bluuebunny/crossref_metadata_2025 huggingface dataset:
Rotational Isomerism and Structure of the 1-Butyl-3-methylimidazolium Cation in the Ionic Liquid State
Authors: Ozawa Ryosuke , Hayashi Satoshi , Saha Satyen , Kobayashi Akiko , Hamaguchi Hiro-o
Published: September 2003

The crystal structures of 1-butyl-3-methylimidazolium chloride [bmim]Cl and 1-butyl-3-methylimidazolium bromide [bmim]Br show that two rotational isomers, the TT form and the GT form, of the [bmim]+ cation exist in the crystalline state. A vibrational analysis based on a DFT calculation indicates that two characterstic Raman bands of crystalline [bmim]Cl and three of crystalline [bmim]Br can be used as marker bands of the rotational isomerism around the C7–C8 bond of the n-butyl group. The Raman spectra of liquid [bmim]BF4, in which both sets of marker bands are simultaneously observed, then prove that at least two rotational isomers of the [bmim]+ cation coexist in the ionic liquid state.
Synthesis of Highly Ordered Hybrid Mesoporous Material Containing Etenylene (–CH=CH–) within the Silicate Framework
Authors: Nakajima Kiyotaka , Lu Daling , Kondo Junko N , Tomita Ikuyoshi , Inagaki Shinji , Hara Michikazu , Hayashi Shigenobu , Domen Kazunari
Published: September 2003

A hybrid mesoporous material containing etenylene in a two-dimensional, hexagonally arranged mesoporous silicate framework with long-range symmetry is successfully synthesized. Quantitative analysis of the reactive etenylene groups within the silicate framework indicates that approximately 30% of the etenylene is exposed at the surface and is available for further modification.
A Novel Double-helical Assembly in Inclusion Crystals of Fumaropimaric Acid
Authors: Kato Kazuaki , Aburaya Kazuaki , Matsumoto Masatake , Tohnai Norimitsu , Miyata Mikiji
Published: September 2003

A crystal structure of the inclusion compound of fumaropimaric acid (FPA), a new host material, with 2-butanone reveals that the host framework is composed of novel double-helical supramolecular aggregates without hydrogen bonds between the intertwined helices.
Dependence of the Electrochemical Response of Ferritin on the Number of Iron Atoms at the Ferritin Core
Authors: Tominaga Masato , Taniguchi Isao
Published: September 2003

The well-defined redox reaction of ferritin was observed at an indium oxide electrode with a fully hydrophilic surface at a low concentration of ferritin solution (0–7 μmol dm−3). This was a diffusion-controlled electrode reaction process. Conversely, at a higher concentration of ferritin (7 μmol dm−3 <), ferritin was weakly adsorbed on the electrode surface. The electrochemical redox response of ferritin was strongly affected by the number of iron atoms at the core of the ferritin molecule.
In Situ X-ray Absorption Fine Structure Studies on the Structure of Nickel Phosphide Catalyst Supported on K-USY
Authors: Kawai Toshihide , Sato Shinsuke , Suzuki Shushi , Chun Wang-Jae , Asakura Kiyotaka , Bando Kyoko K , Matsui Takashi , Yoshimura Yuji , Kubota Takeshi , Okamoto Yasuaki , Lee Yong-Kul , Oyama Shigeo Ted
Published: September 2003

Local structure around Ni in a nickel phosphide catalyst supported on K-USY was investigated by an in situ X-ray absorption fine structure (XAFS) method during the reduction process of the catalyst and the hydrodesulfurization (HDS) reaction of thiophene. In the passivated sample, Ni phosphide was partially oxidized but after the reduction, 1.1 nm diameter Ni2P particles were formed with Ni–P and Ni–Ni distances at 0.218 and 0.261 nm, respectively, corresponding to those of bulk Ni2P. In situ XAFS clearly revealed that the Ni2P structure was stable under reaction conditions and was an active structure for the HDS process.
The Effects of Noise on Children at School: A Review
Authors: Shield Bridget M , Dockrell Julie E
Published: September 2003

This paper reviews research on issues relating to the effects of noise on children at school. Areas covered include factors affecting speech intelligibility in the classroom; the effects of environmental and classroom noise on children's academic performance; children's annoyance due to noise; and surveys of classroom noise levels. Consistencies and discrepancies between the results of various studies are highlighted. The paper concludes by outlining some current acoustic standards for classrooms.
On the Effect of Domed Ceiling in Worship Spaces: A Scale Model Study of a Mosque
Authors: Prodi Nicola , Marsilo Matteo
Published: September 2003

Though the importance of domes in worship buildings has been recognised since ancient times, their acoustic effects have not been entirely addressed by acoustics researchers. In addition to the known detrimental effects of late reflections and echoes, more complicated behaviour can be expected as a result of the coupling of the dome volume to the rest of the room. This investigation is focused on the impact of a dome on reverberation time. This is done using a scale model study of a typical mosque. The results show how the parameter is affected and indicate how the phenomenon might be quantified.
Churches as Auditoria: Analysis of Acoustical Parameters for a Better Understanding of Sound Quality
Authors: Magrini A. , Ricciardi P.
Published: September 2003

