bluuebunny/crossref_metadata_2025_split huggingface dataset:
Olefin Fibers
Authors: Wust Carl J. , Gammelgaard Erik Grann 
Published: July 2004

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

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

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

AbstractPolypropylene is one of the most widely used thermoplastics, accounting for one sixth of total consumption of polymeric materials. Many automobiles, textiles, appliances, and other everyday items contain substantial amounts of these polymers. The ability to manufacture a broad variety of polypropylenes having properties tailored for specific applications is the primary factor in its widespread use. Polypropylene is a polymer whose stereoregularity can be controlled, and it exhibits a spectrum of structural variations, because of the ability to control the manner in which the asymmetrum monomer is incorporated into the growing chain, and through the use of comonomers, usually ethylene, which is often used to provide impact‐modified or lower melting polymers. The types of polymers produced, chain‐structural parameters which can be varied and means to characterize them, morophology, thermodynamic properties, processing methods, end use properties, and applications are discussed.Highly stereoselective Ziegler–Natta catalyst are primarily used to produce polypropylene and are the basis for most modern propylene polymerization processes. The historical development of these catalysts, from the early TiCl3systems to the modern, high yield MgCl2‐supported systems, including proposed polymerization mechanisms, are discussed. These catalysts enabled the evolution of these polymerization processes from the early slurry process to the current liquid monomer or gas‐phase processes. Metallocene catalysts have increasingly been an area of emphasis and have provided further commerical advances recently. Most major polymerization process in use today are discussed, with the most notable being the Spheripol and Unipol process. Key input into these polypropylene technologies and economics are the technology and infrastructure associated with propylene monomer. The large expansion in polypropylene production in the late 1980s was facilitated by the availability of this newer, less costly polymerization technology. This expansion, well in excess of growth in consumption, caused a dramatic reduction in polypropylene prices in the 1990s, most dramatically in the Far East, where few polypropylene plants existed outside Japan before 1985. Current economic prospects and associated industry trends are discussed.
Rubber Chemicals
Authors: Cohen Martin P. , D'Sidocky Richard M. 
Published: July 2004

AbstractThis article presents recent developments in the field of rubber chemicals, including non‐nitrosamine curatives, reversion‐resistance curatives, silica‐to‐rubber coupling agents, and nonstaining and persistent antidegradants for enhanced performance.Rubber processing chemicals are used extensively to impart performance and processability to rubber products. The rubber compound is described as a mixture of one or more rubber polymers (elastomers) with a combination of fillers, oils, and rubber chemicals. The compound, once vulcanized, provides technologically useful properties, such as may be applied to tires, hoses, belts, tracks, and a variety of mechanical goods.Vulcanization systems and antidegradants are dominant the classes of rubber chemicals because the largest class of rubbers used in the industry (the so‐called general‐purpose rubbers) require cross‐linking by sulfur or other curatives to provide meaningful performance, and require protection from oxygen and ozone to provide meaningful service lifetimes.
Solid‐State Extrusion
Authors: Beygelzimer Y. E. , Beloshenko V. A. 
Published: July 2004

AbstractSolid‐state extrusion (SSE) is a method for attaining a highly oriented state of polymers, and is based on polymer deformation at temperatures just below the polymer melting temperature, or for amorphous polymers just above the glass‐transition temperature mainly by extrusion through conical or slit dies.SSE is used for shape forming and structure modification of various polymer materials (homopolymers, polymer blends, filled polymer composites) and makes it possible to produce fibers, films, pipes, shapes including those of large cross section and of different configurations, possessing high strength–stress characteristics.In this article, much attention is given to the most known SSE versions—plunger extrusion and hydrostatic extrusion with the information on the influence of process controlling parameters on extrusion pressure, velocity of product exiting, value of extrudate swell, structure and properties of the processed material. There exists a region of controlling parameters where the process is stable; outside the region, the polymer flow is discontinuous, extrudate shape is imperfect and, finally, its failed.Two new techniques of SSE are presented in brief, namely the equal channel angular extrusion and the twist extrusion which, in contrast to the conventional ones, are based on polymer simple shear, not drawing. These techniques are found to be promising for structure modification of polymers.
Thermodynamic Properties of Polymers
Authors: Wunderlich Bernhard , Pyda Marek 
Published: July 2004

