification scheme is entirely adequate because of the overlap and ambiguity of these categories. The chemical composition and its effect on composite physical properties typically classify fillers into three broad categories: nonreinforcing or degrading, semireinforcing or extending, and reinforcing fillers. Use of fillers in many commerical polymers is for the enhancement in stiffness, strength, dimensional stability, toughness, heat distortion temperature, damping, impermeability, and cost reduction, although not all of these desirable features are found in any single filled polymer. Improvements in composite physical properties is directly related to particle size, whereby the smaller particulate fillers impart greater reinforcement. Particle‐size distribution and particle shape also have significant effects on composite reinforcement. Filler structure ranges from precise geometrical forms, such as spheres, hexagonal plates, or short fibers, to irregular masses. A particle with a high aspect ratio has higher reinforcement than a more spherical one. Fillers having a broad particle‐size distribution have better packing in the polymer matrix and provide lower viscosity than that provided by an equal volume of the filler with a narrow particle‐size distribution. The properties of particulate‐filled polymers are determined by the properties of the components, by the shape of the filler phase, by the morphology of the system, and by the polymer‐filler interfacial interactions.
Genetic Methods of Polymer Synthesis
Authors: Kiick Kristi L.
Published: July 2004

Genetic methods of polymer synthesis have become an increasingly prominent strategy for the synthesis of well‐controlled polymer architectures. The exact control of molecular weight and sequence of protein biosynthesis permits the production of protein‐based polymers in which functional group placement can be controlled on the angstrom length scale and for which hierarchical assembly affords structural control on the macroscopic length scale. Protein polymers, produced via protein engineering strategies, have captured many of the sequence, structural, and functional properties of naturally occurring structural proteins such as silk, collagen, and elastin. Artificial proteins with sequences designedde novohave also been shown to form well‐controlled lamellar crystalline structures, liquid crystalline phases, and reversible hydrogels. The incorporation of nonnatural amino acids into protein polymers has further expanded their chemical versatility; appropriate engineering of the protein expression host permits the incorporation of alkenes, alkynes, azides, ketones, aryl halides, and other functional groups. The strategies permit the production of polymers for research and commercial applications including drug delivery, vascular graft engineering, tissue engineering, and high performance materials.
Molecular Weight Determination
Authors: Cooper Anthony R.
Published: July 2004

Methods to determine molecular weight averages and distributions of polymeric and oligomeric materials have been devised and developed over many decades. Most of the early classical techniques were primary methods which usually yield only a single molecular weight average, based on theory and measurable constants. Of the classical methods only ultracentrifugation can determine a molecular weight distribution. Secondary methods, which depend on the availability of calibration materials, have largely supplanted the older classical techniques. Methods based on fractionation, with molecular weight characterization of the fractions, or chromatography, with continuous determination of molecular weight, are currently used to generate molecular weight distributions. Newer methods based on dynamic light scattering and viscoelastic measurements are available to determine the molecular weight distribution of difficulty soluble materials. Development of methods to describe the molecular weight and compositional distribution of multimer polymers continues to be a vibrant research area.
Neutron Scattering
Authors: Dadmun Mark D.
Published: July 2004

Analysis of the scattering patterns of neutrons from soft materials is a powerful technique that provides information on the structure and dynamics of large‐scale structures such as polymers, proteins, colloids, and biological complexes. Moreover, the ability to selectively highlight a macromolecule by selectively deuterating it provides a unique ability of neutrons to examine macromolecules in dilute and concentrated solutions as well as melts. In this article, the methods of correlating the structure of a scattering sample to the measured neutron scattering pattern is overviewed to provide a fundamental understanding of the use of neutron scattering to examine soft materials, while advantages and limitations of the technique are also raised. Finally, a series of examples where scientists have utilized neutron scattering to examine the structure and thermodynamics of polymeric and biological molecules are presented, with the hope that this introduction will provide the reader with the information needed to consider the use of neutron scattering in their own research.
Nonwoven Fabrics, Spunbonded
Authors: Smorada Ronald S.
Published: July 2004

