bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorus‐Containing Polymers and Oligomers
Authors: Weil Edward D.
Published: October 2003

Various 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

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

Polyamide 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

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

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

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

Thermoplastic 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

Polyelectrolytes 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

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

This 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

Polyhydroxyalkanoates (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

Polyimides 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

Aliphatic 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.
Polymeric Drugs
Authors: Dhal Pradeep K. , Holmes‐Farley S. Randall , Mandeville W. Harry , Neenan Thomas X.
Published: October 2003

This article summarizes opportunities and challenges associated with discovery and development of polymeric drugs. Polymeric drugs possess unique pharmaceutical properties that are fundamentally different from low molecular weight drugs. The basic principles associated with polymeric drugs are examined and intrinsically active polymers as pharmaceutical agents are distinguished from polymers that act as carriers for drug delivery. In some applications, polymeric drugs involve selective recognition, binding, and removal of target disease‐causing substances. The design, discovery, and clinical development of polymeric drugs that act as sequestrants for low molecular weight cations and anions (eg, potassium, phosphate, and bile salts), which are responsible for different disease states, are surveyed. Examples of polymeric drugs that are on the market are provided. The use of the principle of “polyvalent interaction” to develop polymeric drugs is described. After a brief discussion of the theoretical framework for polyvalency, this section surveys the design of polymeric agents for the complexation of pathogens and pathogen‐derived substances (ie, toxins, viruses, and bacteria). Approaches for designing polymer structures to achieve highly active materials are described.
Polynucleotides
Authors: Kushon Stuart A. , Armitage Bruce A.
Published: October 2003

This article describes the structural and functional properties of polynucleotides, beginning with a description of the hierarchical levels of structure exhibited by the natural polynucleotides, DNA and RNA. This is followed by a description of modern methods for characterizing polynucleotides and their complexes, including electrophoresis, calorimetry, and spectroscopy. Enzymatic and chemical methods for synthesizing oligo‐ and polynucleotides are then reviewed. This leads to a description of synthetic polynucleotide analogues, which find widespread use in biotechnology and clinical diagnostics. Molecular mechanisms for sequence‐specific recognition of DNA and RNA are described, followed by a survey of methods for preparation and properties of functional polynucleotides, broadly defined as those sequences which fold into a well‐defined three‐dimensional structure that exhibits a function, such as selective binding to a ligand or catalysis of a chemical reaction. The article concludes with a summary of recent work in which polynucleotides are used as construction materials for the assembly of nanomaterials.
Polysilanes
Authors: Oka Kunio
Published: October 2003

Polysilanes have σ‐conjugated backbones and organic side groups. The energy state of polysilane is influenced by molecular weight, conformation of the backbone, side groups, and branching points. Sigma‐conjugated polysilanes show strong absorption and efficient emission in the UV region. These properties are sensitive to external stimuli and show interesting thermochromism, piezochromism, electrochromism, and solvatochromism. Undoped polysilanes are insulators but they become conductive on doping. Polysilanes are also photoconductors showing high hole drift mobility. Polysilanes are thus studied as resist materials for photo or X‐ray lithography and as emissive or hole transport materials of LEDs. The siloxane part after photolysis is used for color filter production, recording material, printing material, and production of microlens. Polysilanes are synthesized by five methods: Wurtz coupling, dehydro‐coupling, ring‐opening polymerization, anionic polymerization of masked disilene, and redistribution polymerization of alkoxylated disilanes. Functional polysilanes are prepared from SiH, SiCl, and chloromethylphenyl groups. Block copolymers with carbon blocks are prepared by photolysis of polysilanes in carbon monomers, reaction of SiCl end with living carbon polymers, atom‐transfer polymerization with carbon monomers, and polymerization of carbon monomers with living polymer from masked disilene.
Polysulfides
Authors: Vietti David
Published: October 2003

