bluuebunny/crossref_metadata_2025_split huggingface dataset:
Membrane Technology
Authors: Baker Richard W. 
Published: October 2003

AbstractDuring the past 40 years a number of large industrial and medical applications of membrane technology have been developed. Several tens of millions square meters of membrane are produced each year, and the total industry sales have grown to $2–3 billion in sales per year. Most of this industry is focused on the use of membranes as selective barriers for various separation processes. In some processes (microfiltration, ultrafiltration, dialysis), permeating species cross the membrane through tiny pores that block large solutes but allow others to permeate freely. In other processes (reverse osmosis, gas separation, pervaporation), the membrane pores are so small, about 5–10 Å in diameter, that they are within the range of thermal motions of the polymer chains that form the membrane materials. Separation then occurs because of differences in the solubility and mobility of the permeating solutes in the membrane material.Early membranes were isotropic structures with uniform properties across the entire membrane, but now most membranes have an anisotropic structure consisting of a thin, dense selective layer, typically 0.1–2 μm thick, supported on a much more open, permeable layer (50–500 μm thick). This support layer provides sufficient mechanical strength to allow the membrane to be handled. By making the selective layer very thin, high permeation rates can be obtained. Even so industry processes often require very large membrane areas to perform the separation required; therefore, the technology to pack 10–100 m2of membrane in compact membrane modules of various designs has been developed. The techniques used to prepare membranes and membrane modules are described in this review.
Methacrylic Ester Polymers
Authors: Slone Robert V. 
Published: October 2003

AbstractThe commercially relevant and diverse chemistry of methacrylic ester polymers has encouraged their use in a remarkable variety of applications. Within this overview, particular attention is paid to the diversity of properties of methacrylic ester polymers and copolymers, the methods used to produce methacrylic ester polymers with specific properties, and the commercial applications of these materials.
Micromechanical Properties
Authors: Michler Goerg H. 
Published: October 2003

AbstractAn overview of successfully applicable techniques, particularly electron microscopy and scanning force microscopy, is given for the study of micromechanical mechanisms and properties in different polymers. Using modern developments in instrumentation, observation of realin situdeformation of structural details at the same place of a sample (eg, lamellae in polyethylenes) is possible.Crazing formation in amorphous polymers (polystyrene, styrene–acrylonitrile, polycarbonate) and tough‐brittle transitions depending on deformation temperature are described. General mechanisms of toughening and, in particular, effects of rubber‐toughening (eg, role of particle size, shape, and particle cavitation) in amorphous (high impact polystyrene, acrylonitrile–butadiene–styrene) and semicrystalline polymers (toughened polyamide, polypropylene, and polyethylene blends) are discussed. Individual deformation steps are summarized in a “three‐stage mechanism of toughening.” Processes of deformation of amorphous, interlamellar regions, twisting and breaking off of lamellae in semicrystalline polymers can be directly shown. Unusually large plastic deformations can be revealed in di‐, tri‐, and star‐block copolymers with a new “thin layer yielding mechanism.”Improved knowledge of micromechanical properties allows a deeper insight into the influence of morphology on mechanical properties and enables a defined modification of the morphology for improving the mechanical behavior of polymers for many practical applications, in a sense, “microstructural construction of polymers.”
Morphology
Authors: Bassett D. C. 
Published: October 2003

AbstractPolymer morphology contains a uniquely detailed record of the history of a polymeric material, notably its crystallization and deformation and has been the key to understanding the fundamental aspects of such behavior. Early understanding gained from solution‐grown lamellae has been brought up to date for melt‐crystallized polymers. Spherulitic structure is now well characterized and is attributed to adjacent dominant lamellae repetitively branching and then diverging. The divergence is due to repulsion by cilia pressure and/or the nonparallel packing of initially rough surfaces. The differing environments and lamellar orientations within spherulites lead to an inherent, spatially varying, spread of properties characteristic of semicrystalline polymers. The latest findings, that fold surfaces generally transform behind the growth front and that a memory of the initial transverse morphology is retained on drawing to very high extensions, give key insights, respectively, into banded growth as a means of relieving surface stress and into the details of deformation.
Nomenclature
Authors: Schultz J. L. , Wilks E. S. 
Published: October 2003

