bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of polyamide 6/6 synthesis carried out by interfacial polymerization on carbon fibre
Authors: Botelho Edson Cocchieri , Scherbakoff Natália , Rezende Mirabel Cerqueira 
Published: December 2002

AbstractPolyamide 6/6 synthesis via interfacial polycondensation of hexamethylenediamine and adipoyl chloride with simultaneous impregnation of carbon fibres was investigated. This experimental work was carried out to study the recovery of carbon fiber cables by polyamide 6/6 using six different concentrations of the monomer. Variation in the polyamide monomer concentration resulted in significant changes of chemical and morphological characteristics of the polyamide 6/6 and its composite with carbon fibre. Carbon fibre impregnation was evaluated by scanning electron microscopy (SEM), optical microscopy (OM) and thermogravimetric analysis (TGA), and the polyamide coating obtained in different concentrations was evaluated by differential scanning calorimetry (DSC), energy dispersive spectroscopy (EDS) analysis and TGA.© 2002 Society of Chemical Industry
Preparation and characterization of mesoporous materials based on silsesquioxane by block copolymer templating
Authors: Park Byeong‐Gyu , Jo Nam‐Ju , Cho Won‐Jei , Ha Chang‐Sik 
Published: December 2002

AbstractNanoporous materials were prepared by using silsesquioxane containing three alkoxy groups and a non‐hydrolysable organic moiety. The influences of pH and precursor ratios of silsesquioxane and tetraethyl orthosilicate (TEOS) on the preparation of organo‐modified periodic mesoporous materials were investigated. These materials were characterized using small angle X‐ray scattering, infrared spectroscopy and thermogravimetric analysis. A non‐ionic triblock copolymer was used as a structure‐directing agent to provide large pores with a high density of silanol groups. It was found that silsesquioxanes could form ordered nanoporous materials in the presence of TEOS by controlling the pH and the co‐precursors ratio, despite their structural irregularity.© 2002 Society of Chemical Industry
Distribution of space charges in luminescent conjugated polymers
Authors: Feller F , Geschke D , Monkman A P 
Published: December 2002

AbstractWe present investigations of the distribution of space charges in thin films of conjugated polymers. A thermal wave method (LIMM) has been used to resolve the depth profile of space charges and the distribution of the internal electric field in 3–4 µm films of poly(2,5‐pyridinediyl), the poly(p‐phenylenvinylene) derivative poly[2‐methoxy,5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylenvinylene] (MEH‐PPV) and polyfluorine (PFO). The results demonstrate that in conjugated polymers, space charges cannot only be created but can also be stored permanently. The electric field in the bulk of the film is significantly reduced because of the existence of two space charge layers: a narrow, positively charged layer at the front electrode, and a broader, negatively charged layer at about 500 nm. We assign the positive layer to the injection of positive charge carriers from the anode into near surface traps, and the second hetero‐charge layer to bulk charges that have been separated within the external electric field and accumulated in the trapping zone. The dynamics of the accumulation and poling of the space charge layers has been investigated by means of measurements of the temporal evolution and temperature dependence of the pyroelectric response.© 2002 Society of Chemical Industry
Novel vanadium‐containing polymers prepared from bis(arene)vanadium and acrylonitrile: third‐order non‐linear optical properties
Authors: Klapshina Larisa G , Semenov Vladimir V , Fominykh Zhanna Yu , Domrachev George A , Douglas William E , Antipov Oleg L , Kuzhelev Alexander S 
Published: December 2002

AbstractTreatment of (arene)2 V with acrylonitrile in the presence of a catalytic amount of tetracyanoethylene affords vanadium‐containing polyacrylonitrile. Thermolysis of the latter at 350 °C gives a naphthyridine‐type polymer containing 16% vanadium. Z‐scan measurements at 1064 nm for a solution of this thermolysed material in concentrated H2SO4 (c, 1 g l−1) gave a value of −1.8 × 10−13 cm2 W−1 (corresponding to Reχ(3) = −0.9 × 10−11 esu) for the electronic contribution to n2. The Z‐scan did not show any two‐photon absorption for beam intensities up to 0.3 GW cm−2. The vanadium‐containing polyacrylonitrile readily forms transparent films on casting from acetonitrile solution.© 2002 Society of Chemical Industry
Micropatterning of polyurethanes with lasers
Authors: Martelé Yves , Callewaert Kristof , Swennen Ives , Naessens Kris , Baets Roel , Van Speybroeck Veronique , Waroquier Michel , Van Aert Huub , Dierickx Patrick , Schacht Etienne 
Published: December 2002

