bluuebunny/crossref_metadata_2025_split huggingface dataset:
iPP/HDPE blends: Interactions at lower HDPE contents
Authors: Blom H. P. , Teh J. W. , Rudin A. 
Published: April 2003

AbstractMechanical and rheological properties of blends of polypropylene (PP) and linear polyethylene (PE) were studied, with particular attention to the effects of aging of such mixtures. These two olefin polymers are basically incompatible. In PP‐rich blends, addition of highdensity PE (HDPE) causes only a slight decrease in tensile properties and impact resistance of injection‐molded specimens. In all cases, annealed specimens have higher moduli and lower impact strength than as‐molded products. While none of these changes are very drastic, the addition of small amounts of HDPE was observed to result in a serious decrease of gate‐region impact resistance of thin‐walled moldings. Blends with 10–20% HDPE exhibited an unexpected interaction in tensile, thermal, and melt‐flow properties as well as in crystallization behavior. © 1995 John Wiley & Sons, Inc.
Studies of rigid poly(vinyl chloride) (PVC) compounds. I. Morphological characteristics of poly(vinyl chloride)/chlorinated polyethylene (PVC/CPE) blends
Authors: Chen C. H. , Wesson R. D. , Collier J. R. , Lo Y. W. 
Published: April 2003

AbstractChlorinated polyethylene (CPE) is a commonly used impact modifier of poly(vinyl chloride) (PVC). The major goal of this research was to understand the fundamental morphological aspects of PVC/CPE blends. Scanning electron microscopy (SEM) was used to image the surface structure of these blends, and both transmission electron microscopy (TEM) and scanning‐transmission electron microscopy (S‐TEM) were used to image the morphological boundaries of the blends. TEM imaging distinguishes the boundaries between PVC and CPE more clearly or better than does S‐TEM, but it is time‐consuming. However, some CPE particles are not observed in TEM because of inefficient staining. S‐TEM imaging is much faster and does not depend on staining for the imaging of the CPE phase. © 1995 John Wiley & Sons, Inc.
Studies on the formation of novel copolyesters containing naphthalene and aralkyloxy structures
Authors: Sun Y.‐M. , Wang C.‐S. 
Published: April 2003

AbstractCopolyesters containing naphthalene structure were synthesized from bis(hydroxyethyl)naphthalate (BHEN) and various aralkyloxy diols. The starting bis(4‐(2‐hydroxyethoxy)aryl) compounds were derived from a nucleophilic substitution of various bisphenols with ethylene carbonate in the presence of potassium iodide (KI). Copolyesters having intrinsic viscosities of 0.50 to 0.60 dL/g were obtained by melt polycondensation in the presence of metallic catalysts. The effects of reaction temperature and time on the formation of copolyesters were investigated in order to obtain an optimum condition for copolyester manufacturing. The optimal reaction temperature and time were found to be 290 to 310°C and 90 to 120 min, respectively. Most of these copolyesters have better solubilities than polyethylene naphthalate (PEN) in aprotic solvents such as N‐methyl‐2‐pyrrolidone or m‐cresol. The thermal properties of the copolyesters were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Glass transition temperatures of these copolyesters were in the range of 90 to 141°C, and 10% weight loss values in nitrogen were all above 460°C. © 1995 John Wiley & Sons, Inc.
Influence of poly(arylether sulfone) molecular weight distribution on measures of global thermal stability
Authors: Broadbelt Linda J. , Klein Michael T. , Dean Barry D. , Andrews Stephen M. 
Published: April 2003

