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  • Polymer and Materials Science  (150)
  • 1975-1979
  • 1970-1974  (150)
  • 1965-1969
  • 1950-1954
  • 1970  (150)
Collection
Publisher
Years
  • 1975-1979
  • 1970-1974  (150)
  • 1965-1969
  • 1950-1954
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 1361-1372 
    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: Gamma radiation-induced conductivity and permanent conductivity effects produced by high doses of 2 MeV electrons have been measured in two polyimidazopyrrolone polymers. Radiation-induced conductivity levels are small compared to those found in many common insulating polymers. Permanent increases in dark conductivity produced by accumulated doses of 5×109 rad at temperatures up to 300°C are not sufficient to inhibit ultraviolet-visible photoconductivity. High doses of 2 MeV electrons (5×109 rad) under the same temperature conditions produce no discernible effect on dielectric properties. Both radiation-induced conductivity and permanent dark conductivity increases were much smaller in one polymer (BTDA-DAB), suggesting the possibility of optimizing radiation resistance in this class of polymers by means of chemical structure variation. The radiolytic and thermal stability reported previously for this class of polymers has been generally confirmed, with particular reference to electrical properties.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 869-882 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystallization kinetics of a high molecular weight fraction of linear polyethylene was studied in dilute solutions of p-xylene, n-hexadecane, and decalin by dilatometric methods. For all solvents and temperatures, the experimental isotherms could be quantitatively described by the Avrami formulation for the complete transformation. This result is unique in the realm of polymer crystallization, since marked deviations from this theory are usually observed in more concentrated systems. The Avrami exponent is found to be n = 4 in all cases. The temperature coefficients of the rate constants are indicative of a nucleation controlled process. The data fit either a two-dimensional or three-dimensional nucleation mode, and a discrimination can not be made between these two cases. The interfacial free energies are found to be independent of the solvent medium. It is also shown that, irrespective of the type of nucleation control governing the kinetics, the same type governs the crystallite thickness of the lamella-like crystals that are formed.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 3049-3063 
    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: Rate of molecular bond rupture is successfully correlated by a Griffith-type energy balance to the strain energy release rate during ozone cracking of rubber. Rate of bond rupture is determined from electron paramagnetic resonance (EPR) measurements. The rate of strain energy release is determined from stress-elongation measurements during stress relaxation, creep, and cyclic loading tests. To compare with macroscopic crack studies, it was assumed that each ruptured bond created a given amount of fracture surface. Numerical agreement could be obtained by assuming each broken bond results in the production of an area of approximately 10-13 cm2. Using the surface energy density determined from stress relaxation tests in an energy balance gives surprisingly accurate predictions of expected behavior in creep and cyclic loading tests. There is a one-to-one correspondence between the rate of crack growth (bond rupture) and rate of energy release from strain and external work in all cases. It is proposed that such correlations give credence to a Griffith-type approach to environmental cracking which it did not have previously.
    Additional Material: 11 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 2905-2920 
    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: Cotton fiber was treated with aqueous trimethylbenzylammonium hydroxide (Triton B) at concentrations over the range 25%-40%. After complete removal of the swelling agent, the samples were evaluated for the extent of swelling, strength and elongation, birefringence, moisture regain, density, crystallinity, x-ray diffraction patterns, and microfibrillar morphology. Electron-microscopical examination and other evaluation of fine structure properties revealed that the nature of swelling is intercrystalline up to 30% concentration of Triton B, and intracrystalline beyond that. Although the swelling as measured by propanol-2 retention after treatment with 30% Triton B is about twice as much as that of the control, the original structure remains almost unchanged except for some gain in strength and elongation and increase in moisture regain. At 32% Triton B concentration and beyond, rapid decrystallization takes place, accompanied by a fall in birefringence, density, and crystallinity index. X-Ray analysis showed significant loss of lateral order and partial conversion of cellulose I to cellulose II at 35% and 40% Triton B concentrations. The results indicate that, used at the critical concentration of 30%, Triton B can be a useful swelling agent for cotton fibers as it opens up the fine structure of cellulose considerably without impairing any important physical properties.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 73-78 
