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  • Polymer and Materials Science  (309)
  • 1990-1994  (309)
  • 1980-1984
  • 1993  (309)
  • 1
    Electronic Resource
    Electronic Resource
    Metal ion concentrations in retrieved polyethylene total hip inserts and implications for artifactually high readings in tissue (1993)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 1349-1355 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Although there are many studies which document high metal ion concentrations in clinically retrieved tissues surrounding total joint replacements, most investigations have remained cautious in their interpretation due to the artifactual influences of metal particulate.The possible contribution of polyethylene wear debris to artifactually high periprosthetic metal ion concentration readings has not been previously considered. This study documents the potential role of polyethylene particulate contamination in causing artifactually high metal concentration readings in tissues.The data showed metal ion contamination in the polyethylene was progressive at each stage of exposure to metal: from bar stock preparation, to manufacturing, to in vivo ambulation. The manufacturing and machining processes showed a statistically significant (P ≤ .05) increase in metal ion concentrations in the nonarticulated acetabular inserts over bar stock.The results of this study demonstrate that periprosthetic tissue and synovial fluid metal ion concentration data must be interpreted with caution due to possible artifactual problems associated with metal ion contaminated polyethylene particulate. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820271102
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  • 2
    Electronic Resource
    Electronic Resource
    Points to be considered in thermogravimetry (1993)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 44 (1993), S. 345-350 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Bei der Thermogravimetrie zu berücksichtigende HinweiseKontinuierliche Thermogravimetrie ist eine verbreitete Methode, um Werkstoffe in korrosiven Gasen bei hohen Temperaturen zu prüfen und um Kinetik und Mechanismen der Hochtemperaturkorrosion aufzuklären. Hier werden Empfehlungen zur Durchführung thermogravimetrischer Tests zusammengestellt, Hinweise gegeben betreffend Probengröße und -form, Oberflächenpräparation, Reaktionsrohr, Start des Experiments, besonders empfindliche Messungen und Gasströmung und -regelung. Die Veröffentlichung ist als Grundlage und Startpunkt für zu entwickelnde Richtlinien für die Hochtemperaturkorrosionsforschung gedacht.
    Notes: Continuous thermogravimetry is a common method to test materials in gaseous corrosive environments at high temperatures and to elucidate kinetics and mechanisms of high temperature corrosion. Recommendations how to conduct thermogravimetric tests are collected here, points to be considered including sample size and form, surface preparation, reaction chamber, starting procedure, sensitive measurements, gas supply and dosing. This study is meant as a starting foundation for establishing guidelines in high temperature corrosion research.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19930440805
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  • 3
    Electronic Resource
    Electronic Resource
    Solid-State orientation studies on polypropylene disks, 2Part 2 cf.1.. Uniaxial compression with lubricated press platens (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 205 (1993), S. 177-184 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die molekulare Orientierung kreisförmiger Platten aus isotaktischem Polypropylen wurde anhand der optischen Doppelbrecung und des Infrarot-Dichroismus untersucht. Die Proben wurden zwischen vorgeheizten Pressplatten und unter Verwendung von Gleitmittel (Silikonöl) an der Pressplattenoberfläche einachsig komprimiert. Die Änderung der molekularen Anisotropie in den kristallinen Bereichen, bestimmt aus der optischen Deppelbrechung und dem Infrarot-Dichroismus, war vernachlässigbar klein über den Querschnitt der Scheiben. Der Grad der Anisotropie war relativ gering. Polfiguren, welche aus Weitwinkel-Röntgenstreuungsexperimenten bestimmt wurden, weisen auf das Entstehen einer planaren Orientierungstextur hin. Die Orientierung der Polymerketten in den kristallinen Bereichen lag hauptsächlich senkrecht zur Richtung der Kompression.