AbstractThe dependence of the thermal stability of high‐performance poly(arylether sulfones) (PAES) on the initial molecular weight distribution and backbone structure was assessed experimentally and through computer simulation. Reaction of PAES polymers resulted in the formation of an insoluble gel fraction and significant changes in weight and number average molecular weights of the sol fraction. A PAES with alternating ether and sulfone linkages formed a larger fraction of gel at a given reaction time than a PAES with the hydroquinone moiety. For a given chemical composition, more rapid molecular weight changes and gel fraction formation were observed for the polymer with the higher value of the initial weight average molecular weight. The growth of molecular weight was also faster for the polymer with the broader initial distribution. The simultaneous increase in Mw and decrease in Mn suggested the occurrence of two types of overall reactions: scission and addition. Simulation of these reactions using Monte Carlo kinetics allowed estimation of the range of probability for bond scission, R, of 0.5 < R < 0.8 capable of accounting for the observed experimental behavior. The dependence of the simulated molecular weight changes on the initial molecular weight distribution agreed qualitatively with the experimental trends. © 1995 John Wiley & Sons, Inc.
Crystallization of very low density copolymers of ethylene with α‐olefins
Authors: Minick J. , Moet A. , Hiltner A. , Baer E. , Chum S. P. 
Published: April 2003

AbstractDifferential scanning calorimetry (DSC) was used to analyze the crystal distribution in homogeneous ethylene–octene copolymers polymerized by the constrained geometry catalyst technology (CGCT). To minimize ambiguities from thermal history effects, copolymers were isothermally annealed at temperatures within the melting range. The cumulative crystallinity was related to the crystal distribution by the Gibbs–Thomson equation. The results provided a clear distinction between Type I copolymers (density less than 0.89 g/cc) and Type II copolymers (densities between 0.89 and 0.91 g/cc). The former had a singlecrystal population that was identified with the bundled crystals seen in transmission electron micrographs. In comparison, the latter had two crystal populations that correlated with lamellar crystals and bundled crystals. © 1995 John Wiley & Sons, Inc.
Melt polycondensation of poly(ethylene terephthalate) in a rotating disk reactor
Authors: Cheong Seong Ill , Choi Kyu Yong 
Published: April 2003

AbstractA multicompartment model is proposed for a semibatch melt polycondensation of poly(ethylene terephthalate) in a rotating disk polymerization reactor and compared with laboratory experimental data. The reactor is a horizontal cylindrical vessel with a horizontal shaft on which multiple disks are mounted. The reactor is assumed to comprise N equal sized compartments and each compartment consists of a film phase on the rotating disk and a bulk phase in which disks are partially immersed. The effects of disk rotating speed, number of disks, reaction temperature, and pressure were investigated. It was observed that ethylene glycol is predominantly removed from thin polymer layers on the rotating disks and the enhanced interfacial area exerted by ethylene glycol bubbles accounts for about 30–50% of the total available interfacial mass transfer area. Although the rate of polymerization increases as more disks are used, the maximum number of disks in a reactor must be determined properly in order to prevent the formation of thick polymer films that result in a reduced specific interfacial area and reduced polymerization efficiency. At a fixed reaction pressure, the equilibrium conversion is reached but the rate of reaction can be further increased by increasing the reaction temperature. The results of the proposed multicompartment model are also compared with those predicted by a simple one‐parameter model. © 1995 John Wiley & Sons, Inc.
Membranes based on poly(styrene‐N‐phenylmaleimide)/poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends
Authors: Lokaj J. , Sikora A. , Pientka Z. , Bleha M. 
Published: April 2003

AbstractBlend membranes were prepared by casting chloroform solutions of mixtures of styrene‐N‐phenylmaleimide copolymer containing ca. 10 mol % imide units with poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO), and their phase behavior was evaluated. At a content of 20% PPO, the membranes were homogeneous; those having 40 or more % PPO exhibited phase separation. Membranes made of the parent polymers and their blends were tested in the pervaporation of aqueous ethanol solutions; permeabilities to oxygen, nitrogen, and carbon dioxide were also determined. The pervaporation characteristics and gas transport properties are discussed considering the interactions of polymer chains and the phase structure of the membranes. © 1995 John Wiley & Sons, Inc.
Practical aspects of polymerization of D,L‐Lactide initiated with tetraphenyltin
Authors: Mehta Sanjay , Raghuvanshi R. S. , Misra A. , Ganga S. , Talwar G. P. 
Published: April 2003