At the present time, music performances frequently take place in ancient religious buildings, and significant problems related to acoustic quality may occur. Measurement results obtained in 10 historically significant churches in the city of Genova, are examined. Experimental data obtained from research literature on auditoria and churches has been compared with the experimental results. A survey of the available theoretical models of the spatial distribution of the most significant acoustical parameters has been conducted, and the models most suitable for religious buildings have been applied to the churches selected. A comparison between theoretical models and experimental data is presented. A case study on the effects of permanent and non permanent acoustical treatment, without significantly changing the architectural characteristics, is presented for one of the churches selected. The results of the measurements, at various phases of the acoustical treatment, and some software simulations are presented.
Evaluation of controller performance—use of models derived by subspace identification
Authors: Bezergianni S. , Georgakis C.
Published: September 2003

A new approach is presented for the estimation of the controller, process, and disturbance models necessary for the calculation of the relative variance index, which was introduced in an earlier paper (Control Eng. Practice2000;8:791–797), for the performance of SISO controllers. It involves the use of dynamically, sufficiently rich segments from the normal operating data and the use of the subspace identification technique to estimate the systems mentioned above. This approach improves the estimation accuracy of the performance index in relation to the method presented previously. The estimated models enable the comparison of the present controller performance with that of optimally tuned PI or IMC controllers. This helps identify the potential benefits of either retuning or redesigning the assessed controller. Copyright © 2002 John Wiley & Sons, Ltd.
Determining controller benefits via probabilistic optimization
Authors: Zhou Y. , Forbes J. F.
Published: September 2003

For the most part, process control research has focussed on the synthesis and tuning of controllers, which has provided a plethora of techniques that can address virtually any application. With each new control technique, a steady stream of ‘successful’ application results are generated and reported. Recently, a considerable number of control researchers have turned their attention to assessing the performance of installed control systems and to the diagnosis of controller performance problems. Despite successes in the areas of controller synthesis, tuning and performance analysis, almost no research has addressed the fundamental issue of determining whether the economic performance gains that are expected accrue from a proposed process control project are sufficient to justify its execution. The work presented here proposes an optimization‐based technique for calculating the expected economic performance of a given control system; a method, which is analogous to analysis of variance, for determining the expected economic benefit that will arise from a particular controller improvement effort; and a sensitivity analysis approach for determining the effect of specific assumptions on control system improvement decisions. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of multivariable controllers using degree of freedom data
Authors: Harris T. J. , Yu W.
Published: September 2003

Most approaches for monitoring, diagnosis and performance analysis of multivariable control loops employ time series methods and use non‐parametric statistics to analyse the process inputs and outputs. In this paper, we explore the use of a discrete variable that summarizes the status of the constraint set of the controller to analyse the long run behaviour of control systems. We introduce a number of waiting and holding time statistics that describe the status of this data, which we call the degree of freedom data. We demonstrate how Markov Chains might be used to model the status of the degree of freedom data. This model‐based approach has the potential to provide considerable insight into the behaviour of a model based control scheme with relative ease. We demonstrate the methodologies on simulated and industrial data. Copyright © 2003 John Wiley & Sons, Ltd.
A comparison of two feedforward control structure assessment methods
Authors: Petersson M. , Årzén K.‐E. , Hägglund T.
Published: September 2003

The most common loop in an industrial plant is a SISO‐loop with a PI(D) controller. If the loop is affected by disturbances, these can be handled by adding a feedforward control action. In an industrial control system there are many measured signals, apart from those of the loop, available. The question we address in this article is how to select the feedforward variable out of the available measurements. A comparison is made of two methods for feedforward control structure assessment. The first is a method based on comparing the actual variance with the minimum achievable variance, and thus the contribution to the overall variance. The second is a method for evaluating deterministic additive disturbances and estimate where they enter in the process. The methods complement each other and show that assessment methods should be handled with care, since they are mostly designed for different control objectives. Copyright © 2003 John Wiley & Sons, Ltd.
A segmentation‐based method for detection of stiction in control valves
Authors: Stenman A. , Gustafsson F. , Forsman K.
Published: September 2003

A method for detecting static friction (stiction) in control valves is proposed. The method is model‐based and is inspired by ideas from the fields of change detection and multi‐model mode estimation. Opposed to existing methods only limited process knowledge is needed and it is not required that the loop has oscillating behaviour. The advantage of the method is illustrated in both numerical simulations and evaluations on real loop data. Copyright © 2003 John Wiley & Sons, Ltd.
Process and controller performance monitoring: overview with industrial applications
Authors: Hoo K. A. , Piovoso M. J. , Schnelle P. D. , Rowan D. A.
Published: September 2003

Complex processes depend on regulatory control systems to operate. Changes made to the sensor system and the process itself as well as the natural degradation over time of the equipment may cause some controllers' and process performance to suffer. Since there are hundreds of controllers in most complex processes, it is virtually impossible to monitor their performance manually. This work reviews the state‐of‐the‐art in controller performance monitoring including both feedforward and feedback control. The experiences of the DuPont Company in the deployment of a system for performance monitoring are presented. Information as to how such a monitoring system is implemented in the operation of a chemical process and examples of its operation are included. Copyright © 2003 John Wiley & Sons, Ltd.
Performance assessment of level controllers
Authors: Horton E. C. , Foley M. W. , Kwok K. E.
Published: September 2003