Spunbonded fabrics are distinguished from other nonwovens by the integration of fiber spinning, web formation, and bonding during manufacture. Spun bonding is an especially efficient method of manufacturing lightweight fabrics, although the sophisticated manufacturing equipment requires significant capital investment. The thermoplastic polymers, polypropylene, polyester, and polyethylene, provide the material base for most of the fabrics produced. Spinning is accomplished by extruding fibers from either multiple spinnerette banks or a wide rectilinear spinnerette onto a rapidly moving porous belt. Fibers deposited onto the belt form an unbonded web that then passes through a bonder, typically thermal in nature. This process bonds some of the fibers to neighboring fibers, thus providing integrity to the sheet structure. Spunbonded fabrics are produced at widths of 3 m or more in order to facilitate productivity. The high speed manufacture of wide‐width, lightweight fabrics of uniform appearance and properties presents many technical problems. The loss of fiber output from just one of the spinnerettes can cause defects which reduce the usable width of the fabrics. The directionality of the fibers within the fabrics can be controlled during the web‐forming process. This action permits specific physical properties to be engineered into the fabric, although the majority of spunbonded fabrics are, by design, quite isotropic in character. Spunbonded fabrics are used in many applications, including diaper coverstock, interlinings, wipes, furniture construction, geotextiles, carpet backing, mailing envelopes, and filtration. Spunbonded fabrics are routinely used as components in complex structures that utilize their unique physical properties. The enormous growth of spunbonded fabric sales since the 1960s is indicative of their usefulness.
Nuclear Magnetic Resonance
Authors: Demco D. E. , Blümich B.
Published: July 2004

This article presents the basic principles of nuclear magnetic resonance (NMR) and the application of NMR techniques to polymer problems. This includes one‐dimensional NMR studies of molecular motions and dynamic order, studies of viscoelastic polymers by two‐dimensional NMR spectroscopy, and NMR imaging methods. The emphasis is on studies of viscoelastic polymers for which NMR can provide information on such important areas as the chain dynamics in elastomers, the local structure, residual couplings (induced by chemical cross‐links and topological constraints), dynamic order parameters, internuclear distances, intermolecular interactions (which are important for instance for the miscibility), the effects of fillers on molecular motions, and segmental orientation under mechanical stress and others.
Olefin Fibers
Authors: Wust Carl J. , Gammelgaard Erik Grann
Published: July 2004

Olefin fibers, also known as polyolefin fibers, are synthetic fibers of strong commercial importance. Several olefin polymers are capable of forming fibers, but only polypropylene and polyethylene are of practical importance. From the first commercial application of polyethylene in automobile seat covers to multicomponent extrusion for specialty applications, olefin fibers have made a significant impact in the fiber industry. This article reviews the fiber properties, including physical, tensile, chemical, and thermal and ultraviolet stability, which make them ideally suited for these varied applications. Commercial fiber manufacturing and processing is discussed for staple fiber, continuous filament, and directly formed nonwovens. The extrusion, quench, and draw play integral roles in the development of the fiber properties. Bicomponent, high strength, and hard‐elastic fiber technologies are examined.
Oxidative Polymerization
Authors: Higashimura Hideyuki , Kobayashi Shiro
Published: July 2004

This article discusses oxidative polymerizations of aromatic compounds such as phenol, aniline, diphenyl disulfide, benzene, pyrrole, thiophene, and their derivatives, focusing on the reaction mechanism and coupling selectivity. Some of the properties of polymers synthesized by this method, such as, poly(phenylene oxide)s, polyphenols, polyanilines, poly(phenylene sulfide)s, polyphenylenes, polypyrroles, and polythiophenes, are also described.
Polyethers, Aromatic
Authors: Yeager Gary
Published: July 2004

The aromatic polyethers described in this article are engineering thermoplastics which have excellent physical properties and desirable high temperature properties. Two general classes of materials are described. One class of polyethers comprises polymers with only arylene ether linkages in the backbone, ie, the 1,4‐polyphenylene oxides. The principal commercial material, poly(2,6-dimethyl-1,4-phenylene oxide) is prepared by oxidative coupling polymerization of 2,6-dimethylphenol. Its synthesis, reaction mechanism, and properties are described. In addition, compatible blends of poly(phenylene oxides) with polymers such as polystyrene, as well as other types of blends, are mentioned. A second general class of aromatic polyethers that is covered consists of materials containing alternating sequences of polyarylene ethers and other arylene units which are linked by functional groups other than ethers. The latter group includes the commercial materials: polyethersulfones, polyetherketones, and polyetherimides. Syntheses and properties of these are presented.
Propylene Polymers
Authors: Lieberman Richard , Stewart Constantine
Published: July 2004