AbstractMelt polymerization conditions for D,L‐Lactide initiated with tetraphenyltin were studied with regard to polymer molecular weight. The combined effect of time and temperature on polymer molecular weight and degree of conversion of D,L‐Lactide is described. Polymerization at constant initiator concentrations resulted in a narrow scattering of reproducible molecular weight values. The presence of air/moisture and other impurities during the melt polymerization most likely have a deterimental effect on molecular weight. After a short induction period the rather slow polymerization of D,L‐Lactide resulted in a maximal molecular weight followed by an almost constant value of molecular weight. © 1995 John Wiley & Sons, Inc.
Pervaporation separation of binary organic–aqueous liquid mixtures using crosslinked PVA membranes. III. Ethanol–water mixtures
Authors: Lee Kew‐Ho , Kim Hae‐Kyung , Rhim Ji‐Won 
Published: April 2003

AbstractThe application of the pervaporation process in biotechnology is rapidly growing. A two stage pervaporation process could be applied to the downstream processing of ethanol fermentation. In this paper, the second stage process—a water‐selective process—was investigated in detail using the crosslinked poly(vinyl alcohol) membranes with the low molecular weight of poly(acrylic acid) as the crosslinking agent. The ratio of poly(vinyl alcohol) and poly(acrylic acid) in the membrane was 90/10, 85/15, and 80/20 by weight. The prepared membranes were tested to separate the various compositions of the water–ethanol mixtures, specially 50/50 solution at 60°C and 30/70, 20/80, 10/90, and 4.4/95.6 solutions at 60, 70, and 75°C. For water: ethanol = 50 : 50 solution, the separation factor αw/e = 260 at 75°C was obtained by using a PVA/PAA = 80/20 membrane. The permeation rate and the separation factor at the azeotropic point of a water–ethanol mixture showed 30 g/m2/h and 5800 at 75°C, respectively, when a PVA/PAA = 80/20 membranes was used. © 1995 John Wiley & Sons, Inc.
Effect of simulated low earth orbit radiation on polyimides (UV degradation study)
Authors: Hill David J. T. , Rasoul Firas A. , Forsythe John S. , O'Donnell James H. , Pomery Peter J. , George Graeme A. , Young Philip R. , Connell John W. 
Published: April 2003

AbstractUV degradation of polyimide films in air and vacuum were studied using UV‐visible, ESR, FTIR, and XPS spectroscopies. The UV‐visible spectra of polyimide films showed a blue shift in the absorption compared to Kapton. This behavior was attributed to the presence of bulky groups and kinks along the polymer chains which disrupt the formation of a charge‐transfer complex. The UV‐visible spectra showed also that UV irradiation of polyimides result extensively in surface degradation, leaving the bulk of the polymer intact. ESR spectra of polyimides irradiated in vacuum revealed the formation of stable carbon‐centered radicals which give a singlet ESR spectrum, while polyimides irradiated in air produced an asymmetric signal shifted to a lower magnetic field, with a higher g value and line width. This signal was attributed to oxygen‐centered radicals of peroxy and/or alkoxy type. The rate of radical formation in air was twofold higher than for vacuum irradiation and reached a plateau after a short time. This suggests a continuous depletion of radicals on the surface via an ablative degradation process. FTIR, XPS, and weight loss studies supported this postulate. An XPS study of the surface indicated a substantial increase in the surface oxidation after irradiation in air. The sharp increase in the CO binding energy peak relative to the CC peak was believed to be associated with an aromatic ring‐opening reaction. © 1995 John Wiley & Sons, Inc.
Viscoelastic properties and coating performance of water‐soluble acrylic copolymers crosslinked with melamine resin
Authors: Fukuda Tadanori 
Published: April 2003