    Notes: The molecular orientation of isotactic polypropylene disks compressed uniaxially in the solid state using lubricated press platens was studied by measuring optical birefringence, infrared dichroism and wide-angle x-ray scattering. Differences in anisotropy obtained by optical birefringence and infrared dichroism were negligibly small throughout the disk at a low overall level of orientation. Pole figures obtained from WAXS measurements showed that the orientation texture developed during the deformation was essentially planar with polymer chains oriented perpendicularly to the compression direction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052050115
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  • 4
    Electronic Resource
    Electronic Resource
    GaAs/AlAs superlattice as a proposed new reference material for sputter depth profiling (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 1061-1066 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A GaAs/AlAs superlattice growth by metal-organic chemical vapour deposition is being proposed as the single crystalline multilayer reference material for sputter depth profiling. This material was characterized by transmission electron microscopy experiments, which showed that the interface between GaAs and AlAs is atomically flat. The preliminary depth profiling experiments were carried out by AES and SIMS.The AES experiments were performed using a Perkin-Elmer SAM 660 scanning Auger microprobe and the SIMS experiments were carried out using a VSW multitechnique XPS/SIMS surface analysis system.The AES and SIMS sputter depth profiling experiments proved that the depth resolution was found to be almost constant for each interface when an Ar+ beam was used for sputtering. Therefore the sputtering-induced roughness is very small for this material with Ar+ beam profiling, the depth resolution deteriorated as a function of depth, indicating oxygen ion beam-induced surface roughening.For both AES and SIMS, the depth resolution improved for ion beams with lower kinetic energy and more glancing angles of incidence.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740201306
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  • 5
    Electronic Resource
    Electronic Resource
    Photoemission study of an AuPdAu(111) multilayer grown by MBE (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 919-922 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An au/Pd/Au(111) multilayer system grown by molecular beam epitaxy has been studied by high-resolution x-ray photoelectron spectroscopy. An analysis of the dependence of the relative intensity of the Au and Pd core-level XPS lines on the take-off angle indicates that the thickness of the Pd sandwhich layer is ∼5 monolayers. The photoelectron spectra show the presence of more than one chemical environment for each element and suggest that the core-level photoelectron spectra of Pd atoms in the interfacial layers and the inner layers of the Pd sandwich are split by ∼0.6 eV. The photoelectron spectra of the valence band show that the Pd sandwich retains the high density of states at the Fermi energy that is characteristic of Pd metal.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740201107
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  • 6
    Electronic Resource
    Electronic Resource
    New developments in synthesis of star polymers with poly(ethylene oxide) arms (1993)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 44 (1993), S. 225-229 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of star molecules consisting of small polydivinylbenzene (DVB) cores carrying a number of hydrophilic poly(ethylene oxide) branches has been investigated. Two different methods are discussed:The “core-first” technique, in which living poly(DVB) cores are used to initiate the polymerization of oxirane. This method is flexible and efficient, but the samples obtained exhibit broad molecular weight distributions, arising from large fluctuations of the core functionalities (and core sizes). The same method has been applied successfully to the synthesis of star-block copolymers, in which each branch consists of a polystyrene (PS) block and a poly(ethylene oxide) (PEO) block.The “three-step” method (“In-Out”) involves the use of living polystyrene “seed-star” molecules as initiators for the polymerization of oxirane. The “seed-stars” themselves arise from a classical “arm-first” process. This method allows a better control of the functionality of the cores. The number of branches of either kind attached to a given core is equal. Hetero-star PS-PEO copolymers are obtained, but the length of the branches of either kind can be chosen at will within broad limits.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1993.010440503
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic vs. Steric effects of substituents on the intramolecular excimer fluorescence from dilute solutions of halogen-substituted polystyrenes (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 329-338 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Steady state fluorescence measurements in dilute solution have been performed for eight halogenated polystyrenes and for poly(2,5-dimethylstyrene). The monomers for halogenated polymers are o-X-styrene (X = F, Cl, Br), m-fluorostyrene, p-X-styrene, and p-chloro-α-methylstyrene. The position of the excimer band and the ratio of the intensities of the excimer and monomer fluorescence depend on the substitution. The results for poly(p-chloro-α-methylstyrene) and poly(2,5-dimethylstyrene) can be rationalized by a conformational analysis that examines the preferred geometries for face-to-face complexes by rings bonded to chain atoms i and i + 2. The results for the other polymers cannot be explained by a conformational analysis. They appear to arise from a combination of factors that alter the electronic properties of the chromophore.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940129