AbstractThe micropatterning of a series new poly(carbonate‐urethanes) with IR and excimer lasers is discussed. A series of segmented polyurethanes consisting of a soft segment and a hard segment was prepared. The soft segment, a thermodegradable polycarbonate diol, degrades by asyn‐elimination at higher temperature. The hard segment was selected as to increase the sensitivity of the polymers for UV excimer laser ablation. The thermal and mechanical properties of the segmented polyurethanes (SPU) were investigated. By varying the building blocks in the polymer (soft and hard segments), the ablation properties were studied in terms of absorption coefficient and threshold value. Polymers with an aromatic chain‐extender and an diisocyanate showed the highest absorption coefficient at wavelengths of 248 and 193 nm. Irradiation of these polymers led to cavities with high dimensional quality, sharp edges and no accumulation of degradation products near the cavities (no debris formation). Ablation with an IR laser led to a decrease in film thickness of the polymer deposited on a substrate. This was investigated with FTIR/ATR analysis and atomic force microscopy. Debris formation was found near the cavities. The differentiation of polarity between the exposed and unexposed areas was not efficient enough to use them as a coating for printing plates.© 2002 Society of Chemical Industry
Characterization of an ABS‐modified epoxy system
Authors: Cano J , Torres A , Abad M J , Barral L , Díez F J , López J , Ramírez C 
Published: December 2002

AbstractIn this work an epoxy system containing a diglycidyl ether of bisphenol A (DGEBA) and 1,3‐bis(aminomethyl)cyclohexane (1,3‐BAC) is modified with poly(acrylonitrile‐co‐butadiene‐co‐styrene) (ABS). Using dynamic mechanical analysis the glass transition temperatures and the associated activation energies are determined in the neat epoxy and some blends. The presence of ABS produces a constant diminution of the glass transition temperatures and increases the activation energies. The brittle character of the neat epoxy and the blends, compared with the ductile character of ABS, is studied using an instrumented impact pendulum. The shape of force–time curves and energies and data dispersion of each composition are analyzed. By using scanning electron microscopy it is possible to see various zones of different roughness and to distinguish the regions of tension and compression of Charpy impact fractured surfaces. The presence of a two phase‐morphology in the epoxy‐ABS blends is also shown.© 2002 Society of Chemical Industry
Determination of some thermodynamical interaction parameters of polycaprolactone with some solvents by inverse gas chromatography
Authors: Saraç Ayfer , Türe Ahmet , Cankurtaran Özlem , Yılmaz Ferdane 
Published: December 2002

AbstractThe retention diagrams of polycaprolactone (PCL) were obtained between 70 and 140 °C with solvents such as n‐pentane, n‐hexane, n‐heptane, n‐octane, n‐nonane, n‐decane, isopropyl acetate, isobutyl acetate and tert‐butyl acetate by an inverse gas chromatography technique. Some thermodynamical parameters, namely the weight fraction activity coefficient of the solvent at infinite dilution, $\Omega_{1}^{\infty}$, the Flory–Huggins interaction parameter, $\chi_{12}^{\infty}$, at infinite dilution of solvent, the hard‐core interaction parameter, $\chi_{t}^{\infty}$, at infinite dilution of solute, and the effective exchange energy parameters, X
12 in the equation‐of‐state theory, were determined for these polymer–solvent systems. In addition, the partial molar heat of sorption, Δ
H
1, sorp, the partial molar heat of mixing, $\Delta \overline{H}_{1}^{\infty}$ of the solvents and the solubility parameter of the polymer, δ2, were determined for these systems. n‐Alkanes were particularly poor solvents but the esters studied were moderately good solvents for PCL. The solubility of the PCL did not change considerably with temperature in all the solvents studied. The values of interaction parameters were close to each other for PCL–ester systems studied. The solubility parameter of PCL, δ2, was found to be around 10 (cal cm−3)1/2 at room temperature and decreases linearly with temperature.© 2002 Society of Chemical Industry
Poly(lactic acid) nanocomposites with various organoclays. I. Thermomechanical properties, morphology, and gas permeability
Authors: Chang Jin‐Hae , An Yeong Uk , Sur Gil Soo 
Published: December 2002