AbstractAcrylic copolymers with different amounts of carboxyl and hydroxyl groups for obtaining practical performance of melamine‐cured acrylic coatings was investigated. Property testing results indicated that glass transition temperature (Tg) and shear modulus increased, and molecular weight between crosslinks (Mc) decreased with the increase of hydroxyl and carboxyl number in the acrylic copolymers. The degree of crosslinks influenced the resistance to solvent and chemicals at a lower baking temperature. Compared with acrylic acid, itaconic acid as a carboxyl monomer was more effective in inducing a lower baking schedule. The water‐soluble acrylic copolymer, which is neutralized with triethylamine, consists of 20 wt % methylmethacrylate, 55 wt % buthylacrylate, 15 wt % hydroxyethyl methacrylate, and 10 wt % itaconic acid. The copolymer showed higher crosslinks when cured with methoxymethyl melamine formaldehyde resin under a relatively lower baking schedule at 135°C for 30 min. It also has excellent solvent and chemical resistance. This coating film has a Tg value of 39°C, modulus of 2 × 108 dyne/cm2 in the rubbery state, and Mc value of 464. Also the acrylic copolymer films with Mc < 900 have good properties for solvent, acid, and alkali resistance. © 1995 John Wiley & Sons, Inc.
Studies on swelling of cotton fibers in alkali metal hydroxides. IV. Influence of initial fiber properties and variations in fine structure on tensile behavior
Authors: Sreenivasan S. , Iyer P. Bhama , Patel G. S. 
Published: April 2003

AbstractNineteen varieties of cotton, covering a wide range of fiber properties like maturity, fineness, and strength uniformity ratio were swollen in 5N KOH and NaOH at room temperature (30 ± 1°C). Tensile and fine structural properties of the resultant samples were measured and their relationship with initial fiber properties was examined. A comparative evaluation of fiber properties of KOH swollen fibers with those swollen in NaOH revealed that, irrespective of variety, fibers swollen in the former reagent retain higher tenacity. It was further noted that fine structural parameters like crystallite orientation and amorphous content which influence tensile properties become modified differently while swelling in the two reagents. While changes in crystallite orientation were found to be less drastic during KOH swelling, unlike in NaOH, the reverse was found to be true with crystalline content. These changes in fine structure could more or less explain the variation in tensile properties of fibers swollen in these two reagents. © 1995 John Wiley & Sons, Inc.
Polymerization of 2‐dibutylamino‐1,3,5‐triazine‐4,6‐dithiol on wire during friction process
Authors: Mori Kunio , Ibashi Wataru , Hirahara Hidetoshi , Oishi Yoshiyuki , Katayama Masanari 
Published: April 2003

Abstract2‐Dibutylamino‐1,3,5‐triazine‐4,6‐dithiol (DB) and a mixture of DB and triallylisocyanurate (TAIC) were used as a lubricant during steel wire drawing due to a dry process. DB gave a polymer film with 180 nm in thickness to wire surfaces during the wire drawing. The polymer film had a disulfide structure on the backbone and contained a small amount of DB monomer and olygomer. Molecular weight and polymer weight increased with the drawing rate. The mixture of DB and TAIC gave mainly a three‐dimensional polymer film with 225 nm in thickness to wire surfaces during drawing. The polymer film insoluble in THF had mono and disulfide structures and contained a small amount of linear polymer, DB, and TAIC. Such tribological polymerizations are estimated as follows: DB produces dithiyl radicals on a nascent surface formed during drawing and in the presence of oxygen and heat. The dithiyl radicals were polymerized by coupling with each other to give disulfide bonds or added to allyl groups in TAIC to give monosulfide bonds. It is concluded that this technique should be possible to use for unifying metal processing and surface treatment. © 1995 John Wiley & Sons, Inc.
Reduced number of intrinsic pulmonary nitrergic neurons in Fawn‐Hooded rats as compared to control rat strains
Authors: Van Genechten Jeroen , Brouns Inge , Scheuermann Dietrich W. , Timmermans Jean‐Pierre , Adriaensen Dirk 
Published: April 2003