Polysulfide elastomers were the first synthetic rubbers produced in the United States. They are made from simple, low cost starting materials. Polysulfides are available as viscous liquids which are commonly cured through oxidative coupling of the terminal thiol group (eg, with MnO
2
). But, this versatile end group allows these resins to be cured with other reagents such as diisocyanates, diacrylates, or epoxides. Polysulfide elastomers have unusually good resistance to solvents and to the environment. This and their good low temperature properties have made them particularly useful in the sealant applications. They are the standard sealant for virtually all aircraft integral fuel tanks and bodies. Polysulfides are the worldwide market leader in insulating glass sealants and have been used since the 1950s as construction sealants. Also, polysulfides are commonly used as flexibilizers and reactive diluents in epoxy formulations. Furthermore, the unique properties of polysulfides make them useful in a variety of specialty rubber applications.
Polysulfones
Authors: El‐Hibri M. Jamal , Weinberg Shari A.
Published: October 2003

Aromatic polysulfones are a family of polymers produced from the condensation polymerization of 4,4′‐dichlorodiphenylsulfone with one or more dihydric phenols. The three must commercially important polysulfones are bisphenol A based polysulfone (PSF), 4,4′‐dihydroxydiphenylsulfone‐based polyethersulfone (PES), and 4,4′‐dihydroxydiphenyl‐based polyphenylsulfone (PPSF). Polymers in this family are completely amorphous, exhibit high glass‐transition temperatures, and offer high strength and stiffness properties even at high temperatures, making them useful for demanding engineering applications. The polymers also possess good ductility and toughness and are transparent in their natural state by virtue of their fully amorphous nature. Additional key attributes include resistance to hydrolysis by hot water/steam and excellent resistance to acids and bases. The polysulfones are fully thermoplastic, allowing fabrication by most standard methods such as injection molding, extrusion, and thermoforming. They also enjoy a broad range of high temperature engineering uses. Some typical areas and industries where these polymers are used as materials of construction include hot food and beverage service, sterilizable medical components, hot water plumbing components, electrical/electronics, and a host of transportation uses in the automotive, rail, and aerospace industries.
Pressure‐Sensitive Adhesives
Authors: Cantor Adam S. , Menon Vinod P.
Published: October 2003

A review of pressure‐sensitive adhesives (PSAs) and PSA tapes is presented. Typical constructions of PSA tapes are discussed along with a short section on the release surfaces used in conjunction with most PSAs. A discussion of the physical properties governing PSA performance is provided with emphasis on the effect of the viscoelastic nature of PSAs on adhesion. The most common types of tapes—industrial, consumer and office, medical, and labels—are described along with reference to other specialty constructions. Test methods, including peel, tack, shear, and rheology, are described for PSA tapes. Sections describing the most common materials used as PSAs—block copolymers, natural rubber, and acrylics—are included along with short descriptions of silicones, polyisobutylene, and polyolefins. A short section on general manufacturing methods of PSAs and PSA tapes is also included.
Protein Folding
Authors: Gazit Ehud
Published: October 2003

The process of protein folding is one of the most significant mechanisms in biology. In spite of its great importance, this process is not fully understood and a final folded structure of a protein cannot be predicted from its amino acid sequence. In this article the experimental and theoretical advances in the study of protein folding are discussed. A conceptual milestone in the understanding of protein folding is the “thermodynamic theory,” establisted by Christian A. Anfinsen in the 1950s and early 1960s. The thermodynamic hypothesis suggested that a particular three‐dimensional structure of a protein occurs because this certain molecular arrangement is the most stable thermodynamically. Another key insight regarding the mechanism of protein folding is the “Levinthal's paradox.” This paradox indicates that it is not possible for a folding protein to sample the entire conformational space during the process, and a certain folding pathway should exist. This was further developed into an energy landscape view of the folding process and into computational attempts to understand and predict the folding process. A major medical concern is related to cases of incorrect protein folding or “misfolding.” Recent studies pave new ways into true understanding of the process and ways of its control.
Radical Polymerization
Authors: Vana Philipp , Barner‐Kowollik Christopher , Davis Thomas P. , Matyjaszewski Krzysztof
Published: October 2003

