bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon Fibers
Authors: Newell James A. 
Published: July 2004

Abstract

Carbon fibers provide exceptional properties when used as reinforcing materials in
composite materials
. This article describes the production, processing, and properties of carbon fibers made from a variety of precursor materials. Most commercial carbon fibers are made from polyacrylonitrile (PAN), which must be converted to a thermally stable form that will not melt. The resultant carbon fibers have a fibrillar microtexture and exhibit exceptional tensile strength. Carbon fibers made from stabilized mesophase pitch, either petroleum‐based or synthetic, tend to possess lower strengths, but can exhibit vastly superior lattice‐dependent properties including thermal conductivity and Young's modulus. By controlling the flow of the liquid crystalline mesophase domains, the orientation and properties of the fiber can be improved substantially. High performance polymers such as Kevlar and poly
p
‐phenylene benzobisoxazole (PBO) can be converted directly to carbon fiber without the stabilization step, but have lower mechanical properties. Activated rayon‐based carbon fibers provide an economically attractive means of adsorbing many organic contaminants. Vapor‐grown carbon fibers (VGCFs) are produced by the decomposition of methane or benzene over a catalyst. Submicron VGCFs have commercial applications in batteries, while large VGCFs provide potentially inexpensive filler material in composites.
Characterization of Polymers
Authors: Pethrick Richard A. 
Published: July 2004

AbstractIn order to effectively use polymeric materials, it is important to understand what factors influence their physical and chemical properties. This article attempts to develop a framework for the systematic discussion of the characteristics of polymeric materials in terms of the methods used in their synthesis, the dominant nature of the organization or lack of it in the solids state, and their process ability. Many properties of a polymer are influenced by the length or the polymer chain or its size, and techniques which allow quantification of these properties are very important in defining the nature of a polymer. The final physical properties of a polymer can be influenced by the nature of the structure developed on formation of a solid, and relating physical properties to morphology is often required in order to understand the subtle effects which can be observed and to make polymeric materials commercially interesting for a wide range of applications.
Dynamic Mechanical Analysis
Authors: Menard Kevin P. 
Published: July 2004

AbstractDynamic mechanical analysis (DMA) measures the damping of an oscillatory signal in a material. The technique allows the detection of very weak transitions as well as fast determinations of modulus as a function of temperature and frequency, damping, viscosity, and compliance. It is commonly used to study polymer melts as well as solid polymers. It has the advantage of allowing testing on a wide variety of materials, and both liquids and solids can be handled in the same instrument, making it extremely useful for the study of curing systems.
Fractionation
Authors: Soares Joao B. P. 
Published: July 2004

Abstract
Polymer fractionation techniques attempt to fractionate polymers according to specific characteristics of their microstructures as defined by their distributions of molecular weight, chemical composition, comonomer sequence length, tacticity, and long‐chain branching. Because of the heterogeneous nature of polymers, fractionation techniques are essential for understanding structure‐property relationships, polymerization mechanisms and kinetics, and polymer reaction engineering.
In this entry, theoretical models to describe the microstructure of polymers are initially reviewed and used as a basis to understand the several polymer fractionation techniques described in the subsequent sections. Batch fractionation methods are covered next, including temperature variation and solvent/nonsolvent fractionation procedures. The recent technique of crystallization analysis fractionation (Crystaf), together with temperature rising elution fractionation (TREF), are reviewed as methods for fractionation by crystallizability. The well‐established technique for molecular weight fractionation by size‐exclusion chromatography (SEC) is covered next, followed by a section on the versatile field flow fractionation (FFF). Large‐scale fractionation of polymers is covered in the section for continuous polymer fractionation (CPF). Mass spectrometry, particularly matrix‐assisted laser desorption ionization coupled with time‐of‐flight analyzers (MALDI‐TOF) is the subject of the next section. Finally, a section in interaction chromatography and some other less general polymer fractionation techniques is followed by the concluding section on cross‐fractionation techniques.
Polypeptide Synthesis, Solid‐Phase Method
Authors: Barany George , Kneib‐Cordonier Nancy , Mullen Daniel G. 
Published: July 2004

AbstractSolid‐phase peptide synthesis (SPPS) has continued to evolve since originally conceived by R.B. Merrifield in 1959. This article is a general introduction into the current state of the art of SPPS. The review covers synthesis strategies, including protecting group combinations, coupling chemistry, monitoring, solid supports, cleavage, and purification. The most troublesome side reactions are also covered. Finally, the prognosis for future developments in SPPS is discussed.
Polypeptide Synthesis, Ring‐Opening Polymerization of α‐Amino AcidN‐Carboxyanhydrides
Authors: Klok Harm‐Anton 
Published: July 2004