AbstractPolymer nomenclature is the naming of polymeric materials. The two principal approaches to nomenclature reflect the two methods used for graphical representation of polymers. Ideally, a structure‐based name should accompany a structure‐based representation of a polymer, while a source‐based name should accompany a source‐based representation. In practice, deviations from this ideal occur frequently, because the scientific community prefers structure‐based representations accompanied by source‐based names because they are easier to use. This article explains the principles of both structure‐based and source‐based nomenclature, and gives examples for a range of types, including regular linear single‐strand organic (random, statistical, block, graft, and modified), double‐strand organic (ladder and spiro), irregular single‐strand organic, inorganic, and coordination polymers. Stereochemistry in polymers is also covered. Nomenclature styles recommended by the International Union of Pure and Applied Chemistry and used by Chemical Abstracts Service are discussed.
Metal‐Containing Polymers
Authors: Abd‐El‐Aziz Alaa S. 
Published: October 2003

AbstractThe focus of this article is on the synthesis, properties, and applications of metal‐containing polymers. These polymers may be classified based on the types of metal–ligand bonding, and whether the metal is an integral part of the polymer backbone or pendent to the polymer backbone. The first class of polymers discussed are those with metals σ‐bonded to organic spacers in their backbones. Examples of metal–metal single and multiple bonds are also described. Metallocenes and coordination polymers are two classes of polymers where the metal is π‐coordinated to the organic ligands. The coordination of metals to porphyrins, phthalocyanines, Schiff base ligands, as well as to many other types of ligands are described. Another major class of polymers are those where the metal is pendent to the polymer backbone. These polymers include materials with metallic moieties π‐coordinated to unsaturated ligands in their backbones. Polymers with metallic moieties in their side chains are also described. A brief overview of star polymers and dendrimers is also included.
Phenolic Resins
Authors: Kopf Peter W. 
Published: October 2003

AbstractPhenolic resins are a family of polymers and oligomers composed of a wide range of structures based on the various reaction products of phenols with formaldehyde. Applications vary from commodity construction materials to high technology applications in electronics and aerospace. Phenolic resins are prepared using acidic or basic catalysts. Weak Lewis acids, such as zinc acetate, are used for specialty resins. Phenolic novolaks are thermoplastic resins prepared from acid catalysts and a molar excess of phenol. They have a molecular weight of 500–5000 and a glass‐transition temperatureTgof 45–70°C. Novolak resins are typically cured with 5–15% hexamethylenetetramine as the cross‐linking agent. Resole‐type phenolic resins are produced with a molar ratio of formaldehyde to phenol of 1.2:1 to 3.0:1 and alkaline catalysts such as NaOH, Ca(OH)2, and Ba(OH)2. A typical resin has an initial molecular weight of 150 to perhaps 1500. For systems of unsubstituted phenols, the final cross‐link density is 150–300 atomic mass units per cross‐link. In 2001, worldwide consumption of phenolic resins exceeded 4 × 106t; slightly less than half of the total volume was produced in the United States, where the largest volume application is in plywood adhesives and accounts for ca 49% of U.S. consumption. As a mature industry, U.S. production of phenolic resins has paralleled the growth in the GNP. Applications for phenolic resins include coatings, adhesives, carbonless copy paper, molding compounds, bonded and coated abrasives, friction materials, foundry resins, laminates, air and oil filters, wood bonding, fiber bonding, composites, spherical fillers, and fibers. Factors contributing to the health and safety concerns of phenolic resins are related primarily to the presence of unreacted phenol and formaldehyde. Unreacted phenol in a resin can range from >10% for liquid resoles used in impregnation processes to <1% for novolaks intended for use as epoxy hardeners. Free formaldehyde can be 2–4% in liquid adhesives.
Phosphorus‐Containing Polymers and Oligomers
Authors: Weil Edward D. 
Published: October 2003