A variety of techniques have been developed for the assessment of industrial control loops. These involve computation of an index which compares some measure of controlled variable performance (e.g. variance of distillate impurity) to the best achievable. Such methods are generally not suitable for the assessment of surge tank level controllers, for which the behaviour of the manipulated effluent flowrate is of greater concern. This paper introduces a flow smoothing performance index for the assessment of surge tank level loops against an averaging level control standard. Several control schemes were evaluated as potential flow smoothing benchmarks through application to simulated, pilot‐plant and industrial data sets. An optimal PI regulator was recommended as the default performance standard for industrial level control loops. A novel feature of this assessment technique is that it not only measures the performance of the installed controller, but also specifies new settings for the PI tuning parameters. Copyright © 2003 John Wiley & Sons, Ltd.
A relative performance monitor for process controllers
Authors: Li Q. , Whiteley J.R. , Rhinehart R.R.
Published: September 2003

A monitor is developed to automatically detect poor control performance. It provides a measure (relative performance index—RPI) of a control‐loop performance relative to a reference model of acceptable control. The reference model simulates the controlled variable output of a user‐defined, acceptably tuned control loop. The inputs to the reference model are the setpoints (same as the true plant) and the disturbances (estimated from the measurements). The monitor uses routine plant operation data only. Pending ability to obtain temporally accurate process models, and the validity of process measurements, simulations and experiments show that the monitor can detect the poor control performance caused by improper controller parameter values or changes in plant characteristics, and can distinguish it from poor performance caused by external disturbances. Copyright © 2003 John Wiley & Sons, Ltd.
Controller performance assessment in set point tracking and regulatory control
Authors: Thornhill N.F. , Huang B. , Shah S.L.
Published: September 2003

Recent critiques of minimum variance benchmarking for single‐input–single‐output (SISO) control loops have focused on the need for assessment of performance during set point changes and also on the need to pay attention to the movements in the manipulated variable. This paper examines factors that influence the minimum variance performance measure of a SISO control loop. It discusses the reasons why performance during set point changes differs from the regulatory performance during operation at a constant set point. The results demonstrate how regulatory performance is influenced by the nature of a disturbance, and that correlation of signals within a control loop can indicate whether the disturbance is random or deterministic. The paper is illustrated with simulated, experimental and industrial examples. Copyright © 2003 John Wiley & Sons, Ltd.
Laser Surface Alloying with a CO2 Laser: Surface Hardening of AlSl 4135 H Chromium‐Molybdenum Steel
Authors: Hlawka F. , Cornet A.
Published: September 2003

What is the best additive for laser surface hardening of a common Cr/Mo steel? The authors have investigated this problem in detail. Carbide injection results in cracks and a pullout tendency by wear tests, boron is highly effective, boron carbides need concomitant addition of zirconia to avoid cracking. The problems involved in remelting such coatings are also discussed. The Figure shows the interface between a boron carbide precoating on AISI 4135 M steel.
Preparation and Characterization of Uniformly Sized Sub‐micrometer Spherical Silica/Organic Polymer Hybrid Particles
Authors: Xing X.‐s. , Li R.K.‐Y. , Shek C.‐h.
Published: September 2003

Hybrid particles with a core‐shell structure, consisting of a silica core and a polyvinyl alcohol (PVA) shell, (see Figure for an SEM image of a particle material of this type), were fabricated via a two‐step sol‐gel process. The PVA molecular chains are probably physically adsorbed onto the surface of silica cores by hydrogen bonds and van der Waals forces.
Electrical Conductivity of In‐situ TiN/O′‐Sialon Multiphase Nanoceramics
Authors: Yang J. , Xue X. , Xie P. , Liu X. , Wang W.
Published: September 2003

A new multphase nanoceramic, in‐situ TiN/ O′‐Sialon was in‐situ synthesized by pressureless sintering of Si3N4, SiO2, and Al2O3 and nanoparticle TiO2. The incorporation of TiN should significantly improve the electrial conductivity of the material. The purpose of the present work is systematically to study the electroconductivity of in‐situ TiN/O′‐Sialon multiphase nanoceramic at various temperatures and to explore its conduction mechanism.
Semi‐Solid Metal Processing of Aluminum Alloy A356 and Magnesium Alloy AZ91: Comparison Based on Metallurgical Consideration
Authors: Kleiner S. , Ogris E. , Beffort O. , Uggowitzer P.J.
Published: September 2003

Thixocasting or rheocasting of AZ and AM magnesium alloys continues to be a problematic case in semi‐solid processing. The comparison with the aluminum thixo alloy A 356 shows that the metallurgical and physical properties of the Mg alloy AZ 91 are little compatible with this technology (see Figure for the morphology of the eutectic in AZ 91): The conclusions from this study are of fundamental importance for future developments in this field of research.
Ceramic Films Produced by a Gel‐Dipping Process
Authors: Santacruz I. , Ferrari B. , Nieto M.I. , Moreno R.
Published: September 2003

A novel method for manufacturing self‐supporting ceramic films is based on the use of aqueous suspensions containing low concentrations of a biopolymer (carrageenan) and the formation of the film by immersion of a graphite substrate into the ceramic suspension heated at 60 °C. A film is obtained by dipping after cooling at RT; burning out graphite during sintering leaves homogeneous, dense, and self‐supported films (see Figure for an SEM image).
High‐Speed Deformation Processing of a Titanium Alloy
Authors: Tamirisakandala S. , Yellapregada P.V.R.K. , Medeiros S.C. , Frazier W.G. , Malas J.C. , Dutta B.
Published: September 2003