AbstractThe ring‐opening polymerization of α‐amino acidN‐carboxyanhydrides (NCAs) represents the most convenient pathway for the large‐scale synthesis of polypeptides. Traditional initiators for the NCA ring‐opening polymerization include a variety of nucleophiles and bases. NCA polymerizations initiated by such initiators, however, proceed along multiple concurrent pathways, which hampers precise control over molecular weight, molecular weight distribution, composition, and architecture of the resulting polypeptides. A second parameter, which is of critical importance for the polymerization of NCAs, is monomer purity. This contribution provides an overview of the current methods for the synthesis and polymerization of NCAs. In addition to the traditional methods for NCA synthesis and polymerization, several recent developments are discussed that allow controlled/“living” polymerization of NCAs and facilitate the synthesis of structurally well‐defined polypeptide architectures.
Rubber Compounding
Authors: Rodgers Brendan , Waddell Walter H. , Klingensmith William 
Published: July 2004

AbstractRubber compounding is the complex, multidisiplinary science of selecting and blending the optimum combination of elastomer and other ingredients that meet the performance, processing, environmental, and cost requirements for rubber goods made and used in commerce. Chemical and physical properties of the wide variety of elastomers and ingredients available in making rubber goods are provided. Vulcanization, oils, plasticizers, general compounding, curing, fillers, latex, and testing are discussed.
Silk
Authors: Kaplan David L. 
Published: July 2004

AbstractSilks are naturally spun fibrous proteins most often associated with silkworms and spiders. Silk fibers are unusual in combining strength, toughness, and resistance to mechanical compression. The proteins are characterized by a β‐sheet secondary structure for the highly crystalline regions, as well as regions of lower crystallinity. Silkworm cocoon fibers have been used in textiles for thousands of years. Silk production by spiders has not been domesticated to date. Water‐soluble silk proteins are synthesized and stored in glands until spun into fibers, via micellar and gel states, at which point they become insoluble in water upon spinning. The silk spinning process is regulated by the organism and involves the extrusion of the silk gel in a liquid crystalline state through spinnerettes. Silk fibers are mechanically stable to approximately 200°C. Membranes, hydrogels, fibers, and foams have been formed from reconstituted silks that provide useful means to explore structure development, to entrap enzymes, and for use as biomaterial scaffolds such as for tissue engineering. Worldwide production of silkworm silk for textiles is expected to increase, and future applications will depend on biotechnological approaches to generate suitable levels of specifically tailored silk compositions.
Sutures
Authors: Chu C. C. 
Published: July 2004

AbstractAmong wound closure biomaterials, sutures have the longest history, have received the most attention, and are the most widely used. A suture is a strand of material, either natural or synthetic, used to ligate blood vessels and to approximate tissue together. In this article, all aspects of suture‐based wound closure biomaterials, their classification, and chemical, physical, mechanical, biological, and biodegradation properties are concisely covered. Catgut and silk dominated the suture market until 1930. The introduction of steel wire and synthetic nonabsorbable fibers such as nylon, polyester, and polypropylene during and after World War II greatly expanded the chemical composition of suture materials. The introduction of absorbable suture materials in the 1970s opened a new milestone for suture materials. The most important advantage of synthetic absorbable sutures is their reproducible and predictable degradability inside a biological environment.
Transport Properties
Authors: Koros William J. , Madden William C. 
Published: July 2004

Abstract
This article covers the transport properties of gases, low activity vapors, and intermediate‐sized penetrants through rubbery, semicrystalline, and glassy polymers. The article emphasizes polymer transport properties under conditions of low to intermediate penetrant concentration where extraordinary differences can exist between the diffusivities of penetrants having relatively small differences in molecular size or shape. Nonideal transport effects, such as plasticization, clustering, and non‐Fickian transport, are covered. Particular attention is given to the nonequilibrium nature of glassy polymers and the resulting effects on penetrant transport. The recent development of positron annihilation lifetime spectroscopy (PALS) and molecular modeling of diffusion are described. Transport through porous polymers and reptation of macromolecules within a macromolecular matrix are not covered in this article.
Vinyl Acetate Polymers
Authors: Cordeiro Cajetan F. , Petrocelli Francis P. 
Published: July 2004

AbstractThis article provides information related to the chemistry, manufacture, and use of poly(vinyl acetate). Summary information is provided on vinyl acetate as the primary ingredient in the manufacture of the polymer. This information focuses on the chemical and physical properties of the material and the handling and safety aspects pertinent to its use in a polymerization system. The key material properties of poly(vinyl acetate) homopolymer and copolymers are described. The influences of key components of the polymerization recipe are discussed, such as the effect of the stabilizers, comonomers, and chain‐transfer agents on the reaction and product. Polymerization process aspects are covered with a focus on emulsion polymerization. The mechanisms involved in the vinyl acetate polymerization reaction are discussed. An overview is provided of the applications of the homopolymer and copolymers in adhesives, paint, paper, and other areas. General information is provided in these areas with references which can be used to obtain more specific information.
Degradable Polymers and Plastics in Landfill Sites
Authors: Swift Graham , Wiles David M. 
Published: July 2004