AbstractThe Fawn‐Hooded rat (FHR) strain reveals a congenital predisposition to primary (idiopathic) pulmonary hypertension (PPH), and can therefore be regarded as an animal model in which to study possible mechanisms underlying an inherited susceptibility to pulmonary hypertension. Pulmonary hypertension can be induced in FHRs after a short exposure to mild hypoxia, presumably because of an altered peripheral oxygen sensitivity. Given the presence of pulmonary nitrergic neurons in rat lungs, the observed link between airway hypoxia and the expression of pulmonary neuronal nitric oxide synthase (nNOS), and the fact that nNOS appears to be involved in peripheral chemoreceptor sensitivity, we examined the intrinsic pulmonary nitrergic innervation in the FHR. In the present study the number of intrapulmonary nitrergic nerve cell bodies, detected by NADPH diaphorase (NADPHd) histochemistry, was quantified in the FHR and three control rat strains. Compared to the control rat strains, the FHR lungs revealed a highly significantly lower number of intrinsic nitrergic neurons, while no apparent differences were found in the number of enteric nitrergic neurons in the esophagus. In conclusion, the possible links between neuronal NO, hypersensitivity to airway hypoxia, and the development of PPH clearly deserve further investigation. Anat Rec Part A 272A:446–453, 2003. © 2003 Wiley‐Liss, Inc.
Hormone replacement therapy and cancer risk: A systematic analysis from a network of case‐control studies
Authors: Fernandez Esteve , Gallus Silvano , Bosetti Cristina , Franceschi Silvia , Negri Eva , La Vecchia Carlo 
Published: April 2003

AbstractTo provide comprehensive and quantitative information on the benefits and risks of hormone replacement therapy (HRT) on several cancer sites, we systematically examined the relation between HRT use and the risk of various cancers in women aged 45–79 by using data from a framework of case‐control studies conducted in Italy between 1983 and 1999. The overall data set included the following incident, histologically confirmed neoplasms: oral cavity, pharynx, larynx and esophagus (n = 253), stomach (n = 258), colon (n = 886), rectum (n = 488), liver (n = 105), gallbladder (n = 31), pancreas (n = 122), breast (n = 4,713), endometrium (n = 704), ovary (n = 1,614), urinary bladder (n = 106), kidney (n = 102), thyroid (n = 65), Hodgkin's disease (n = 26), non‐Hodgkin's lymphomas (n = 145), multiple myeloma (n = 65) and sarcomas (n = 78). The control group comprised 6,976 women aged 45–79 years, admitted for a wide spectrum of acute, nonneoplastic conditions. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) for use of HRT were derived from multiple logistic regression equations. There was an inverse association between ever use of HRT and colon (OR = 0.7), rectum (OR = 0.5) and liver cancer (OR = 0.2), with a consistent pattern of protection for duration of use. An excess risk was found for gallbladder (OR = 3.2), breast (OR = 1.1), endometrial (OR = 3.0) and urinary bladder cancer (OR = 2.0). These data from a southern European population add some useful information on the risk‐benefit assessment of HRT among postmenopausal women. © 2003 Wiley‐Liss, Inc.
Über die konzentrationsabhängigkeit der viskositätszahl bei linearen und verzweigten makropolymeren. XII. Mitteilung über polyester
Authors: von Batzer Hans , Von Weissenberger Unter Mitarbeit G. , Lung M. , Lang H. 
Published: April 2003

AbstractLineare Polyester ergeben im untersuchten Bereich eine lineare Konzentrationsabhängigkeit von ηsp/c; bei verzweigten Polyestern zeigt sich eine andere Beziehung. Eine den verzweigten Polyestern analoge Konzentrationsabhängigkeit der Viskositätszahl ergab ein als verzweigt angesehenes Polyvinylchlorid, während ein anderes Muster dieses Polymerisates der Beziehung von Schulz‐Blaschke entspricht.
Über Perlpolymerisation
Authors: Trommsdorff von E. 
Published: April 2003