AbstractThe thermomechanical properties, morphology, and gas permeability of hybrids prepared with three types of organoclays were compared in detail. Hexadecylamine–montmorillonite (C16–MMT), dodecyltrimethyl ammonium bromide–montmorillonite (DTA‐MMT), and Cloisite 25A were used as organoclays in the preparation of nanocomposites. From morphological studies using transmission electron microscopy, most clay layers were found to be dispersed homogeneously in the matrix polymer, although some clusters or agglomerated particles were also detected. The initial degradation temperature (at a 2% weight loss) of the poly(lactic acid) (PLA) hybrid films with C16–MMT and Cloisite 25A decreased linearly with an increasing amount of organoclay. For hybrid films, the tensile properties initially increased but then decreased with the introduction of more of the inorganic phase. The O2 permeability values for all the hybrids for clay loadings up to 10 wt % were less than half the corresponding values for pure PLA, regardless of the organoclay. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 94–103, 2003
Shear‐induced change of exfoliation and orientation in polypropylene/montmorillonite nanocomposites
Authors: Zhang Qin , Wang Yong , Fu Qiang 
Published: December 2002

AbstractFor the improved dispersion of montmorillonite (MMT) in a polypropylene (PP) matrix, PP/MMT nanocomposites prepared via direct melt intercalation were further subjected to oscillating stress achieved by dynamic packing injection molding. The shear‐induced morphological changes were investigated with an Instron machine, wide‐angle X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The original nanocomposites possessed a partly intercalated and partly exfoliated morphology. A transformation of the intercalated structure into an exfoliated structure occurred after shearing, and a more homogeneous dispersion of MMT in the PP matrix was obtained. However, the increase of the exfoliated structure was accompanied by the scarifying of the orientation of MMT layers along the shear direction. Some bended or curved MMT layers were found for the first time by TEM after shearing. However, the orientation of PP chains in the PP/MMT nanocomposites became very difficult under an external shear force; this indicated that the molecular motion of PP chains intercalated between MMT layers was highly confined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1–10, 2003
Correlation between melting behavior and ringed spherulites in poly(trimethylene terephthalate)
Authors: Wu Pi‐Ling , Woo E. M. 
Published: December 2002

AbstractThe lamellar types as revealed by the multiple melting peaks and possible mechanisms of ringed spherulites in poly(trimethylene terephthalate) (PTT) were analyzed with differential scanning calorimetry (DSC), optical microscopy, and scanning electron microscopy. Several interesting correlations were found. If PTT is melt‐crystallized in a certain temperature range, it shows multiple melting peaks and rings in PTT. Once rings are formed in the original melt‐crystallized PTT, they do not disappear but persist and become even more apparent upon postcrystallization annealing at higher temperatures. Furthermore, for PTT that is capable of exhibiting ringed spherulites, a temperature range exists where rings do not form. This behavior can be interpreted in relation with the demonstrated thermal behavior in PTT. Reorganization took place upon postcrystallization scanning or annealing to or at higher temperatures. A postulation was proposed and rigorously tested with evidence to correlate the ringed spherulites and melting behavior. Rings in PTT may be related to multiple lamellae in the spherulites. Consequently, if a temperature of crystallization is selected so that there is only one type of lamella in the spherulites, then there should be no rings. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 80–93, 2002
Conductivities and spectroscopic studies on hyperbranched polyurethane electrolytes
Authors: Hong Ling , Cui Yanjun , Wang Xinling , Tang Xiaozhen 
Published: December 2002