AbstractThrough the ages, landfill sites have been the repositories of human garbage. They were once prized sites for excavation to yield information of past cultures and civilizations. However, with the advent of the polymer and plastics age, what had once been an acceptable level of landfill waste of pottery, metals, and yard and agricultural debris became significantly larger in volume with the disposal of low density plastic waste from packaging and polymers from the ubiquitous disposable diapers, for example. This serious situation, of course, has had a very adverse effect on the number and capacity of landfill sites available for the disposal of all grades of trash. The very apparent limitation of available sites precipitated the waste‐management era, where alternative approaches were considered and developed to at least limit the problem. Some of these alternatives include recycling, incineration, and biodegradation under controlled environmental conditions such as composting. Not unexpectedly, the development of suitable polymers and plastics and the implementation of these alternatives is a slow process. Consequently, there are still huge amounts of plastic and polymer residues that are entering landfill sites every year. This article attempts to overview the issue and to summarize the limited evidence that we have on waste polymers and plastics as to their ultimate fate—recalcitrance, degradation, or biodegradation.
Scratch Behavior of Polymers
Authors: Wong Janet S. S. , Sue Hung‐Jue 
Published: July 2004

AbstractScratch and wear is a long existing deteriorating phenomenon occurring when two moving surfaces are in intimate contact. This problem in polymers has been emphasized because of the increasing popularity of polymers as the materials of choice in various applications. It is thus important for us to understand this phenomenon in order to engineer polymers with good scratch and wear resistance. This article focuses on the fundamental process that leads to abrasion and wear, ie, scratch behavior of polymers. The objective of this article is to highlight the importance of understanding scratch behavior of polymers by giving readers an up‐to‐date knowledge in this field of research. The theoretical framework concerning interfacial contacts and the experimental aspects in terms of methodology and quantitative measures is introduced. The effects of various material and testing parameters on the scratch behavior of polymers are summarized. Directions for future research are also suggested.
Melamine–Formaldehyde Resins
Authors: Binder Wolfgang H. , Dunky Manfred 
Published: July 2004

AbstractMelamine‐based resins [MF, MUF, MUPF, PM(U)F] used as wood adhesives represent one of the largest groups of aminoplastic resins. They are made by the reaction of formaldehyde with melamine using urea, phenol, or other components as comonomers. The hardened resins show duroplastic hardening behavior; they are three‐dimensionally cross‐linked and hence insoluble, nonmeltable networks. Analytical methods to determine the chemical identity of the complex mixtures (ie, NMR spectroscopy, IR spectroscopy, HPLC, as well as mass spectrometry) are described in this article. Melamine‐based resins show higher hydrolysis resistance compared to UF resins. The field of application comprises the production of wood‐based panels such as particleboards, MDF, OSB, plywood, blockboards, and others especially for use under humid conditions. The molar ratio between formaldehyde/reactive amino groups [F/(NH2)2] distinctly determines reactivity, the degree of cross‐linking, and hence the bonding strength. Cocondensation between melamine, formaldehyde, and other components (such as urea and phenol) is possible, furnishing cocondensates with improved properties and reduced price.
Telechelic Polymers
Authors: Yagci Yusuf , Nuyken Oskar , Graubner Vera‐Maria 
Published: July 2004

AbstractIn this article common synthetic routes toward telechelics, which are polymers with well‐defined functional end groups, are described. Telechelic polymers are available via radical, cationic, and anionic polymerization including reversible addition–fragmentation chain transfer polymerization, atom transfer radical polymerization, and nitroxide mediated polymerization. Furthermore, metathesis has become a valuable tool for the preparation of telechelics. Last but not least selected examples are presented in which step‐growth polymerization has been successfully applied for the synthesis of such well‐defined macromolecules. In specific cases chain scission can also be a useful route.
Scanning Force Microscopy
Authors: Schönherr Holger 
Published: July 2004