The deformation rate is the critical parameter for the phase transforming mechanism and subsequently the morphology of Ti‐Al‐V alloys, which in turn determines the feasibility of high‐speed deformation. The evolution of defect‐free equiaxed microstructures is due to dislocation‐induced heterogeneous nucleation and growth. The Figure shows a microstructure of a Ti‐6Al‐4V specimen deformed at 1000 °C in a backscattered SEM image.
Electrochemical Fabrication of Nickel Manganese Gallium Alloy Powder
Authors: Muir Wood A.J. , C Copcutt R. , Chen G Z. , Fray D.J.
Published: September 2003

Ferromagnetic nodules of the stoichiometric alloy Ni2MnGa were obtained by the electrochemical reduction of a suitable mixture of nickel, manganese, and gallium oxide powders in molten calcium chloride. The product exhibits ferromagnetic shape memory properties ready to be used in a composite capable of enduring high strain in a magnetic field. The Figure shows an SEM image of the cross section of lightly sintered pellets of mixed powders of NiO, MnO2, and Ga2O3 (molar ratio 2/1/1) after electrolysis.
An Orthotropic Magnesium–Carbon Composite as a Lightweight Heat‐Guide Material with High Specific Stiffness and Radiation Transparency
Authors: Vaucher S. , Beffort O. , Kübler J. , Lehner F.
Published: September 2003

A metal matrix composite with spectacular properties has been synthesized: high thermal conductivity, stiffness, good machinability, low toxicity and high radiation transparency are the outstanding features that characterize the orthotropic magnesium‐carbon composite presented in this article. The Figure shows a cross‐sectional optical image of the material.
Computing Fibers: A Novel Fiber for Intelligent Fabrics?
Authors: Clemens F. , Wegmann M. , Graule T. , Mathewson A. , Healy T. , Donnelly J. , Ullsperger A. , Hartmann W. , Papadas C.
Published: September 2003

This communication describes a possible path for transition from a wearable computer to a fiber computer in which digital processing power is integrated directly into textiles via circuits on individual fibers. Three different classes of computing fiber substrate (active, passive, and intermediate) are discussed and some technologies for their manufacture are reviewed. It is shown here that with two of these techniques it is possible to develop new substrates for the semiconductor industry. Using an silicon‐on‐insulator (SOI) process, polycrystalline silicon fibers with a length of 42 mm have been successfully produced at NMRC in Ireland. These fibers are 35 μm wide and 1 μm thick. Silicon carbide (SiC) and silicon dioxide (SiO2) endless fibers (subsequently cut in to 20 cm lengths) have also been produced by extrusion. After sintering, this method yielded polycrystalline SiC fibers and pure amorphous SiO2 glass fibers. For many future applications, fiber computing appears to be a possible key to success. The computing power offered by such fibers may be combined with additional in‐ and output functions by weaving fiber‐based sensors and piezoelectric materials into textiles.
Ductility in Intermetallic Compounds
Authors: Russell A.M.
Published: September 2003

Intermetallic compounds are comprised of two or more metallic elements, but unlike ordinary metals, they have bonding that is part metallic, part covalent, and part ionic. Because of their mixed bonding, they are often lighter, stronger, stiffer, and more corrosion‐resistant than ordinary metals, particularly at high temperatures. Yet their uses are limited because they are usually brittle at room temperature (RT), making them difficult to fabricate and vulnerable to fracture. These materials hold great promise to improve efficiency in the transportation, electric power generation, and chemical process industries; however, persistent problems with low ductility and poor fracture toughness have severely limited their use in engineering systems. This article presents an overview of the progress in improving the RT ductility and fracture toughness of intermetallic compounds and describes prospects for their near‐term engineering use.
Advanced New Lightweight Materials: Hollow‐Sphere Composites (HSCs) for Mechanical Engineering Applications
Authors: Baumeister E. , Klaeger S.
Published: September 2003

“Lightweight” is a major trend in machine tool design to ensure higher speed and higher acceleration of elements, which results from state‐of‐the‐art technology, such as the new linear drive and the control system.[1] Research is being carried out in institutes worldwide into lightweight construction by either design and/or choice of material. One type of advanced lightweight engineering material to reduce the mass of the moving parts of machine tools is hollow‐sphere composites. Investigations of their thermal and mechanical properties show the superior quality of HSCs compared with alternative materials. Example applications of hollow‐sphere composites include the table of a milling machine and robot arms.
Progress in Polypropylene Nanocomposite Development
Authors: Leuteritz A. , Pospiech D. , Kretzschmar B. , Willeke M. , Jehnichen D. , Jentzsch U. , Grundke K. , Janke A.
Published: September 2003

This article summarizes some of the highlights of newest developments in polypropylene (PP) clay nanocomposite research. Different property improvements, including mechanical performance enhancements, achieved by melt compounding of organoclay materials with PP and/or PP‐g‐MA are presented.
Naturstoffhybride als neue Leitstrukturen bei der Wirkstoffsuche
Authors: Tietze Lutz F. , Bell Hubertus P. , Chandrasekhar Srivari
Published: September 2003

