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  • Articles  (638)
  • Polymer and Materials Science  (638)
  • 1995-1999  (375)
  • 1980-1984  (263)
  • 1940-1944
  • 1995  (375)
  • 1983  (263)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of titanium surface roughness on proliferation, differentiation, and protein synthesis of human osteoblast-like cells (MG63) (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 389-401 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effect of surface roughness on osteoblast proliferation, differentiation, and protein synthesis was examined. Human osteoblast-like cells (MG63) were cultured on titanium (Ti) disks that had been prepared by one of five different treatment regimens. All disks were pretreated with hydrofluoric acid-nitric acid and washed (PT). PT disks were also: washed, and then electropolished (EP); fine sandblasted, etched with HCl and H2SO4, and washed (FA); coarse sandblasted, etched with HCl and H2SO4, and washed (CA); or Ti plasma-sprayed (TPS). Standard tissue culture plastic was used as a control. Surface topography and profile were evaluated by brightfield and darkfield microscopy, cold field emission scanning electron microscopy, and laser confocal microscopy, while chemical composition was mapped using energy dispersion X-ray analysis and elemental distribution determined using Auger electron spectroscopy. The effect of surface roughness on the cells was evaluated by measuring cell number, [3H]thymidine incorporation into DNA, alkaline phosphatase specific activity, [3H]uridine incorporation into RNA, [3H]proline incorporation into collagenase digestible protein (CDP) and noncollagenase-digestible protein (NCP), and [35S]sulfate incorporation into proteoglycan.Based on surface analysis, the five different Ti surfaces were ranked in order of smoothest to roughest: EP, PT, FA, CA, and TPS. A TiO2 layer was found on all surfaces that ranged in thickness from 100 Å in the smoothest group to 300 Å in the roughest. When compared to confluent cultures of cells on plastic, the number of cells was reduced on the TPS surfaces and increased on the EP surfaces, while the number of cells on the other surfaces was equivalent to plastic. [3H]Thymidine incorporation was inversely related to surface roughness. Alkaline phosphatase specific activity in isolated cells was found to decrease with increasing surface roughness, except for those cells cultured on CA. In contrast, enzyme activity in the cell layer was only decreased in cultures grown on FA- and TPS-treated surfaces. A direct correlation between surface roughness and RNA and CDP production was found. Surface roughness had no apparent effect on NCP production. Proteoglycan synthesis by the cells was inhibited on all the surfaces studied, with the largest inhibition observed in the CA and EP groups. These results demonstrate that surface roughness alters osteoblast proliferation, differentiation, and matrix production in vitro. The results also suggest that implant surface roughness may play a role in determining phenotypic expression of cells in vivo.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290314
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  • 2
    Electronic Resource
    Electronic Resource
    NMR relaxation study of thermal degradation in cured PMR polyimidesWork supported in part by NASA under grant NCC-3-164. (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1545-1557 
    Details
    ISSN: 0887-6266
    Keywords: NMR relaxation ; PMR polyimides ; thermal degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have studied cross-linking and thermal degradation of high-performance first-and second-generation PMR-15 polyimides, both thermoset and thermoplastic versions, by performing nonspectroscopic NMR solid echo T*2 relaxation measurements at temperatures up to 430°C using probes built for this purpose. We employ signal averaging and automated decomposition of the relaxation decays into two Gaussian components, the slower of which gradually appears above 300°C. Tracking the molecular mobility spectrum in terms of the relative intensity of the components and their relaxation times as temperature is cycled, we detect essentially no irreversible effects below the glass transition, measure permanent mobility reductions attributable to completion of cure, and find that exposure to temperatures above 380°C on the order of 1 h is required for substantial thermal degradation to occur. These results are closely supported by thermal and mechanical measurements on parallel specimens. Second-generation PMR resins appear to have higher microscopic rigidity and reduced viscous fraction at high temperatures. ©1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331012
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of reactive oxazolyl styrene-acrylonitrile copolymers (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 1673-1677 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of oxazoline-modified styrene-acrylonitrile (SAN) copolymers was prepared through the reaction of amino alcohols onto preformed SAN copolymers. Consequently, a variety of reactive copolymers were synthesized. The major focus of this study was to examine the influence of reaction conditions, i.e., the nature of the catalyst and amino alcohol structure, on reactivity. The ability to incorporate oxazoline groups onto preformed polymers is dependent on whether homogeneous reaction conditions are met. For example, the use of nonreactive solubilizing agents, i.e., cosolvent, is effective. However, optimum conditions are obtained when the catalyst is completely soluble in the reaction mixture containing the amino alcohol and SAN copolymer. With these restrictions, zinc stearate is quite effective. Our results show that controlled and reproducible levels of oxazoline can be incorporated (typically at a rate of 2 mol %/h) up to high levels. These results are general and therefore are applicable to a wide variety of nitrile-containing polymers. © 1995 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070561219