AbstractVarious phosphorus polymers and oligomers, particularly phosphates and phosphonates, are commercially used as flame retardants. Some, such as phosphate oligomers with hydroxyl groups, are incorporated into polyurethanes, or into paper and textile finishes. Certain phosphonate or phosphinate structures are incorporated into thermoplastic polyesters, particularly textile fibers, for flame retardancy. Thermoset resins such as epoxy resins for circuit boards are rendered flame retardant by incorporation of phosphorus ester structures into the polymer structure. Flame‐retardant cotton finishes utilizing phosphonium reagents to produce cross‐linked phosphine oxide networks are commercially produced. Red phosphorus is a polymeric form of phosphorus and is used in Europe and the Far East as a flame‐retardant additive. An oligomeric ammonium polyphosphate is used as a component of intumescent systems, especially for coatings and fire barrier materials.Some oligomeric phosphites are used as antioxidant components. Oligomers with phosphonic and phosphinic groups are used commercially in scale inhibition. Vinylphosphonic acid polymers have found specialized uses in coating photolithographic plates. Phosphorylated acrylic monomers have been found useful for improving adhesion of coatings and dental repair materials. Ion‐exchange resins with phosphorus acid groups show promise for removal of water pollutants. Phosphorylated cellulose has a specialized medical use for binding calcium in the gastrointestinal tract. Phosphorylated starches have rheological applications in food products.
Polyamides, Aromatic
Authors: Gallini J. 
Published: October 2003

Abstract

This article describes the preparation and properties of aromatic polyamides and the fibers and films made from those polymers. A number of such polymers are identified, but the main focus is on the relatively few polymers that have achieved commercial status, namely, poly(
m
‐phenylene isophthalamide), poly(
p
‐phenylene terephthalamide), and copoly(
p
‐phenylene/3,4′‐diphenyl ether terephthalamide). The processes for manufacture of the corresponding monomers for these three polymers are described briefly. Both laboratory and commercial scale processes for the preparation of the polymers are presented and the processes for the commercial production of the fibers and films from these polymers are described. Properties of the polymers and the commercial fibers and films are tabulated. These products include trademarks such as Teijinconex, Nomex, Kevlar, Twaron, Technora, Aramica, and Mictron. The principal end uses are described. Estimates of current sales volumes are cited, along with price ranges for the products. Health and safety concerns are identified.
Polyamides, Fibers
Authors: Anton Anthony , Baird Bennett R. 
Published: October 2003

AbstractPolyamide fibers are melt spun from linear semicrystalline thermoplastic polymers having recurring amide groups made from diamines and dicarboxylic acids or lactams. Poly(hexamethyleneadipamide), designated as nylon‐6,6, and poly(caprolactam), nylon‐6, account for 98% of the 4 million metric tons of the worldwide annual production of nylon fiber. The attributes of nylon such as high strength, durability, abrasion resistance, resilience, moderate hydrophilicity, ease of dyeability, and low specific gravity have been recognized since its introduction in 1938. Both the inherent properties and those properties that can be engineered into the fiber manufacturing and ultimately into the fabric in downstream mill processing combined with reasonable market pricing account for the diverse end uses and market longevity of nylon. Nylon fiber is offered in the forms of continuous flat and textured filaments, staple, tow and flock for hosiery, apparel, home, flooring, industrial and transportation fabric applications. The physical appearance, functionality, and end‐use performance of nylon fibers can be modified by incorporating additives, eg, delusterants, colorants, antioxidants, or antistats in the polymer, by designing a spinneret hole configuration to impart a desired luster, surface effect or specific dtex‐per‐filament, by spinning bicomponent or biconstituent fibers, and by chemically or mechanically treating the surface of the fiber or fabric.
Polyanhydrides
Authors: Kumar Neeraj , Zhao Zhong , Domb Abraham J. 
Published: October 2003