The present article summarizes the fundamental principles and recent advances in free radical polymerization systems. Each individual reaction step in the polymerization process—initiation, propagation, transfer, and termination—is discussed in detail with regard to the underlying first principles and to the latest rate coefficient data. Novel methodologies, including living free radical polymerization, are also introduced within this context. In addition, the article gives an up‐to‐date overview of current state‐of‐the‐art experimental techniques for obtaining reliable kinetic and mechanistic information, embedded in an extensive coverage of the rates of radical polymerization, thermodynamics, and the chain‐length distribution. Such techniques range from now quasi‐classic experiments, such as pulsed laser polymerization, size exclusion chromatography, and the chain‐length distribution method for transfer constant determination, to cutting edge methodologies, such as the use of living free radical processes for chain‐length‐dependent rate coefficient determination. The fundamental differential equations governing free‐radical polymerization and the chemistry involved are both extensively covered along with ample tabular material, giving the practicing polymer chemist up‐to‐date and easily accessible data material backed up by over 500 references.
Recycling, Plastics
Authors: Khait K.
Published: October 2003

Waste generation including plastics continues to increase, aided by the strong economic climate in the 1990s. In the United States, plastics contribute about 10 wt% of the total 230 million tons of waste generated. Most waste comes from municipal solid waste; other sources include autos, appliances, electrical and electronic components, and demolition and construction activities. Although millions of tons are landfilled annually, that is no longer considered a cheap or acceptable form of disposal.

Plastic recycling issues are complex. Important aspects include the environmental impact of growing natural resource consumption, the need to revise collection and reprocessing infrastructures, the relatively new “eco‐design” approach to products, and life cycle analysis of “cradle‐to‐grave” use. This article reviews the state of worldwide plastics recycling, the challenges facing this industry in the new millennium, and emerging technologies for addressing these issues.
Reinforcement
Authors: Wagner H. D.
Published: October 2003

Most materials achieve their strongest forms when they are in a fibrous shape. They also often appear to be anisotropic. The present article provides some details for the inherent source of fiber strength and stiffness, and reviews the basic principles of fiber reinforcement. Key parameters, such as interfacial adhesion, are succinctly discussed. An overview of the morphology, physical properties, and preparation technology of various reinforcing fibers is presented. The potential of biological fibers, and nanoscale fibers such as carbon nanotubes, as reinforcement in future applications is briefly discussed.
Rigid‐Rod Polymers
Authors: Jiang Hao , Eby Ronald K. , Adams W. Wade
Published: October 2003

The synthesis, structure, properties, and applications of rigid‐rod polymers are described. PBZT and PBZO are selected as the models to be discussed in detail with respect to their fiber, film, and molecular‐composite processing, liquid‐crystal solution behavior, and computer simulations. Emphasis is placed on their ultimate tensile, thermal, chemical, electrical, and optical properties, and how to improve their compressive properties. The current and future usages of rigid‐rod polymers in various scientific, technical, and engineering areas also have been introduced. Many new rigid‐rod polymer materials, such as PPP, PPE, PPV, PTh, and other organometallic polymer systems are included.
Shape‐Memory Polymers
Authors: Lendlein Andreas , Kelch Steffen
Published: October 2003

Shape‐memory polymers are stimuli‐responsive materials. Upon exposure to an external stimulus, they have the capability of changing their shape. A change in shape initiated by a change in temperature is called thermally induced shape‐memory effect. The shape‐memory effect results from the polymer's structure, that is, its morphology in combination with a certain processing and programming technology.

The polymer is processed into its permanent shape by conventional methods. Afterwards, it is deformed and the desired temporary shape is fixed. The latter process is called programming. Heating the programmed polymer above a temperature higher than the transition temperature
T
trans
results in activating the shape‐memory effect. As a consequence, the recovery of the memorized, permanent shape can be observed. The described effect is called a “one‐way” shape‐memory effect.