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  • 8
    Electronic Resource
    Electronic Resource
    Gamma-, photo-, and thermally-initiated oxidation of isotactic polypropyleneIssued as NRCC #34241. (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 715-722 
    Details
    ISSN: 0887-624X
    Keywords: polypropylene ; oxidation products ; gamma ; photoinitiation ; thermal ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The detailed oxidation products have been identified and compared from the γ-, photo-, and thermally-initiated oxidation of unstabilized polypropylene films. Products were identified and quantified by a combination of iodometric analysis and infrared spectroscopy. Spectral resolution was enhanced by derivatization reactions which allow the quantification of primary, secondary, and tertiary hydroperoxide and alcohol groups as well as more reliable analysis of carbonyl species. In contrast to polyethylene oxidation which yields predominantly ketone with lesser amounts of secondary hydroperoxide and carboxylic acid, polypropylene oxidizes to give predominantly tertiary hydroperoxide and lesser quantities of secondary hydroperoxide and ketone. In addition carboxylic acid groups are a minor product except at high degrees of thermal and photoinitiated oxidation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310316
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  • 9
    Electronic Resource
    Electronic Resource
    Investigation of the free radical polymerization of styrene in the presence of several 1,1-disubstituted ethylenes (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 901-908 
    Details
    ISSN: 0887-624X
    Keywords: styrene ; free radical ; addition-fragmentation chain transfer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variety of 1,1-disubstituted ethylenes, having an electron-withdrawing (capto) and an electron-donor (dative) substituent on the same carbon, were synthesized and added to styrene polymerizations. The dative substituents investigated were alkoxy or alkylcarbonate. After the addition of a polystyryl radical to a disubstituted ethylene, the resulting alkoxy or carbonate radicals could potentially fragment, resulting in chain termination and the formation of alkyl radicals. This process is called addition-fragmentation chain transfer (AFCT). The polymers produced during this study were examined for evidence of copolymerization and AFCT. The relative stability of the radicals generated by the fragmentation process appears to be the predominant factor controlling the ratio of copolymerization versus AFCT. © 1993 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310408
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  • 10
    Electronic Resource
    Electronic Resource
    PVD-beschichtete Tribosysteme bei reversierender Gleitbeanspruchung (1993)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 24 (1993), S. 160-167 
    Details
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: PVD-coated tribosystems at reciprocating slidingThe aim of the investigation is to increase the life time of machinery elements of steel, sliding under high contact pressure, by PVD-coating of one of the surfaces.The three-step tribological testprogram includes a fundamental test, a model test under real conditions and a suitability test with real parts. The coefficient of friction and wear depends on substrate material, deposition variance, coating structure and surrounding conditions.Hard coatings: They enlarge the life time of lubricated systems considerably (μ ≤ 0,1). Without lubrication the coefficient of friction is relatively high (μ ≥ 0,5), which results in a short life time.Coatings with low friction: Soft metals and chalchogenides on supporting hard coatings only reduce the friction for a short time. Metal carbon coatings yield the lowest coefficient of friction (μ = 0.2) and the greatest life time. In the range up to 1500 N/mm2 the pressure has a small influence on the life time. When the coated contact surface slides against an unmachined forged surface, the coating will be damaged after a short time due to local over oad at asperities.
    Notes: Das Ziel der Untersuchungen ist die Steigerung dcr Lebensdauer von unter relativ großen Pressungen gleitend beanspruchten Maschinenelementen aus Stahl durch PVD-Beschichtung eines der Kontaktpartner. Die tribologische Prüfung erfolgt dreistufig durch grundlagennahe Modellprüfung, beanspruchungsähnliche Modellversuche und Versuche am Bauteil (Steckkette) unter Praxisbedingungen. Substratwerkstoffe, Schichtsystem und Umgebungsbedingungen beeinflussen das Reibungs- und Verschleißverhalten wesentlich.Hartstoffschichten: Im geschmierten System verlängern sie die Lebensdauer erheblich (μ ≤ 0,1). Ohne Schmierung ist die Reibungszahl relativ groß (μ ≥ 0,5), was zum frühzeitigen Versagen des Tribosystems führt.Reibungsmindernde Schichten: Weichmetalle und Chalkogenide auf hartstoffbeschichteten Systemen vermindern die trockene Reibung nur kurzzeitig. Die kleinste Reibungszahl (μ = 0,2) und die größte Lebensdauer erbringen die Metall-Kohlenstoff-Schich-ten. Im Bereich bis zu 1500 N/mm2 hat die Pressung nur einen kleinen Einfluß auf die Lebensdauer. Bei Reibung gegen unbearbeitete, geschmiedete Steckkettenelemente wird die Schicht infolge lokaler Überbeanspruchung an Punktkontakten frühzeitig geschädigt.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19930240315
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