AbstractThe equilibrium properties of polymers and the changes occurring on going to nonequilibrium states are discussed. For example, the typical semicrystalline polymer is treated as a globally metastable structure of two or three nanophases with possible local equilibria (crystal/amorphous or crystal/amorphous/rigid amorphous). The transitions are explored experimentally by classical calorimetry and temperature‐modultated calorimetry. The heat capacity is taken as the basic thermodynamic property and linked to the different types of molecular motion in terms of small‐amplitude vibrational motion and large‐amplitude conformational motion. The low frequency vibrations are the skeletal vibrations and can be fitted to the low temperature heat capacities with one‐, two‐, and three‐dimensional Debye functions. The high frequency vibrations are treated as group vibrations, easily available as group vibrations from normal‐mode analyses of the polymer or related compounds. Data for almost 100 polymers are presented from the ATHAS data bank. The large‐amplitude, conformational motion can be linked to the deviation of the experimental heat capacity from the vibrational heat capacity and allowed to discuss the more mobile phases. The integral thermodynamic functions, enthalpy, entropy, and free enthalpy are then derived from the heat capacities and linked to the phase transitions and chemical thermodynamics (melting/crystallization, glass transition, mixing/demixing, and polymerization/depolymerization). The bibliography establishes the link to classical thermodynamics data and theory sources with 163 references.
N‐Vinylamide Polymers
Authors: Login Robert B. 
Published: July 2004

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

AbstractWater‐soluble (co)polymers represent a diverse class of macromolecules ranging from naturally occurring biopolymers such as polysaccharides and most polypeptides to wholly man‐made materials. Such materials have found a wide‐range of applications. In this article we detail the synthesis and solution characteristics of both natural and synthetic polymers. Emphasis is placed on polynucleotides, polypeptides, and polysaccharides for naturally occurring polymers, while the discussion regarding synthetic materials is divided into sections dealing with neutral, anionic, cationic, and zwitterionic species. Special attention is given to recent advances in synthetic methodologies which now allow the tailoring of synthetic materials with precisely controlled microstructures, predetermined molecular weights, narrow molecular weight distributions, and complex topologies.Finally, we detail some of the self‐assembly characteristics of both high molecular weight statistical copolymers and lower molecular weight block copolymers in aqueous media with an emphasis on those materials which undergo phase transitions and/or conformational changes in response to an applied stimulus.
Xylylene Polymers
Authors: Beach W. F. 
Published: July 2004