The shape‐memory effect can be quantified by cyclic thermomechanical investigations. Important quantities describing the shape‐memory properties of the material for a certain strain ɛ
m
are the strain recovery rate
R
r
and the strain fixity rate
R
f
. The strain recovery rate
R
r
quantifies the ability of the material to memorize its permanent shape. The strain fixity rate
R
f
describes the ability of the material to fix the mechanical deformation ɛ
m
which has been applied during the programming process.
Silicones
Authors: Butts Matthew , Cella James , Wood Christina Darkangelo , Gillette Gregory , Kerboua Rachid , Leman John , Lewis Larry , Rajaraman Suresh , Rubinsztajn Slawomir , Schattenmann Florian , Stein Judith , Wengrovius Jeffrey , Wicht Denyce
Published: October 2003

Silicones are a class of materials with unique properties that make them useful in a variety of applications of commercial interest and support a thriving global industry. This article updates a comprehensive survey of the chemistry and technology of silicones last published in Kirk‐Othmer Encyclopedia of Chemical Technology in 1997. The update contains more than 235 references not cited in the previous version and includes literature published through 2001. A new section dealing with fiber finishing applications has been included in the current version. The review provides an excellent primary reference for this interesting area of chemistry and technology.
Single‐Site Catalysts
Authors: Leino Reko
Published: October 2003

The recent rapid development of organometallic single‐site catalysts (SSCs) has revolutionized polymer synthesis and polyolefin production technologies. These well‐defined catalyst systems generally consist of a transition metal atom, such as titanium, zirconium, iron, nickel, or palladium, complexed with an organic ligand set and an initiating group(s). Activation with methylaluminoxane or other weakly coordinating anions generates the cationic active species responsible for olefin coordination and polymer chain growth. Representative examples of SSCs include the bis(cyclopentadienyl)‐type Group 4 metallocenes as well as the diimine complexes of nickel and palladium. By variation of the organic ligand and thus the steric and electronic environment of the metal center, these catalysts can be tailored to control the olefin polymerization reaction in an unprecedented fashion. Almost any vinyl monomer, irrespective of molecular weight or steric hindrance, can be polymerized by choosing the proper catalyst. Virtually all feasible poly(α‐)olefin microstructures ranging from atactic to isotactic, hemiisotactic, syndiotactic, and stereoblock polymers can be produced by rational modification of the catalyst structure. Functional monomers are readily copolymerized with the less oxophilic late transition metal catalysts. Entirely new materials, not accessible with traditional Ziegler–Natta catalysts, have emerged, including high melting syndiotactic polystyrene and cycloaliphatic polymers. This article provides a broad overview of SSCs and their application in olefin polymerization. Evolution and classification of SSCs, catalyst generation, polymerization of ethylene, propylene, cycloolefins, dienes, styrene, as well as as functional olefins, and the application of SSCs in enantioselective polymerization are covered. Finally, heterogenization of SSCs for use in industrial processes is briefly discussed.
Statistical Thermodynamics
Authors: Oono Yoshitsugu
Published: October 2003

The objective and mode of thinking of statistical thermodynamics are explained with key references. The problems of statistical thermodynamics fall into two categories: studies of universal structures and studies of materials constants. The modern statistical thermodynamics emphasizes the former category. Consequently, recognizing a universality class described by a well‐defined phenomenological framework and constructing a minimal model to elucidate it statistically are the key problems. From this modern point of view equilibrium and nonequilibrium statistical thermodynamics are outlined, with applications to polymer solutions.
Styrene Polymers
Authors: Priddy Duane
Published: October 2003

This article covers all aspects of styrene‐containing plastics and their copolymers, including properties, manufacturing processes, morphology, polymerization chemistry, environmental impact, rubber toughening, morphology, transparency, nanocomposites, and degradation. Special emphasis is given to new developments such as living free‐radical polymerization, transparent impact polystyrene, and polystyrene/inorganic nanocomposite materials.
Superabsorbent Polymers
Authors: Buchholz Fredric L.
Published: October 2003