Abstract

Polyanhydrides have gained a tremendous impetus in pharmaceutical applications especially for short‐term drug delivery. These polymers are hydrolytically unstable and can be easily manipulated for specific applications by modification of their polymeric backbone. The main advantages of these polymers are that they are biocompatible, easy to prepare, based on low cost, easily available starting materials, and degrade into nontoxic low molecular weight monomers. This article given a historical overview of polyanhydrides, and describes then synthesis, structure and properties, characterization, processing for pharmaceutical application, and their

in vivo

fate after implantation. Various pharmaceutical applications of polyanhydrides and their world market are also discussed.
Polyarylates
Authors: Shirahama Yutaka , Ohama Fumio 
Published: October 2003

Abstract
Polyarylate polymers are aromatic polyesters derived from aromatic dicarboxylic acids and diphenols. The polymers are heat‐resistant amorphous thermoplastics with excellent toughness, uv stability, flexural recovery, dimensional stability, and electrical properties. Polyarylates are transparent and range in color from light yellow to amber. These materials are used in automotive, safety, electrical and electronics, construction, and lighting applications.
Polycarbonates
Authors: Brunelle Daniel J. 
Published: October 2003

Abstract
Polycarbonates are a unique and useful class of engineering thermoplastics, known for their toughness, high heat properties, and optical clarity. Polycarbonates are manufactured by a number of companies, including GE Plastics (Lexan), Bayer (Makrolon), Dow Chemical (Caliber), Teijin Ltd. (Panlite), and Mitsubishi Gas Chemical (Iupilon), as well as many others. Most commercial polycarbonates are based on bisphenol A (2,2‐bis‐[4‐hydroxyphenyl]propane) and blends of that polycarbonate with other materials. Polycarbonates are prepared commercially by two chemical processes: Schotten–Baumann reaction of bisphenol A with phosgene in an interfacial, amine‐catalyzed condensation in a chlorinated solvent, or via a base‐catalyzed transesterification reaction of bisphenol A with diphenyl carbonate carried out in the melt. Each process has its own advantages and disadvantages. Global production is currently over 2 million tons annually. Research on polycarbonates continues to be carried out both in academics and in industry, with nearly 20,000 patents having appeared globally.
Cyclohexanedimethanol Polyesters
Authors: Turner S. Richard , Seymour Robert W. , Smith Thomas W. 
Published: October 2003

AbstractThermoplastic polyesters containing 1,4‐cyclohexanedimethanol (CHDM) posses a wide range of useful properties such as toughness, clarity, solvent resistance, and find broad applications in injection molding and extruded sheet products. The properties of these polyesters and copolyesters vary from the high melting crystalline poly(1,4‐cyclohexylenedimethylene terephthalate) (PCT) to the amorphous copolyesters based on combinations of ethylene glycol and CHDM in the backbone. The properties of these polyesters can also be dependent on the cis/trans ratio of the CHDM monomer. PCT can also be modified with diacids such as isophthalic acid to give commercially important tough amorphous polyesters with superior resistance to hydrolysis.
Polyelectrolytes
Authors: Hoagland David 
Published: October 2003

AbstractPolyelectrolytes are polymers that develop substantial charge when dissolved or swollen in a highly polar solvent medium such as water. The attendant electrostatic interactions — within a single polyelectrolyte, between polyelectrolytes, or with molecules/surfaces — produce physical properties much different than those for neutral polymers. Most polyelectrolyte solution and gel properties vary sharply with addition of simple electrolytes, which screen electrostatic interactions according to concentration. Scientists are just beginning to understand polyelectrolyte electrostatic interactions, which are known to play an important role in the natural world. Important concepts for polyelectrolytes are counterion condensation, electrostatic persistence length, electrostatic excluded volume, and Donnan equilibrium. Properties such as low angle scattered intensity, solution viscosity, osmotic pressure, polyelectrolyte and counterion diffusion coefficients, conductivity, adsorption, complexation, electric and magnetic birefringence, electrophoresis, titration, and gel swelling can only be understood by accounting properly for electrostatic interactions. These distinctive properties underlie applications in colloid stabilization, surface modification, rheology control, and controlled release.
Polyesters, Fibers
Authors: Reese Glen 
Published: October 2003