Bei der Entwicklung neuer Wirkstoffe spielen Naturstoffe eine wichtige Rolle. Besondere Bedeutung kommt ihnen auf den Gebieten Antiinfektiva, Krebstherapeutika und Immunsuppressiva zu. Die Zahl der natürlich vorkommenden Substanzen ist jedoch begrenzt, wohingegen durch die Kombination von Teilen unterschiedlicher Naturstoffe Millionen von Naturstoffhybriden mit vielfältigen und verschiedenartigen Eigenschaften zugänglich sein sollten. Dieser Ansatz ist für die Entwicklung neuer Leitstrukturen für sowohl medizinische als auch agrochemische Anwendungen sehr vielversprechend, da die biologische Aktivität dieser Hybride in vielen Fällen diejenige der entsprechenden Mutterverbindungen übersteigt. Der Vorteil dieses Konzepts gegenüber einem auf dem Zufall beruhenden kombinatorischen Ansatz besteht in der Vielfalt und der inhärenten biologischen Aktivität der gebildeten Hybride.
Titelbild: Catalytic Reforming of Oxygenated Hydrocarbons for Hydrogen with Low Levels of Carbon Monoxide (Angew. Chem. 34/2003)
Authors: Davda Rupali R. , Dumesic James A.
Published: September 2003

CO‐armen Wasserstoff liefert das Reforming sauerstoffhaltiger Verbindungen wie Ethylenglycol in Wasser mit einem Pt‐Katalysator. Die Ausdehnung der Gasblasen, die sich während des Prozesses bilden, führt zur Verringerung der H2‐ und CO2‐Partialdrücke. Dadurch verschiebt sich das Wassergasgleichgewicht, und die CO‐Konzentration sinkt. Auf diese Weise kann für Brennstoffzellen geeignetes H2 erhalten werden. Weitere Informationen finden Sie in der Zuschrift von J. A. Dumesic und R. R. Davda auf S. 4202 ff.
Natural Product Hybrids as New Leads for Drug Discovery
Authors: Tietze Lutz F. , Bell Hubertus P. , Chandrasekhar Srivari
Published: September 2003

Natural products play an important role in the development of drugs, especially for the treatment of infections and cancer, as well as immunosuppressive compounds. However, the number of natural products is limited, whereas millions of hybrids as combinations of parts of different natural products can be prepared. This new approach seems to be very promising in the development of leads for both medicinal and agrochemical applications, as the biological activity of several new hybrids exceeds that of the parent compounds. The advantage of this concept over a combinatorial chemistry approach is the high diversity and the inherent biological activity of the hybrids.
Cover Picture: Catalytic Reforming of Oxygenated Hydrocarbons for Hydrogen with Low Levels of Carbon Monoxide (Angew. Chem. Int. Ed. 34/2003)
Authors: Davda Rupali R. , Dumesic James A.
Published: September 2003

CO‐poor hydrogen can be produced by reforming oxygenates, such as ethylene glycol, in water over Pt catalysts. The expansion of the gas bubbles formed in the process by the vaporization of water results in a decrease in the partial pressures of H2 and CO2, thereby favoring the water–gas shift and lowering the CO concentration. This process leads to the production of fuel‐cell‐grade H2 at high pressures. For more information see the Communication by J. A. Dumesic and R. R. Davda on page 4068 ff.
Use of some plant wastes as fillers for polypropylene
Authors: Eboatu A. N. , Akpuaka M. U. , Ezenweke L. O. , Afiukwa J. N.
Published: September 2003

Palm kernel shell and the palm fruit pulp fiber were used as additives for polypropylene. The mechanical properties of the polymer, namely, tensile strength, impact strength, surface hardness, and flexural modulus were remarkably enhanced. This was attributed to the fact that these solid wastes functioned as reinforcing fillers through bonding interactions and stress‐sharing mechanisms. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1447–1452, 2003
Rate and amount of cellulose synthesis in developing fibers of Gossypium arboreum and Gossypium hirsutum cotton
Authors: Moharir A. V. , Bodas Manish , Vashisth Ananta
Published: September 2003

Cotton fiber cellulose synthesis and cellulose content at various post anthesis maturity stages of boll' development were studied in sixteen cotton varieties of Gossypium arboreum and Gossypium hirsutum species, grown in the 2001 crop year in New Delhi, under identical agro‐climatic conditions. Cellulose content was estimated using Updegraff's method. Field matured seed cotton was harvested at the end of the crop season and ginned fibers were subjected to physical testing in an AFIS‐HVI facility. X‐ray orientation parameters were computed from the normalized azimuthal diffracted X‐ray intensity scans of (002) reflections. Simple correlations were worked out among various parameters measured. Cotton varieties were indeed observed to vary in their synthesized cellulose content and such differences are genetically inherent. Varieties of Gossypium arboreum synthesized less cellulose compared to the Gossypium hirsutum cultivars, although the rate of cellulose synthesis within each variety, regardless of species, was observed to be practically uniform at any five‐day interval. The range of variation in cellulose content was observed to be more than 260%. Uniformity ratio, HVI tenacity and average leaf area were positively correlated with cellulose content. X‐ray angles of 40% and 50% correlated significantly with a negative cellulose content, (thereby) indicating an increased orientation of cellulose crystallites to the fiber axis, with a greater amount of cellulose synthesized. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1453–1462, 2003
Fractal approach for modeling the morphology evolution of olefin polymerization with heterogeneous catalysts
Authors: Huo C. , Ren X. H. , Liu B. P. , Yang Y. R. , Rong S. X.
Published: September 2003