Superabsorbent polymers are very high molecular mass, cross‐linked polyelectrolytes that can absorb more than 10 times their mass of water or aqueous solutions. The commercially available superabsorbent polymers are alkali matal salts of poly(acrylic acid) cross‐linked with multifunctional monomers. The polymers are usually made by means of free‐radical‐initiated polymerization of an aqueous solution of the monomers, followed by drying the resulting hydrogel, and grinding the dry polymers to a granular powder. The principal use of superabsorbent polymers is as a liquid absorbent in baby diapers, feminine hygiene products, and adult incontinence products. Smaller volumes are used in food packaging and in water‐blocking tapes for electrical and telecommunication cables. Total global usage of superabsorbent polymers in 2001 amounted to about 1093 kt.
Synchrotron Radiation
Authors: Bras Wim
Published: October 2003

Over the last decades it has become possible to perform x‐ray scattering experiments at SR beamlines. The superior qualities of the x‐ray beams generated at these sources, combined with technological developments in position‐sensitive detector systems, has made time‐resolved x‐ray experiments possible. Polymer research has benefited in many ways from the possibilities created by these instruments. With the latest generation of SR sources, offering even higher fluxes, better collimation, and wavelength tuneability, the opportunities for innovative research have been greatly expanded. It has become possible to utilize sample environments and technique combinations hitherto unthinkable. In this article several examples of possible experiments are discussed. Also some of the latest experiments at the frontier of new developments will be treated to give an indication what the future might bring.
Syndiotactic Polystyrene
Authors: Malanga Michael , Newman Thomas H.
Published: October 2003

Syndiotactic polystyrene is prepared from styrene monomer and organometallic catalysts. The material is a semicrystalline polymer with a crystallization rate high enough to make it practicable as an injection molding resin. The catalyst and polymerization chemistry is based on monocyclopentadienyl titanium complexes generally in combination with methylaluminoxane. The polymer has a melting point of 270°C with an excellent balance of processability, solvent resistance, and dimensional stability. The polymer can be filled with glass reinforcement, impact modified, and rendered ignition resistant, providing a new set of properties for the engineering plastics industry to use in electronic, automotive, electrical, and other market areas.
Test Methods
Authors: Furches Barbara J.
Published: October 2003

Plastics testing covers analytical, thermal, physical, and environmental procedures for determining the composition, structure, as well as mechanical and other responses to a variety of environmental conditions of plastic materials. General uses of Fourier transform infrared, nuclear magnetic resonance, Raman, and X‐ray techniques are reviewed and illustrated with specific examples. Developments in neutron and X‐ray scattering techniques, as well as molecular weight determination techniques such as gel‐permeation chromatography and turbidimetric methods, are also covered. Thermal tests, thermogravimetric analysis, differential thermal analysis, differential scanning calorimetry, and dynamic mechanical analysis are all useful for understanding degradation and phase changes in polymers and their influence on material behavior. New techniques of atomic force microscopy and positron annihilation are allowing studies of the microstructure of polymers and free volume determinations. Several mechanical testing techniques are used in plastics for normal quality control testing and initial application screening of polymers. These tests and those used for more fundamental understanding of polymer response to stress, including fracture mechanics procedures, are referenced. Flammability tests commonly used for plastics include oxygen index, flammability ratings, and smoke generation. Work on the use of cone calorimeters to characterize behavior of plastics under fire conditions is also covered. Finally, environmental testing, chemical exposure, weathering, radiation, and biological agents are reviewed. Emphasis is given to test development or applications reported since 1990.
Thermoforming
Authors: Throne James L.
Published: October 2003

Thermoforming is a generic term for the art and science of forming commercial products by heating plastic sheet to a pliable state, pressing the sheet against a cool mold, holding the formed sheet against the mold until cool, and trimming the formed part from the web or skeleton surrounding it. About 4.55 million metric tons of product are thermoformed worldwide at a value of about US$35,000 million. Thermoforming is characterized as capable of forming many polymers, of forming large surface area‐to‐wall thickness parts of forming parts against single‐surface molds that can be made of many materials, and of using moderate forming temperatures and pressures. Thermoforming does not produce a part with walls of well‐controlled, uniform thickness, and produces trim, web, or skeleton that usually must be recycled to achieve competitive economics.