AbstractVerteilt man in Wasser schwerlösliche Monomere durch mechanische Bewegung in Wasser, so bilden sich Tröpfchen. Durch Polymerisation der in Bewegung gehaltenen Tröpfechen kann man Polymerisatkugeln erhalten. Dieser Vorgang liegt der Perl‐ oder Suspensionspolymerisation zugrunde, die eine nicht geringe technische Bedeutung besitzt, bisher aber wissenschaftlich wenig bearbeitet ist. Reaktionskinetisch unterscheidet sich die Perlpolymerisation nicht von der Polymerisation des unverdünnten Monomeren. Sie ist zutreffend als „wassergekühlte Blockpolymerisation”︁ gekennzeichnet worden. Hinsichtlich des Reaktionsablaufs und der Art der Reaktionsprodukte unterscheidet sie sich von anderen in heterogener Phase in Wasser ablauenden Polymerisationsmethoden, nämlich der Emulsions‐, Dispersions‐ und Fällungspolymerisation. Die wäßrige Phase bei der Perlpolymerisation enthält Suspensionsstabilisatoren oder Verteilungsmittel. Diese haben die Aufgabe, das Ineinanderfließen der polymerisierenden Masse und das Verkleben der Polymerisatkügelchen zu verhindern. Die wichtigsten Verteilungsmittel sind: Wasserlösliche makromolekulare Verbindungen wie Gelatine, wasserlösliche Cellulose‐Derivate, Polyvinylalkohol, polyacrylsaure Salze sowie anorganische Pulver oder Niederschläge wie Talkum, Magnesiumcarbonat, Betonit, Calciumphosphat.Die Verteiler dürfen die Grenzflächenspannung zwischen Wasser und Monomerem nicht stark heruntersetzen. Die Stabilität der Tröpfchen ist bei höherer Grenzflächenspannung groß, so daß sie sich ähnlich wie elastische Bälle verhalten.Bei Erniedrigung der Grenzflächenspannung kommt es leicht zu Deformationen sowie einem Zusammenfließen der Tröpfchen. Die Wirkung der Suspensionsstabilisatoren beruht weiter auf der Stabilisierung der Wasserhaut zwischen den Tröpfchen, die sich nicht bis zur Berührung nähern können.Vorstellungen dieser Art werden zur Verständlichmachung der Verteilerwirkung entwickelt und die bei der Perpolymerisation auftretenden Fehlermöglichkeiten diskutiert.
Action des solutions de soude sur les fibres de cellulose – equilibres de fixation de la soude – mercerisation
Authors: Chédin Par Jean , Marsaudon Andrée 
Published: April 2003

AbstractOn a étudié par voie chimique, en utilisant une méthode aussi rigoureuse que possible, la fixation de la soude sur la cellulose. On a aussi déterminé la quantité de soude fixée, et son hydratation, en fonction de la concentration des solutions sodiques. Une théorie d'ensemble a été ainsi élaborée, faisant intervenir les «hydrates» probables de la soude en solution, par l'intermédiaire d'équations d'équilibres. L'accessibilité des fibres natives dépend de la concentration des solutions de soude, et ce fait est aisément interprétable, qualitativement. Les fibres prélablement mercerisées, au contraire, semblent accessibles entièrement pour toutes les concentrations. Les conclusions rejoignent celles qui avaient été tirées à la suite d'un travail antérieur concernant l'action mercerisante des solutions aqueuses d'acide nitrique – un peu de cellulose ajoutée dans ces solutions (NO3H ou NaOH) joue un rôle analogue à un peu d'eau ajoutée (1OH actif par maillon C6), et les hydrates de soude ou d'acide nitrique, peuvent se constituer avec l'eau du mélange ou avec les OH cellulosiques.La mercerisation de la cellulose est un phénomène analogue à l'interaction des hauts polymères polaires et de leurs solvants, plastifiants.