AbstractPinhole‐free coatings of outstanding conformality and thickness uniformity are produced by exposing a substrate to a controlled deposition of pure gaseous monomer through the unique chemistry ofp‐xylylene, which is thermally stable but very reactive toward polymerization with other like molecules, in a process known as vapor deposition polymerization (VDP). A high molecular weight coating of poly(p‐xylylene) (PPX) is produced. Recent VDP developments are stressed in the article.The convenient generation of the extremely reactive monomer is accomplished by thermal cleavage of its stable dimer,cyclo‐di‐p‐xylylene (DPX), commercially in the Gorham process. The PPXs formed as coatings in the Gorham process are referred to generically as parylenes. Parylene N, Parylene C, and Parylene D are polymer coatings produced by the Gorham process using the dimers DPXN, DPXC, and DPXD, respectively. These dimers are the feedstocks for the coating process. The Parylene C monomer, chloro‐p‐xylylene, has become the de facto performance standard owing to its room‐temperature volatility. VDP processes using means other than pyrolytic cleavage of DPX to generate reactive monomer, none practiced commercially, include photopolymerization and plasma polymerization, as well as imidization to produce polyimide films.Manufacture of commercial DPXN is through two routes: direct pyrolysis ofp‐xylene and the Hofmann elimination route. DPXC and DPXD are prepared from DPXN by chlorinating. Thermodynamic considerations of the parylene process by VDP are covered. The importance of the physical processes of condensation and diffusion in VDP are treated, as is the propagation reaction.VDP produces films of uniform thickness having excellent conformality and purity. Electrical properties merit their use in electronic construction. Barrier, spectral, and optical properties are also useful. Crystallinity determines important properties of mechanical strength at elevated temperatures and solvent resistance, which constitute the principal advantages of PPX materials. Uses include circuit boards, hybrid circuits, semiconductors, capacitors, the bathythermograph, medical uses (as in pacemakers), artifact conservation, and in laser fusion targets. They are also used as barrier coatings, in corrosion control, and as dry lubricants. The dimers present little concern in handling and storage to an experienced operator. In ancillary operations such as cleaning or adhesion promotion, suitable precautions given in manufacturers' Material Safety Data Sheets should be observed.
Drag Reduction
Authors: Singh Ram Prakash 
Published: July 2004

AbstractTurbulent drag reduction in fluid flow by additives has been an exotic field of research ever since its reported discovery in 1949. Various technical applications have been envisaged both for polymeric and surfactant drag reduction. Some successful applications include increased flow of oil and other fluids through pipelines, improved fire fighting and irrigation, improved flow in storm sewers, and flow augmentation by drag reducers in pipeline transport of sediments and slurries. Other possible applications include district heating circuits, industrial and agricultural sprays, and slow‐release fertilizers and pesticides. However, the mechanism of drag reduction still eludes exact explanation mainly because of the inability to characterize polymers, surfactants, and their interactions at molecular or micellar levels in turbulent flows.The main features of polymeric and surfactant homogeneous and heterogeneous drag reduction have been investigated by two‐component laser‐Doppler velocity meter in fully developed, well‐mixed, low concentration (1–2 ppm) drag‐reducing channel flows. Advances in computer technology have led to improved accuracies and reliability of experimental techniques and made possible direct numerical simulation of drag‐reducing turbulent flows. The role of extensional viscosity and elasticity of drag reducers is being keenly debated for the origin of drag reduction in theoretical and experimental investigations. A better understanding is emerging. Some synergistic effects have been observed in combining passive drag‐reducing devices such as riblets with polymers surfactants. Similar observations have been made in combination with microbubbles. This article provides an overview of the latest salient developments in materials, mechanisms, and applications in the field of polymeric drag reduction of various forms and geometries.
Mechanical Performance of Plastics
Authors: Brostow Witold , Singh Ram Prakash 
Published: July 2004

AbstractWe discuss methods of prediction of long‐term performance and reliability of polymer‐based materials from short‐term tests. The methods include prediction of slow crack propagation and also predictions based on correspondence principles including the stress–time correspondence. The amount of experimentation needed for reliable predictions is much lower than generally believed. For instance, experiments at two stress levels for a four‐phase polymer liquid crystal are sufficient for creation of a master curve. We cover briefly tribology, including friction, scratch resistance, and wear resistance. When appropriate, we illustrate mechanical and tribological processes by results of computer simulations.
Nanocomposites, Layer‐by‐Layer Assembly
Authors: Kotov Nicholas A. , Mamedov Arif A. , Guldi Dirk M. , Prato Maurizio , Wicksted James , Hirsch Andreas 
Published: July 2004