Thin‐gauge thermoforming represents about 75% of the product volume, with the major products being packaging and disposable containers. Heavy‐gauge thermoforming represents about 25%, with the major products being permanent or industrial products.

A typical thermoforming machine consists of a sheet‐handling system, at least one heating station, a forming press, a vacuum system, and a control system. A trim station may or may not be integral to the machine. In addition, the machine may have sheet‐prestretching capability, a pressure system, and mold‐cooling capability. Cast or machined aluminum is the common mold material. Plugs or mechanical pushing devices are usually made of lower‐thermal‐conductivity materials such as molded nylon, epoxy, wood, or syntactic foam.

Technically, thermoforming is three essentially separate sequential steps: sheet heating, stretching, and trimming. Radiation is the primary mode of sheet heating. Efficient heating relies on the specific absorption characteristics of long infrared wavelength energy by the polymer. Sheet stretching is biaxial deformation of the nonisothermal rubbery elastic or viscoelastic membrane achieved through differential pressure across the sheet surface. Trimming is mechanical cutting or breaking of the cooled plastic. This is usually achieved with steel rule dies, forged dies, or for heavy‐gauge parts, with bandsaws or numerically controlled multiaxis routers.

Of late, twin‐sheet forming has become economically competitive. Improved process controls are being used to form parts from highly filled and reinforced polymers.
UV Stabilizers
Authors: Cangelosi Frank A. , Davis Leonard H. , Gray Robert L. , Stretanski Joseph A. , Jakiela Dennis J.
Published: October 2003

The beneficial effects of the major classes of light stabilizers are reviewed from a theoretical perspective as well as through practical application examples. The use of UV absorbers, hindered amine light stabilizers, other stabilizer types, and combination systems to reduce aesthetic as well as physical property deterioration due to UV exposure is discussed. Continued research on both the theoretical and practical aspects of polymer light stabilization will provide the basis for the successful development of new UV‐stabilized plastics and coatings formulations.
Vibrational Spectroscopy
Authors: Hsu Shaw Ling
Published: October 2003

This article presents various applications of vibrational spectroscopy for analysis of polymer structure. The relative merits of vibrational spectroscopy versus other techniques for characterization of polymer structure are discussed. Special emphasis is given to analysis of chain configuration, conformation, interchain interactions, crystallization behavior, and crystalline region size. Experimental data combined with data provided by normal coordinate analysis were utilized in analysis of spectroscopic features associated with disordered chains. Specialized topics such as amount of free volume, phase transformation, microspectroscopy, segmental orientation, and surface analysis are presented. Analysis of structural dynamics using double modulation spectroscopy and time resolved spectroscopy is also addressed.
Vinyl Alcohol Polymers
Authors: Marten F. L.
Published: October 2003

Poly(vinyl alcohol) is a highly crystalline polyhydroxy polymer produced by the hydrolysis of poly(vinyl acetate) because the vinyl alcohol monomer is not available. The polymer is water‐soluble and possesses excellent tensile strength, abrasion resistance, and superior oxygen‐barrier properties. PVA has excellent emulsification and protective colloid properties. Solvent, oil, and grease resistance are matched by few other polymers.

Poly(vinyl alcohol) undergoes chemical reactions in a manner similar to other secondary polyhydroxy alcohols, and is fully biodegradable. The polymer is considered a nonhazardous material according to the American Standard for Precautionary Labeling of Hazardous Industrial Chemicals.

Industrial applications of poly(vinyl alcohol) are all based on and limited by the use of water solutions. The polymer is not considered thermoplastic as the degradation temperature is below the melting point.

Poly(vinyl alcohol) is commercially available in granular and powdered form. Grades include both fully hydrolyzed and partially hydrolyzed products. A wide variety of molecular weight and hydrolysis is commercially available.