AbstractScanning force microscopy (SFM) belongs to a class of real‐space microscopic techniques, which combine high spatial resolution, 3‐D imaging capabilities, and contrast mechanisms based on specific materials contrast. In particular, in the field ofpolymer science and technology, SFM quickly developed into an indispensable characterization technique and has found widespread use. In this article the application of SFM to polymers is discussed based on a selection of topics covering the whole breadth from topography imaging to mapping of surface properties and studies of dynamic processes in real time. The basic concepts and modes of SFM, as well as some rudimentary theory, are introduced as a self‐supporting basis for the following sections. The visualization of the morphology and ordering of polymers at various hierarchical levels is reviewed starting from the visualization of single macromolecules, chain packing, and surface crystal structures. The imaging of lamellar crystals, hedrites, and spherulites by SFM approaches is discussed, followed by studies of the effects of deformation and processing, as well as studies on the morphology of latex particles and fibers. The mapping of surface properties and composition in the heterogeneous and surface‐modified polymer systems via the spatially resolved measurement of adhesion and friction forces, as well as surface mechanical properties, are covered. The final section is focused onin situstudies of structure development and dynamic processes, including polymer crystallization, followed in real time by SFM.
Nonwoven Fabrics, Staple Fibers
Authors: Chapman Roger 
Published: July 2004

Abstract
This article provides an overview of the production methods, properties, and uses of nonwoven fabrics. The discussion includes a brief introduction, short history, and compilation of definitions of a nonwoven fabric. Staple fiber processes, including fiber selection, web formation, web layering, web consolidation, and finishing, are described. Descriptions and illustrations of the manufacturing sequences follow. Production trends and product applications are discussed.
Ultrasound‐Induced Radical Polymerization
Authors: Kuijpers Martijn W. A. , Kemmere Maartje F. , Keurentjes Jos T. F. 
Published: July 2004

AbstractSonochemistry comprises all chemical effects that are induced by ultrasound. Most of these effects are caused by cavitations, ie, the collapse of microscopic bubbles in a liquid. The chemical effects of ultrasound include the formation of radicals and the enhancement of reaction rates at ambient temperatures. For the development of sustainable polymer processes, ultrasound is an interesting technology, as it allows for polymerizations without the use of initiator. The radicals are generatedin situby cavitation events, which enable a clean and intrinsically safe polymerization reaction. As a result of the high strain rates outside the bubble, cavitation can also induce chain scission, which provides an additional means to control the molecular weight of the produced polymer. This article discusses the possibilities, mechanisms, and challenges of several types of ultrasound‐induced radical polymerizations.
Latex Technology
Authors: Grady Michael C. 
Published: July 2004

AbstractLatices are colloidal dispersions of discrete polymer particles, usually in an aqueous medium. Technology used to make and use latex involves many aspects of colloidal and polymer chemistry. This article reviews the fundamentals of emulsion polymerization, the techniques used to make most synthetic latices, general properties of latices, as well as colloidal and polymer compounding ingredients to convert latices into useful products, and discusses the wide variety of applications in which latices are used.
Electron Spin Resonance
Authors: Schlick Shulamith , Jeschke Gunnar 
Published: July 2004

AbstractThis article begins with a description of the fundamentals of electron spin resonance (ESR) spectroscopy, with emphasis on the experimentally available parameters relevant for elucidation of the polymer structure, dynamics, transport, and stability. Advanced ESR methods, including high field and time‐domain ESR, and double resonance methods are then outlined. The part that describes the ESR methods concludes with an outline of the transition from ESR spectroscopy to ESR imaging.Specific, and important, applications of ESR spectroscopy to polymeric systems follow: the use of CW ESR of nitroxide spin probes to describe the local polarity and dynamics in ion‐containing polymers; pulsed ESR methods for the characterization of the distribution and structural parameters of ion clusters in telechelic block‐copolymer based ionomers; and spatially resolved degradation in heterophasic polymers by 1‐D and 2‐D spectral‐spatial ESR imaging.The article concludes with an evaluation of the strengths of ESR methods, and views on further applications of this approach and on areas that require further development.
Intelligent Polymer Systems
Authors: Wallace G. G. , Innis P. C. , Moulton S. E. 
Published: July 2004

AbstractInherently conducting polymers (ICPs) are a unique class of materials that have the capability to not only conduct electricity but also undergo redox changes in response to an environmental stimulus. No other class of material is capable of undergoing such a broad range of transductions and as a result ICPs have been investigated for applications in an amazing array of areas. This review highlights the application of the ICP in areas such as sensing technologies, polymer actuators, molecular electronics, electrochromics, and energy conversion and storage. The facile nature of the ICP, in combination with novel polymer processing strategies, lends itself to the development of unique solutions in a diverse array of areas. The incorporation of the ICP into these technologies will ultimately lead to development of intelligent polymer systems, partly because of the amazing redox capabilities of these polymers.
Ethylene Oxide Polymers
Authors: Back Darlene M. , Schmitt Robert L. 
Published: July 2004

AbstractEthylene oxide polymers are high molecular weight (>100,000) water‐soluble thermoplastic polymers. This article reviews the effect of shear, pH, salt, and temperature on the physical and chemical properties of poly(ethylene oxide) solutions and melts. Industrial uses of the unique properties of poly(ethylene oxide) in fields such as flocculation, pharmaceutical excipients, adhesives, coatings, and personal care are summarized.