Fractal theory and methodology were used to investigate the morphology of titanium–magnesium‐supported polyethylene catalysts and their relevant polymer particles. Through an analysis of the submicrostructures using scanning electron microscopy images, the surface fractal dimensions of the related particles were estimated with the box‐counting method. With consideration given to the fact that the growth process of a polymer is an evolving fractal process, which is controlled on the one hand by the initial conditions, including the initial fractal dimensions of the catalysts and the initial reaction conditions, and on the other hand by the previous morphology characteristics of the system, a novel polymerization fractal growth model was constructed. The simulation results showed good agreement with the experiment data. Moreover, the morphology evolution with the prepolymerization technique was predicted, and it was suggested that the duration of polymerization was 10–30 min. It was proven that the use of the surface fractal dimension as an important parameter describing the surface morphologies of the particles, either of catalysts or polymers, was real and effective. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1463–1470, 2003
Control of shrinkage and final conversion of vinyl ester resins cured in low‐temperature molding processes
Authors: Cao Xia , Lee L. James
Published: September 2003

Vinyl ester resin is a major thermoset polymer used in low‐temperature composite manufacturing processes such as the Seemann composite resin infusion‐molding process (SCRIMP). Volume shrinkage and residual styrene are important concerns for composites produced in such processes. A low‐shrinkage additive (LSA) is a typical agent added to control the volume shrinkage of vinyl ester resins during molding. In this study, the effects of LSA content and the temperature profile (the temperature gradient and peak temperature) on the volume shrinkage control of a vinyl ester resin were investigated. The reaction kinetics of the resin system were also studied. We achieved good volume shrinkage control if we raised the curing temperature slowly to allow sufficient time for phase separation and if the curing temperature reached a high value after phase separation to allow microvoid formation. On the basis of experimental results, we designed an improved SCRIMP to increase resin conversion, reduce resin shrinkage, and produce composites with better properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1486–1496, 2003
Preparation and characterization by radiation of poly(vinyl alcohol) and poly(N‐vinylpyrrolidone) hydrogels containing aloe vera
Authors: Park Kyoung Ran , Nho Young Chang
Published: September 2003

In these studies, hydrogels for wound dressings were made from a mixture of aloe vera and poly(vinyl alcohol) (PVA)/poly(N‐vinylpyrrolidone) (PVP) by freezing and thawing, γ‐Ray irradiation, or a two‐step process of freezing and thawing and γ‐ray irradiation. We examined the physical properties, including gelation, water absorptivity, gel strength, and degree of water evaporation, to evaluate the applicability of these hydrogels for wound dressings. The PVA:PVP ratio was 6:4, the dry weight of aloe vera was in the range 0.4–1.2 wt %, and the solid concentration of the PVA/PVP/aloe vera solution was 15 wt %. We used γ radiation doses of 25, 35, and 50 kGy to expose mixtures of PVA/PVP/aloe vera to evaluate the effect of radiation dose on the physical properties of the hydrogels. Gel content and gel strength increased as the concentration of aloe vera in the PVA/PVP/aloe vera gels decreased and as radiation dose increased and the number of freeze–thaw cycles was increased. The swelling degree was inversely proportional to the gel content and gel strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1477–1485, 2003
Toughening of epoxy resins by hydroxy‐terminated, silicon‐modified polyurethane oligomers
Authors: Bhuniya Sankarprasad , Adhikari Basudam
Published: September 2003

Epoxy resins are among the most versatile engineering structural materials. A wide variety of epoxy resins are commercially available, but most are brittle. Several approaches have been used to improve the toughness of epoxy resins, including the addition of fillers, rubber particles, thermoplastics, and their hybrids, as well as interpenetrating polymer networks (IPNs) of acrylic, polyurethane, and flexibilizers such as polyols. This last approach has not received much attention; none of them have been able to suitably increase resin toughness with out sacrificing tensile properties. Therefore, in an attempt to fill this gap, we experimented with newly synthesized hydroxy‐terminated silicon‐modified polyurethane (SiMPU) oligomers as toughening agents for epoxy resins. SiMPU oligomers were synthesized from dimethyl dichlorosilane, poly(ethylene glycol) (weight‐average molecular weight ∼ 200), and toluene 2,4‐diisocyanate and characterized with IR, 1H‐NMR and 13C‐NMR, and gel permeation chromatography. The synthesized SiMPU oligomers, with different concentrations, formed IPNs within the epoxy resins (diglycidyl ether of bisphenol A). The resultant IPN products were cured with diaminodiphenyl sulfone, diaminodiphenyl ether, and a Ciba–Geigy hardener under various curing conditions. Various mechanical properties, including the lap‐shear, peel, and impact strength, were evaluated. The results showed that 15 phr SiMPU led to better impact strength of epoxy resins than the others without the deterioration of the tensile properties. The impact strength increased continuously and reached a maximum value (five times greater than that of the virgin resin) at a critical modifier concentration (20 phr). The critical stress intensity factor reached 3.0 MPa m1/2 (it was only 0.95 MPa m1/2 for the virgin resin). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1497–1506, 2003
Reactor blending of polyethylene with ethyl‐bridged zirconocene catalyst and iron‐based diimine complex
Authors: Guo Cunyue , Ma Zhi , Zhang Mingge , Ke Yucai , Hu Youliang
Published: September 2003