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  • 4
    Electronic Resource
    Electronic Resource
    Novel polymeric alcohols by controlled catalytic polymer functionalization (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 533-543 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Novel EPDM (ethylenepropylenediene monomer) and polybutadiene polyols can be synthesized by a two-step process of controlled hydroformylation and then reduction of the formyl groups to place a desired amount of pendant alcohol groups along the polymer chain. The degree of functionalization can be controlled by measuring gas uptake from a calibrated reservoir during hydroformylation. Hydroformylation can be performed in solution or under simulated melt-phase conditions using either HRh(CO)(PPh3)3 or Rh(acac) (CO)2 as catalysts. Reduction of the polyaldehyde by NaBH4 generates the polymeric alcohol without further reaction of the remaining double bonds. Polymer functionalization and further modifications were followed by H-NMR and FTIR. These unique hydrophobic polyols can be reacted further to produce other polymer systems. As an example, urethanes have been made with these polyols by reaction with diisocyanates. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070560502
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  • 5
    Electronic Resource
    Electronic Resource
    HTPB-based polyurethanes for inhibition of composite propellants (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 1151-1155 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyurethanes were synthesized by the reaction of hydroxyterminated polybutadiene (HTPB) and diisocyanates such as toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), and isophoron diisocyanate (IPDI). A number of fillers such as carbon black, kaolin, and antimony trioxide (Sb2O3) were used in these formulations. Mechanical and thermal stability of these polyurethanes were studied. Based on its properties, HTPB-MDI derived filled polyurethane was selected and evaluated as an inhibitor for a composite propellant. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070550801
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  • 6
    Electronic Resource
    Electronic Resource
    Fracture of porous polyethylene-bone composite (1983)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 17 (1983), S. 59-70 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Porous high-density polyethylene specimens were implanted in the femurs of mongrel canines. At the end of the residency period (3 or 6 months), the animals were sacrificed and the implants were retrieved. The work-of-fracture of the implant specimens was then determined using the technique of Tattersall and Tappin. The work required to fracture a specimen in three-point bending by controlled crack propagation through a triangular cross section was obtained directly from the load-deflection curve. The area of the resulting fracture surface was measured by macro-photographic techniques, and the work-of-fracture was calculated as work per unit area. The implants were subsequently sectioned and examined microradiographically to determine the extent of bone ingrowth. Bone specimens adjacent to the implants and porous high-density polyethylene controls (no ingrowth) were also tested to determine their work-of-fracture. The results showed that bone adjacent to the implant specimens had a higher work-of-fracture than normal medial, canine femoral bone and was not appreciably different from the composite. The work-of-fracture of porous high-density polyethylene was not significantly increased by an increase in bone infiltration, and this anomalous behavior was attributed to a degradation of the polyethylene during implant residence. Control studies supported this hypothesis.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820170106
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  • 7
    Electronic Resource
    Electronic Resource
    Theory of fire and fire processes (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 7 (1983), S. 79-88 
    Details
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: There are two major fire processes, an understanding of which is essential for effective fire safety design: (1) the conditions under which a combustible material may become involved in flaming combustion, and (2) the rate at which such a material, once involved, will provide an output of heat, smoke, toxic gases, etc., which can endanger people and property. The first process may be regarded as covering both ignition and spread of fire on materials; its complement is the way in which fire may become extinguished. It is necessary for such processes to bring in a characteristic of the basic combustion reaction which, directly or indirectly, expresses the reactivity of the combustion process. Thus pilot ignition is usually associated with an approximate surface fuel temperature. More basically, it is associated with a critical flow rate of volatiles and a critical heat loss from the flame, the latter being influenced by ambient oxygen and temperatures conditions as well as heat lost and gained by the fuel itself. The most important factor governing the production of dangerous product is the rate at which volatiles first (fuel controlled fires) and later air (air controlled fires) are fed into the flames. The reactivity is of less importance, although it may be one of the factors which control combustion efficiency. In general, the more efficient is the combustion the more heat is produced, but the less smoke and toxic gases are produced. Some of the main advances in the above areas are reviewed in this paper.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fam.810070206