AbstractPolymer electrolytes were prepared with hyperbranched polyurethane, linear polyurethane as the host polymer, and lithium perchlorate (LiClO4) as the ion source. Fourier transform infrared spectra were used to analyze the bonding degree of Li+ with carbonyl and ether groups. Raman spectra were applied to analyze the aggregate degree of anion perchlorate ion (ClO). The spectra analysis indicated that the hyperbranched polyurethane could function as a “solvent” for the lithium salt. Also, the conductivity increased with increasing concentration of hyperbranched polymers in the host polymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 120–126, 2003
Effect of silane coupling agent on mechanical interfacial properties of glass fiber‐reinforced unsaturated polyester composites
Authors: Park Soo‐Jin , Jin Joong‐Seong 
Published: December 2002

AbstractA silane coupling agent, γ‐methacryloxypropyltrimethoxysilane, for the surface modification of glass fibers was varied between 0.1 and 0.8 wt %. To understand the role of interfacial adhesion of glass fiber/unsaturated polyester composites, contact angles of the silane‐treated glass fibers were measured by the wicking method on the basis of the modified Washburn equation with deionized water, diiodomethane, and ethylene glycol as testing liquids. As a result, silane‐treated glass fibers led to increased surface free energy, mainly because of their increased specific or polar component. The mechanical interfacial behaviors based on the interlaminar shear strength (ILSS) of the composites determined by short‐beam tests and the critical stress‐intensity factor (KIC) were also improved in the case of silane‐treated composites. The surface free energy and the mechanical interfacial properties especially showed the maximum value in the presence of 0.4 wt % silane coupling agent. It revealed that the increase of a specific component of the surface free energy or hydrogen bonding between the glass fibers and the coupling agents plays an important role in improving the degree of adhesion at interfaces in a composite system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 55–62, 2003
Inhibitory effect of chlorophyllin on the frequency of micronuclei induced by sodium nitrite in mice
Authors: Diaz‐Barriga Arceo S. , Hernández‐Ceruelos A. , Madrigal‐Bujaidar E. , Chamorro G. 
Published: December 2002

AbstractIn this report the potency of chlorophyllin (CHL) was evaluated to prevent two types of damage produced by nitrite in mice: the increase of micronucleated polychromatic erythrocytes (MNPE) and the bone marrow toxicity, measured as the index of polychromatic erythrocytes/normochromatic erythrocytes (PE/NE). The study was done in eight groups of male mice. The first three groups were administered orally for 4 days with sodium nitrite (10, 15 and 20 mg/kg), the daily administration with nitrite was followed by an intraperitoneal administration of CHL (4 mg/kg), three more groups were administered with the same amounts of nitrite, a seventh group of mice was treated with distilled water while another was treated with CHL (4 mg/kg). Our study produced two main results: (a) no bone marrow injury was induced by any of the tested chemicals, as indicated with the PE/NE index, and (b) CHL protected (as high as 44%) the MNPE produced in nitrite treated mice. Copyright © 2002 John Wiley & Sons, Ltd.
The effects of chard (Beta vulgaris L. var. cicla) extract on the kidney tissue, serum urea and Creatinine levels of diabetic rats
Authors: Yanardağ R. , Bolkent Ş. , Özsoy‐Saçan Ö. , Karabulut‐Bulan Ö. 
Published: December 2002

AbstractThe aim of this work was to investigate the effects of chard (Beta vulgaris L. var. cicla) extract on serum urea and creatinine concentrations and on kidney tissue in normal and streptozotocin‐diabetic rats. The extract was administered to rats at a dose of 2 g/kg every day for 28 days, 14 days after animals were made diabetic. On day 42, kidney tissue and blood samples were examined. Significant degenerative changes in kidney tissue of diabetic rats were observed, but in the group given chard extract, the morphology of kidney tissue was found to be nearly the same as the controls. Serum urea and creatinine levels significantly increased in the diabetic groups, but the chard extracts significantly reduced serum urea and creatinine levels. It is concluded that the extract of this plant may reduce serum urea and creatinine levels and confer a protective effect on the kidney of diabetic rats. Copyright © 2002 John Wiley & Sons, Ltd.
Perceived sources of occupational stress among Chinese off‐shore oil installation workers
Authors: Wong Tze‐Wai , Chen Wei‐Qing , Yu Tak‐Sun , Lin Yan‐Zu , Cooper Cary L. 
Published: December 2002