Blends of polyethylene (PE) were produced in a single reactor using a combination of {[(2‐ArNC(Me))2C5H3N]FeCl2} [Ar2,6‐2CH3(C6H4)] and rac‐Et(Ind)2ZrCl2. The experimental results showed that the PEs obtained have a broad molecular weight distribution (MWD) and both the molecular weight and the MWD can be regulated through changing the mole ratio of the two active sites. In addition, the polymerization activities decreased with the increase of the Fe/Zr mole ratio whereas the crystallinity of the PE obtained exhibited a contrary trend, decreasing as the Fe/Zr mole ratio went up. The morphology of the blends also directly relates to the Fe/Zr mole ratio, and more iron content in the bimetallic catalysts system gives rise to compact PEs of high crystallinity. This reflects that the reactor blends are morphology controllable as well and can be easily applied to present processing techniques because of adjustable molecular weights and their distribution. Differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography, and scanning electron microscopy were employed to characterize the properties of the reactor blends of PEs. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1515–1518, 2003
Rice husk ash filled natural rubber. III. Role of metal oxides in kinetics of sulfur vulcanization
Authors: da Costa H. M. , Visconte L. L. Y. , Nunes R. C. R. , Furtado C. R. G.
Published: September 2003

In preceding investigations the overall rate and apparent activation energy for the vulcanization process were calculated for natural rubber compounds, assuming that vulcanization follows first‐order kinetics. It was observed that the addition of white rice husk ash (WRHA) increased the rate of crosslinking and lowered the apparent activation energy more profoundly than commercial fillers, precipitated silica (Zeosil‐175) and carbon black (N762), with a conventional vulcanization system. In this work, a specific model for the vulcanization process accelerated by N‐cyclohexylbenzothiazole sulfenamide was used to investigate the real role of WRHA in crosslink formation. Cure studies were carried out at 150°C, and the kinetics constants were evaluated. In relation to the other fillers, WRHA seems to develop catalytic activity, resulting in a positive effect on the specific rate of crosslink formation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1519–1531, 2003
Properties of extrusion cast sheets of blends of natural and aliphatic polyesters
Authors: Bhattacharya Mrinal , Mani Ramaswamy
Published: September 2003

Natural and synthetic polymers of various compositions were blended in a twin‐screw extruder. These blends were then sheeted into thin sheets with a coat hanger die attached to a single‐screw extruder. The natural content in the blend was varied between 5 and 50 wt %, and the mechanical and morphological properties of the blends were evaluated. At 50 wt % natural content, the tensile strength decreased to a third of that of the synthetic polymer. The use of a compatibilizer doubled the tensile strength for the 50 wt % natural content blend. The sheets displayed equal strengths in the machine and transverse direction. The tear strength decreased as the natural content increased, and the decrease was greater in the anhydride‐compatibilized blends than in the uncompatibilized blends. The blends displayed two distinct glass transitions, one for each component, indicating phase separation. The crystallinity of the blends decreased as the starch content increased. This result was confirmed by differential scanning calorimetry (DSC), which showed that the melting endotherm decreased as the starch content increased. Gel permeation chromatography (GPC) results showed that the peak position was at the same location irrespective of blend composition, indicating minimal degradation of starch moieties. The water absorption was diffusion controlled, with a sharp initial burst of water uptake. Scanning electron microscopy (SEM) showed melting of starch granules that formed a co‐continuous phase with the synthetic polyester. Increasing the natural content also increased the surface roughness of the sheets. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1545–1554, 2003
Influence of carboxylic acid additives on the flow behavior of molten thermoplastics
Authors: Ahn Sungtae , White James L.
Published: September 2003

Following the suggestions of the behavior of carboxylic acid lubricants between steel surfaces and the wide usage of such acids in polymer compounds, we have considered their influence as an additive in polymer melts. An experimental study of the influence of carboxylic acid additives in various thermoplastics in rheometers is described. Capillary and cone‐plate experiments are reported. A series of polymers of varying polarity, including polyethylene, poly(propylene), polystyrene, poly(methyl methacrylate), and polyamide‐12, are compared. Both aliphatic fatty acids and aromatic carboxylic acids were used as additives. The aliphatic fatty acids include propionic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid, and commercial stearic acid (mixture of tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid). The aromatic carboxylic acids include benzoic acid, p‐toluic acid, and 3‐phenylpropionic acid. The greatest effects were found with polyethylene and poly(propylene). Little or no effects were found with the other polymers. Aliphatic fatty acids were more effective than aromatic carboxylic acids. Mechanisms for this behavior are discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1555–1564, 2003
Melt‐intercalation nanocomposites with chlorinated polymers
Authors: Kim Younghoon , White James L.
Published: September 2003

Polyolefins and chlorine‐containing polymers were investigated to produce polymer nanocomposites. Natural and organic‐treated montmorillonite clays were melt compounded with the polymers. Organic‐treated montmorillonite clay dispersed well in polychloroprene, chlorinated‐polyethylene, polyvinyl chloride, chlorinated‐polyvinyl chloride, and polyvinylidenechloride polymers, and formed nanocomposites. They were not well dispersed in polyolefins that contain no chlorine. X‐ray diffraction and transmission electron microscopy techniques indicated the separation of montmorillonite layers and indicated the formation of polymer nanocomposites in chlorine‐containing polymers. Mechanical testing showed enhanced tensile strength and Young's modulus of chlorinated‐polymers/clay compounds, but not polyolefins/clay compounds. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1581–1588, 2003
Shape‐memory effects of radiation crosslinked poly(ϵ‐caprolactone)
Authors: Zhu G. , Liang G. , Xu Q. , Yu Q.
Published: September 2003