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of ageing on the dielectric behaviour of silicone-EPDM blends (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 21-35 
    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: Dielektrische Messungen an Silikon, EPDM und einem Blend aus gleichen Gewichtsteilen beider Polymerer wurden im Frequenzbereich 1-105 Hz zwischen 25 und 200°C vor und nach Alterung in Wasser, Wasserdampf und Luft durchgeführt. Für das unpolare und nahezu verlustfreie EPDM werden niedrige Werte der Dielektrizitätskonstante und des Verlustfaktors gemessen. Die für EPDM beobachtete thermische Depolarisation ist bei in Luft gealtertem EPDM aufgrund von Dipolorientierung etwas ausgeprägter. Silikon wird in zwei Stufen polarisiert. Veränderungen der dielektrischen Eigenschaften und des spezifischen Gleichstromwiderstands nach Alterung belegen, daß Ladungsträger bei niedriger Temperatur und polare Silanolgruppen bei hoher Temperatur zur Polarisation beitragen. Die Eigenschaften des Blends hängen vom Alte-rungsmedium ab. Hydrothermische Alterung bewirkt eine qualitative Verbesserung des Dielektrikums Silikon durch Entfernung von Ladungsträgern und der Unterdrückung der Silikonhydrolyse durch EPDM. Durch Alterung des Blends in Luft nimmt dessen Polarisation zu, bedingt durch die Bildung von Ladungsträgern und Dipolen sowie die zusätzliche Grenzchicht. Aus Aktivierungsenergien wird gefolgert, daß die bei niedriger Temperatur stattfindende Polarisation mit der Beweglichkeit der Ladungsträger und der Orientierung von Seitengruppen zusammenhängt. rungsmedium ab. Hydrothermische Alterung bewirkt eine qualitative Verbesserung des Dielektrikums Silikon durch Entfernung von Ladungsträgern und der Unterdrückung der Silikonhydrolyse durch EPDM. Durch Alterung des Blends in Luft nimmt dessen Polarisation zu, bedingt durch die Bildung von Ladungsträgern und Dipolen sowie die zusätzliche Grenzchicht. Aus Aktivierungsenergien wird gefolgert, daß die bei niedriger Temperatur stattfindende Polarisation mit der Beweglichkeit der Ladungsträger und der Orientierung von Seitengruppen zusammenhängt.
    Notes: Dielectric measurements in the frequency (1-105 Hz) and temperature (25-200°C) domains have been carried out for silicone, EPDM, and their 50/50 (by weight) blend before and after ageing in water, steam and air. Low values of permittivity and loss tangent for EPDM reflect its non-polar and loss-free nature. Thermal depolarisation is also observed with EPDM and the air-aged specimen shows little rising trend due to dipole orientation. Silicone is found to be polarised in two steps. Changes in dielectric properties and DC resistivity on hydrothermal weathering and air ageing confirms that charge carriers contribute in the low-temperature step and polar silanol groups contribute in the high-temperature region. The properties of the 50:50 blend are very much sensitive to the medium of ageing. Hydrothermal ageing improves the quality of the dielectric of silicone due to removal of charge carriers and the suppression of silicone hydrolysis by EPDM. Ageing of the blend in air increases the polarisation to a very high level owing to the charge carriers, the additional interface and the dipoles formed during ageing. Activation energies suggest that the low temperature polarisation step is associated with charge carrier mobility and orientation of pendent groups.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052250103
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  • 9
    Electronic Resource
    Electronic Resource
    Conformational analysis of acetyl-L-phenylalanine p-acetyl and p-valeryl anilides (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1489-1498 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Empirical force-field calculations and ir and 1H-nmr spectra indicate that five-membered (C5) and seven-membered (C7eq) hydrogen-bonded rings are the preferred conformations of acetyl-L-Phe p-acetyl and p-valeryl anilides in nonpolar media. The C5/C7eq ratio was found to be dependent on the dryness of the solute and the solvent. This fact and the results from conformational-energy calculations suggest that a molecule of water participates in the stabilization of the C7eq conformation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220605
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  • 10
    Electronic Resource
    Electronic Resource
    Controlled release of macromolecules and pharmaceuticals from synthetic polypeptides based on glutamic acid (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 547-556 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Biocompatible, biodegradable copolymers of glutamic acid and ethyl glutamate were evaluated for their permeability to proteins ranging in molecular weight from 12,300 to 69,000. The results showed that the copolymers were sufficiently permeable that they could be used for the preparation of implantable, controlled-release systems capable of releasing therapeutic amounts of high-molecular-weight drugs.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220167
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