AbstractLayer‐by‐layer assembly with polyelectrolytes (LBL) is one of the most powerful methods of preparation of nanocomposites. The current practice and future prospects of LBL‐made materials is reviewed. One of the most fundamentally interesting and practically relevant applications of LBL is the preparation of ultrastrong materials. The mechanical failure of hybrid materials made from polymers and single wall carbon nanotubes (SWNT) is primarily attributed to poor matrix–SWNT connectivity and severe phase segregation. Both problems can be successfully mitigated when the SWNT composite is made following the protocol of layer‐by‐layer assembly. This deposition technique prevents phase segregation of the polymer/SWNT binary system, and after subsequent cross‐linking, the nanometer‐scale‐uniform composite with SWNT loading as high as 50 wt% can be obtained. The free‐standing SWNT/polyelectrolyte membranes delaminated from the substrate are exceptionally strong with tensile strength approaching that of hard ceramics. Considering the lightweight nature of SWNT composites the prepared free‐standing membranes can serve as unique components for a variety of long‐lifetime devices.
Tissue Engineering
Authors: Ma Peter X. 
Published: July 2004

AbstractTissue engineering, still in its infancy, has shown great promise in developing novel therapies to tissue losses and organ failures. Scaffolds play a pivotal role in tissue engineering. Biodegradable polymers are the primary choice of materials for tissue engineering scaffolds. In this article, the principles of tissue engineering are discussed in relation to polymer science and engineering. The most frequently used polymers in tissue engineering are briefly reviewed. These include synthetic and natural polymers for porous scaffolds and hydrogel scaffolds. Their structure and important properties in relation to scaffold function are discussed. Important polymer processing techniques in the context of scaffold fabrication are also reviewed. These include the textile technologies, particulate‐leaching techniques, phase separation techniques, rapid prototyping, and other novel 3‐D fabrication techniques.
Wood Composites
Authors: Matuana Laurent M. , Heiden Patricia A. 
Published: July 2004

AbstractThe term wood composites is a general one that describes a wide range of products having some combination of wood element(s) held together by an adhesive “binder.” The wood composites industry is growing rapidly from both a steadily increasing demand for existing products and an increasing demand for new products to be used in new applications. This article describes the types of wood elements and major wood adhesives that are employed by the wood composites industry today, and major wood composite products that are currently marketed. An overview of current research directions and the forces driving this research is also presented, including research into alternative adhesive systems, adhesive modifications, improved processes, and lignocellulosic alternatives to wood.
Poly(ethylene naphthalate) (PEN)
Authors: Sakellarides S. L. 
Published: July 2004

AbstractPoly(ethylene naphthalate) (PEN) is a thermoplastic polyester with performance properties superior to that of poly(ethylene terephthalate) (PET). With its higher stiffness, moisture, gas, and light barrier, as well as thermal, electrical, and chemical resistance, PEN extends polyester's application range into more demanding end uses in a variety of areas such as rigid and flexible packaging, industrial fiber, and film for electrical, light management, data storage, and imaging applications. This article summarizes PEN's key material properties, resin preparation and fabrication, and representative examples of end‐use applications published to date.
Photopolymerization, Free Radical
Authors: Cai Ying , Jessop Julie L. P. 
Published: July 2004

AbstractFree‐radical photopolymerizations, which use light energy to initiate chain‐producing reactions, have many advantages over thermal polymerizations, including solvent‐free systems, spatial and temporal control of initiation, and high speed processing capabilities. This article provides an overview of the components, kinetics, and applications of free‐radical photopolymerization systems. Two general classes of photoinitiator systems (unimolecular and bimolecular) are discussed, as well as systems that have been developed to meet the demands of specific applications. (Meth)acrylates, which are the most widely used monomers in photopolymerization processes, and other commercially important free‐radical monomers, are described. The kinetic treatment of free‐radical photopolymerizations is outlined, with special emphasis on the photoinitiation step and its impact on the rate of polymerization expression. Kinetic modeling concerns in reaction systems containing monomers with more than one reactive group and in systems utilizing specialized polymerization methods are also considered. Finally, applications for free‐radical photopolymers in the automotive, electronic, medical, optical, graphic arts, flooring, and furniture industries are presented. This article provides the scientist or engineer with fundamental considerations of free‐radical photopolymerizations, along with references for more advanced topical research.