Poly(ϵ‐caprolactone) (PCL) with different molecular weight were crosslinked by γ‐radiation. The radiation crosslinking features were analyzed by Soxhlet extraction with toluene and the Charlesby–Pinner equation. The crosslinking degree is relative to molecular weight and radiation dose; the relation between sol fraction and dose follows the Charlesby–Pinner equation. All the samples were crystalline at room temperature, and the radiation crosslinking had a little effect on the crystallinity and the melting behavior of PCL. The shape‐memory results indicated that only those specimens that had a sufficiently high crosslinking degree (gel content is higher than about 10%) were able to show the typical shape‐memory effect, a large recoverable strain, and a high final recovery rate. The response temperature of the recovery effect (about 55°C) was related to the melting point of the samples. The PCL shape‐memory polymer was characterized by its low recovery temperature and large recovery deformation that resulted from the aliphatic polyester chain of PCL. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1589–1595, 2003
Living/controlled radical autopolymerization of styrene in the presence of CuCl2 and 2,2′‐bipyridine
Authors: Cheng Zhenping , Zhu Xiulin , Zhou Nianchen , Lu Jianmei
Published: September 2003

The bulk autopolymerization of styrene (St) was successfully conducted in the presence of CuCl2 and 2,2′‐bipyridine (bpy) at 110 and 130°C. We found that this polymerization was a living/controlled radical polymerization at a [St]0/[CuCl2]0/[bpy]0 ratio of 54:1:2.5. The resulting number‐average molecular weights linearly increased with conversion, and the polydispersity indices were very narrow (<1.5). The polymerization rate increased with temperature. Increasing the ratios (i.e., 129:1:2.5, 259:1:2.5, and 386:1:2.5) led to a decrease in the ability to control the autopolymerization of St, even uncontrolled polymerization (i.e., 643:1:2.5). The analysis of end groups by 1H‐NMR indicated that the spontaneous generation of radicals from St were generated by a Mayo‐type process, and this living/controlled radical polymerization might have underwent a reverse atom‐transfer radical polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1532–1538, 2003
Effect of the vulcanizing system on the mechanical properties of butyl rubber/ethylene propylene diene monomer–carbon black blends
Authors: Abd‐El Salam F. , Abd‐El Salam M. H. , Mostafa M. T. , Nagy M. R. , Mohamed M. I.
Published: September 2003

The effect of the vulcanizing system on the mechanical properties of butyl rubber/ethylene propylene diene monomer–general purpose furnace black–(GPF) blends was studied with static and dynamic mechanical measurements for these blends. The classical theory of elasticity was applied to show the mechanical behavior of the rubber–polymer blend and to calculate the degree of crosslinking. From the dynamic mechanical measurements, the elastic modulus, internal friction, and thermal diffusivity were calculated. The observed variations were explained in view of the role played by both the vulcanizing system and the reinforcing carbon black. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1539–1544, 2003
Effect of polydimethylsiloxane macrodiol molecular weight on properties and morphology of polyurethane and polyurethaneurea
Authors: Adhikari Raju , Gunatillake Pathiraja A. , Bown Mark
Published: September 2003

Two series of polyurethanes and polyurethaneureas were prepared using a two‐step bulk‐solution polymerization procedure. Each series consisted of three polymers based on three molecular weights of α,ω‐bis(6‐hydroxyethoxypropyl) polydimethylsiloxane (PDMS): 940, 1913, and 2955. The soft segment in all cases was an 80:20 mixture of PDMS and poly(hexamethylene oxide) (MW 700), and the hard segment was based on 4,4′‐methylenediphenyl diisocyanate and mixed chain extenders (40 wt %). In the polyurethane (PU) series the chain extender was a 60:40 (mol) mixture of BDO and 1,3‐bis(4‐hydroxybutyl)1,1,3,3‐tetramethyldisiloxane (BHTD), whereas in the polyurethaneurea (PUU) series it was a 60:40 (mol) mixture of BHTD and 1,2‐ethylenediamine. The polymerization was carried out by preparing a prepolymer using a bulk polymerization procedure followed by chain extension in a solution of N,N‐dimethylacetamide. Polymers were characterized by size‐exclusion chromatography, tensile testing, differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA). The number‐average molecular weights of the polymers in the PU series were in the range of 114,300–124,500, whereas they were in the 78,400–103,300 range for the PUU series. Polymers with good clarity and mechanical properties were obtained with PDMS‐940 and PDMS‐1913, but those obtained from PDMS‐2955, despite having good tensile strength, had a low percentage of elongation, high modulus, and poor clarity. DSC and DMTA results indicated that regardless of the PDMS molecular weight, the siloxane segments existed as a highly phase‐separated state. This poor compatibility was consistent with the low solubility of PDMS compared to that of the hard‐segment‐forming components. The polymers in the polyurethane series exhibited multiple melting endotherms, attributed to the melting of ordered domains from different hard segments. The combined heats of fusion were similar for the materials in the PU series. In contrast, the polymers in the PUU series showed a hard‐segment order that was significantly less defined, with the heat of fusion approximately a third to a half that of the materials in the polyurethane series. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1565–1573, 2003