Major end uses include textile sizing, adhesives, protective colloid for emulsion polymerization, paper coating, cement and mortar additive, poly(vinyl butyral), fibers, and films.
Vinyl Chloride Polymers
Authors: Allsopp Michael W. , Vianello Giovanni
Published: October 2003

This article covers the uniqueness and versatility of this high tounage thermoplastic. The unique morphology of PVC is covered in detail and related to both its polymerization and production processes and also to its subsequent processing at the customer end. Each of the main polymerization processes of suspension, mass, and emulsion are described in detail with particular emphasis on how the morphology of each different product is created. Other aspects such as environmental protection, quality and testing, processing, and economic aspects complete the story of this fascinating polymer.
Vinylidene Chloride Polymers
Authors: Wessling R. A. , Gibbs D. S. , Obi B. E. , Beyer D. E. , DeLassus P. T. , Howell B. A.
Published: October 2003

Vinylidene chloride is a versatile monomer used primarily for making vinylidene chloride copolymers. These copolymers are mostly used in food packaging to provide a good barrier to mass transport. Most applications rely on the low permeation of oxygen, carbon dioxide, and water vapor. However, the polymers have also been shown to have good barrier to flavors and aromas. Thus, a barrier layer of one of these copolymers in a package structure not only prevents spoilage of the food item but prevents flavor “scalping” on the supermarket shelf. These copolymers are available in three forms. First, resin for extrusion into film or sheet represents the largest segment. This includes monolayer and coextruded film and coextruded sheet. Second, a number of emulsion resins are used for solution applications. A thin layer is coated onto a substrate. Third, copolymer latexes are used for paper coatings, etc. The coatings from solution or latex dry clear. Vinylidene chloride homopolymer does not have commercial application because its melting temperature is too high to permit extrusion without degradation, and it does not dissolve in a suitable solvent for coating.
Viscoelasticity
Authors: McKenna Gregory B.
Published: October 2003

A broad view of polymer viscoelasticity is presented. The article first discusses the basic definitions of stress and strain and the material modulus and compliance properties that relate the two in linear elasticity theory. The time‐dependent analogues in viscoelasticity are presented. The beginnings of polymer viscoelasticity concepts are then presented by building mechanical analogues of springs (elastic) and dashpots (viscous) elements that can capture the general features of polymeric behavior. A brief discussion of the elastic–viscoelastic correspondence principle is also provided. The general viscoelastic response of polymeric materials is presented by emphasizing the amorphous state and how the isochronal modulus changes with temperature. This is analyzed within the context of time–temperature superposition ideas and the Williams, Landel, and Ferry equation. In particular, it is interesting to divide the behavior into that below and far above the glass‐transition temperature. In the former case the local segmental motions of the polymer dominate behavior, while in the latter the long‐chain nature of the polymer dominates behavior. Molecular rheology ideas are briefly presented where the idea of the chain length or molecular weight dependence of the viscosity is introduced. This is extended by considering the scaling of viscosity and plateau modulus due to concentration as well as the introduction of time–concentration superposition principles similar to time–temperature principles.

The nonlinear rheological response of polymers far above the glass‐transition temperature is handled within a combined framework of the phenomenological K‐BKZ model and the Doi–Edwards (DE) tube model, which is based on the reptation ideas of de Gennes. The K‐BKZ framework is particularly useful because it looks much like time‐dependent finite elasticity theory that has been widely and successfully applied to rubber network polymers. Extensive discussion is presented of the comparison between theory and experiment of both K‐BKZ and DE models for polymer nonlinear viscoelastic behavior in the melt and solution states. Below the glass‐transition temperature, measurements of the nonlinear viscoelastic response are examined within the framework of the BKZ model, but also considering compressibility. Emphasis is given to torsional experiments in which both the torque and the normal force are measured. This exposition is followed by a description of several other nonlinear viscoelastic models that have been used for describing solid polymers. This article ends with a brief mention of plasticity models for the behavior of polymeric solids.