AbstractTo explore the perceived sources of occupational stress and their relative importance among Chinese off‐shore oil installation workers, we used a self‐administered questionnaire to study 51 stressors associated with off‐shore oil work among 561 Chinese workers in a state‐owned oil company. The mean scores of 51 individual stressors were calculated and ranked. Factor analysis was used to identify nine sources of stress which were also ranked according to their standard mean scores. The top four sources of stress were, in descending order of importance: ‘physical environment of the workplace’, ‘safety’, ‘interface between job and family/social life’ and ‘career and achievement’. The perceived sources of work stress in Chinese workers were different from those reported in earlier studies on UK off‐shore oil workers. These differences might be attributable to socio‐cultural factors or possibly, changes in perception to stress over time. A better understanding of the sources of stress is essential to promote the physical and mental health of off‐shore oil workers. More cross‐cultural comparative studies would be useful in elucidating the influence of socio‐cultural and environmental factors on stress perception. Copyright © 2002 John Wiley & Sons, Ltd.
Work and personal resources as long‐term predictors of well‐being
Authors: Kalimo Raija , Pahkin Krista , Mutanen Pertti 
Published: December 2002

AbstractThe aim of this longitudinal study was to recognize the work and personal factors that predict well‐being in the long run. The empirical analyses are based on sample data from a larger survey in 1986 and from the 10‐year follow‐up. Well‐being was determined in terms of psychological and physiological symptoms of strain. Discriminant analysis was used to identify the predictor variables which best characterize the differences between the extreme strain groups. Differences were observed in the strength of work and personal resources between workers with low and high strain, and in the role of these resources in the process of staying well at work. Strong personal resources, especially strong sense of coherence, seem to protect workers from strain and thus maintain well‐being. At work, factors related to social processes, i.e. social support and appreciation from colleagues and superiors, act as primary work‐related resources. In general, the personal resources were better discriminating factors than the work characteristics. Well‐being was found to be relatively stable. Copyright © 2002 John Wiley & Sons, Ltd.
Varieties of competitive parity
Authors: Powell Thomas C. 
Published: December 2002

AbstractStrategy research explains why some firms outperform others, typically using profit rates, shareholder returns, and other continuous dependent variables. This paper investigates winning as the dependent variable, as measured by distributions of annual industry leadership in profits and returns to investors. This shift in dependent variable introduces alternative null models of competitive parity, including skew distributions derived from the natural sciences, and empirical distributions from nonbusiness domains such as chess, politics, sports, and beauty pageants. An empirical study of 20‐year leadership in U.S. industries shows that performance distributions in business follow statistical power laws resembling those in natural phenomena, and closely resemble distributions found in sports, politics, and other nonbusiness domains. The results support a presumption of persistent performance advantages in business, but show that business outcomes are indistinguishable from outcomes in the wider scientific and competitive landscape, and are amenable to explanation using relatively simple heuristics. The paper shows how the choice of null model shapes firm performance explanations, and explores the consequences of a more inclusive approach to null models in strategy research. Copyright © 2002 John Wiley & Sons, Ltd.
Domestic violence during pregnancy in Rio de Janeiro, Brazil
Authors: Moraes C.L , Reichenheim M.E 
Published: December 2002

AbstractObjectives: To estimate the prevalence and risk groups of domestic violence during pregnancy among public health care users in Rio de Janeiro, Brazil. The study focuses on violence perpetrated by both women and partners. Method: 526 women giving birth at term in public maternities from March to October 2000 were randomly selected and interviewers used the Revised Conflict Tactics Scales (CTS2). Results: 33.8% [95% confidence interval (CI): 28.8–37.0%] of the respondents reported some form of physical violence and 16.5% (95% CI: 13.3–19.8%) referred to severe forms. A total of 78.3% (95% CI: 74.8–81.8%), 9.9% (95% CI: 7.5–12.7%) and 15.6% (95% CI: 12.6–18.9%) reported psychological aggression, sexual coercion and injuries, respectively. Physical violence mainly occurred among adolescent women with less schooling, who did not work outside the home, with fewer prenatal appointments, and with little social support. Families with more under‐five children, alcohol and drug abuse, and low socio‐economic status were also involved more frequently. Conclusion: High prevalence rates for various forms of domestic violence in Brazil suggest that the issue should be viewed as a major public health problem.