Abstract
In the half‐century since its introduction, polyester fiber has grown to dominate the global textile and technical markets. Its unique blend of performance, price, and flexibility has made it the preferred fiber over natural and other synthetic fibers in many large end uses. Variants of the basic PET polymer have been developed to provide specific performance traits for specialized needs, and the technology for making fibers has advanced considerably in areas such as consistency, performance, and low cost. The commoditization of the process technology has made PET fiber production an industry of choice for developing countries, where it can supply a downstream industry that is labor cost‐intensive, such as manufactured apparel. Fiber producers in developed countries depend more and more on industrial and technical markets that are less sensitive to labor costs, such as nonwoven fabrics. The global future of PET fibers appears bright because of the commanding advantages that have been established throughout the supporting infrastructure of raw materials supplies and manufacturing technologies.
Polyesters, Thermoplastic
Authors: East Anthony J. 
Published: October 2003

AbstractThis article describes the technology of poly(ethylene terephthalate) and poly(butylene terephthalate) polymers, two of the largest volume commercial thermoplastic polyesters. After a brief historical survey, the chemistry and synthesis of the monomers and their polymerization chemistry is separately discussed. Processes for achieving high molecular weight are discussed and the physical and chemical properties of the polymers described in detail. In the case of PET, particular attention is given to its use in the very rapidly growing area of blow‐molded bottles and various packaging outlets. Descriptions of polymer manufacture, bottle blowing, and its particular stringent technical requirements are given, together with brief descriptions of recycling processes. The injection molding of both polymers as well as the use of flame‐retardant polymer additives is outlined. Outlines of world markets for both materials and their commercial growth prospects are included.
Poly(3‐hydroxyalkanoates)
Authors: Ramsay Bruce A. , Ramsay Juliana A. 
Published: October 2003

AbstractPolyhydroxyalkanoates (PHAs) are polyesters, usually of 3‐hydroxycarboxylic acids, accumulated as inclusion bodies by bacteria. At least two classes of PHAs exist. Each is composed of many different homo‐ and copolymers. Most can be produced from renewable resources, are readily environmentally degradable, and are relatively resistant to abiotic hydrolysis. Polymers with reactive groups in their side chains can be synthesized to allow further chemical processing, leading to an even greater selection of polymeric materials. Thermomechanical properties vary from hard and brittle to elastomeric and tough. From the poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) copolymer alone, blow‐molded, injection‐molded, woven fiber, and coated paper products have been fabricated. Other properties of biologically produced PHAs such as optical purity, compatibility with human tissue, and piezoelectric properties make these materials of great commercial interest. They would certainly find wide application if it were not for their present high cost of production.
Polyimides
Authors: Bryant Robert G. 
Published: October 2003

AbstractPolyimides are a class of high performance polymers that contain an imide group, defined as ansp3nitrogen bonded to two adjacent carbonyls. This imide structure is most commonly found as part of a five‐ or six‐membered ring. Polyimides are noted for their mechanical properties, chemical resistance, and dielectric strength. They exist as thermoplastics and thermosets. Polyimides are used as hot melt adhesives, matrix resins for composites, dielectric films, photoimageable coatings, flex circuits, foams, wire insulation, thin‐walled tubing, molding resins, and high performance bushings and seals. Products that compete with polyimides for niche applications include aerospace epoxies (Dow, Ciba, and Shell), cyanate resins (Dow), polysulfones (Solvay), filled polycarbonates and polyesters (Dow, Amoco, and GE), polybenzimidazoles (Hoechst‐Celanese), and some highTgfilled phenolics. Although polyimides command a premium price, their versatility, reliability, and demonstrated performance make them suitable for use in high performance applications where failure and replacement costs are high.
Polyketones
Authors: Drent E. , Mul W. P. , Smaardijk A. A. 
Published: October 2003

AbstractAliphatic polyketones are a new family of polymers obtained by the palladium(II)‐catalyzed, perfectly alternating copolymerization of CO and olefins. Various aspects of polyketone catalysis, the polymerization process, the types and properties of polyketones, and their applications are reviewed, with special emphasis on commercial grades of CO/ethene/propene‐based terpolymer, a new semicrystalline engineering thermoplastic.