Polypropylene is one of the most widely used thermoplastics, accounting for one sixth of total consumption of polymeric materials. Many automobiles, textiles, appliances, and other everyday items contain substantial amounts of these polymers. The ability to manufacture a broad variety of polypropylenes having properties tailored for specific applications is the primary factor in its widespread use. Polypropylene is a polymer whose stereoregularity can be controlled, and it exhibits a spectrum of structural variations, because of the ability to control the manner in which the asymmetrum monomer is incorporated into the growing chain, and through the use of comonomers, usually ethylene, which is often used to provide impact‐modified or lower melting polymers. The types of polymers produced, chain‐structural parameters which can be varied and means to characterize them, morophology, thermodynamic properties, processing methods, end use properties, and applications are discussed.

Highly stereoselective Ziegler–Natta catalyst are primarily used to produce polypropylene and are the basis for most modern propylene polymerization processes. The historical development of these catalysts, from the early TiCl3systems to the modern, high yield MgCl2‐supported systems, including proposed polymerization mechanisms, are discussed. These catalysts enabled the evolution of these polymerization processes from the early slurry process to the current liquid monomer or gas‐phase processes. Metallocene catalysts have increasingly been an area of emphasis and have provided further commerical advances recently. Most major polymerization process in use today are discussed, with the most notable being the Spheripol and Unipol process. Key input into these polypropylene technologies and economics are the technology and infrastructure associated with propylene monomer. The large expansion in polypropylene production in the late 1980s was facilitated by the availability of this newer, less costly polymerization technology. This expansion, well in excess of growth in consumption, caused a dramatic reduction in polypropylene prices in the 1990s, most dramatically in the Far East, where few polypropylene plants existed outside Japan before 1985. Current economic prospects and associated industry trends are discussed.
Rubber Chemicals
Authors: Cohen Martin P. , D'Sidocky Richard M.
Published: July 2004

This article presents recent developments in the field of rubber chemicals, including non‐nitrosamine curatives, reversion‐resistance curatives, silica‐to‐rubber coupling agents, and nonstaining and persistent antidegradants for enhanced performance.

Rubber processing chemicals are used extensively to impart performance and processability to rubber products. The rubber compound is described as a mixture of one or more rubber polymers (elastomers) with a combination of fillers, oils, and rubber chemicals. The compound, once vulcanized, provides technologically useful properties, such as may be applied to tires, hoses, belts, tracks, and a variety of mechanical goods.

Vulcanization systems and antidegradants are dominant the classes of rubber chemicals because the largest class of rubbers used in the industry (the so‐called general‐purpose rubbers) require cross‐linking by sulfur or other curatives to provide meaningful performance, and require protection from oxygen and ozone to provide meaningful service lifetimes.
Solid‐State Extrusion
Authors: Beygelzimer Y. E. , Beloshenko V. A.
Published: July 2004

Solid‐state extrusion (SSE) is a method for attaining a highly oriented state of polymers, and is based on polymer deformation at temperatures just below the polymer melting temperature, or for amorphous polymers just above the glass‐transition temperature mainly by extrusion through conical or slit dies.

SSE is used for shape forming and structure modification of various polymer materials (homopolymers, polymer blends, filled polymer composites) and makes it possible to produce fibers, films, pipes, shapes including those of large cross section and of different configurations, possessing high strength–stress characteristics.

In this article, much attention is given to the most known SSE versions—plunger extrusion and hydrostatic extrusion with the information on the influence of process controlling parameters on extrusion pressure, velocity of product exiting, value of extrudate swell, structure and properties of the processed material. There exists a region of controlling parameters where the process is stable; outside the region, the polymer flow is discontinuous, extrudate shape is imperfect and, finally, its failed.

Two new techniques of SSE are presented in brief, namely the equal channel angular extrusion and the twist extrusion which, in contrast to the conventional ones, are based on polymer simple shear, not drawing. These techniques are found to be promising for structure modification of polymers.