    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 interpenetrating polymer networks were prepared containing PMMA and PEA as their two components. Corresponding telomer mixtures and random copolymers were also prepared for comparison purposes. The glass-rubber transition studies were made via shear modulus and dilatometric measurements. The results indicate one very broad transition for the IPN's rather than two transitions expected for incompatible polymer pairs. An interpretation based on the compatibility or near-compatibility of the PEA/PMMA pair is offered.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 4 (1970), S. 145-187 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The influences of the conditioning treatments, surface topography, and crystal structure of carbonaceous surfaces on their ability to sorb heparin and their in vivo compatibility with blood were investigated. The results of the sorption studies indicated that the adsorption of heparin on the surfaces of turbostratic and graphitic materials is not crystallographically selective and that the amount adsorbed on relatively smooth surfaces is near the amount expected for monolayer formation. Although the adsorption of heparin on relatively smooth carbon surfaces is not influenced by the presence of benzalkonium chloride, the sorption of heparin in porous carbons can be greatly increased by a pretreatment with benzalkonium chloride. This increase was found to be due to the formation and entrapment of the insoluble heparin-benzalkonium complex in the accessible porosity. Since the heparin sorptions in Dag-154 coatings were found to be enhanced by a pretreatment with benzalkonium chloride, it was inferred that these coatings contain accessible porosity and that their initial thromboresistance depends on the formation of the benzalkonium-heparin complex in pores. In vivo tests showed that polished and outgassed, impermeable isotropic carbons deposited at low temperatures were significantly thromboresistant without the exogenous application of heparin. There was no relationship between the amount of heparin sorbed on these materials and their compatibility with blood. Polishing, for example, which reduced heparin sorption, enhanced the thromboresistance of these carbons, and while chemisorption of oxygen markedly reduced their thromboresistance, it did not influence the amount of heparin that could be sorbed. Although the heparin-benzalkonium complex sorbed in a porous carbon conferred excellent thromoboresistance in a 2-hr test, the long-tern (14-day) compatibility was not as good as for carbon surfaces that were deposited at low temperatures and then polished and outgassed prior to implanting. In vivo tests of HTI carbon structures and annealed LTI carbons indicate that the blood compatibility of a turbostratic carbon is not significantly dependent on crystallite size, Le. Limited tests of surfaces that had a preponderance of c-faces oriented parallel to the blood-carbon interface at the surface suggest that orientations of this sort are better than others.
    Additional Material: 15 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 4 (1970), S. 275-277 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Autoclave sterilization of paper-wrapped stainless steel implants resulted in slight general surface corrosion and crystalline contamination. Such artifacts may produce microanodes which induce local tissue reactions, thereby lowering the pH and further activating the corrosion process. Implants sterilized in ethylene oxide or benzalkonium chloride did not show artifact corrosion or contamination. Mechanisms are presented to show the effects contaminants have upon both the corrosion behavior and the tissue reaction of implant materials.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 21 (1970), S. 613-629 
    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: Review of electrochemical methods of studying hydrogen embrittlement and stress corrosion crackingIn this review the authors presents the features common to both types of failure and the features by which the two types of failure are different from each other. In this context it is emphasized, that the hydrogen absorption - essential for embrittlement - can be regarded as a side reaction accompanying the particular overall reaction, and that the particular reaction conditioned and the structure of the metal play an important part. Different methods for investigating the hydrogen context and the state of the hydrogen (atomic, ionic, molecular) in the metal are described, and soo are methods for studying internal stresses due to hydrogen absorption. As to stress corrosion cracking it is shown that the processes involved are not a separate mechanical and a separate chemical one, but that the joint action of both is important. In this context it is shown, however, that this view can be considered to be established in th e case of austenitic steels only.
    Notes: Der Verfasser zeigt in diesem Übersichtsartikel die Faktoren, in denen die beiden Schadensarten übereinstimmen bzw. sich unterscheiden. Hierbei wird davon ausgegangen, daß die für die Versprödung entscheidende Wasserstoffaufnahme als eine die jeweilige Gesamtreaktion begleitende Nebenreaktion angesehen werden kann, wobei die jeweiligen Reaktionsbedingungen und das Gefüge des Metalls eine Rolle spielen. Die verschiedenen Methoden zur Untersuchung des Wasserstoffgehalts bzw. des Wasserstoffgehalts im Metall (atomar, als Ion, molekular) werden beschrieben, ebenso Methoden zur Untersuchung der durch Wasserstoff hervogerufenen inneren Spannungen. Hinsichtlich der Spannungsrißkorrosion wird gezeigt, daß es sich hierbei nicht um getrennte mechanische und chemische Vorgänge handelt, sondern daß das Zusammenwirken der beiden entscheidend ist. In diesem Zusammenhang wird allerdings darauf hingewiesen, das diese Ansicht nur für die austenitischen Stähle eindeutig festgestellt ist.
    Additional Material: 28 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 799-810 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular weights by osmometry (M̄n), light scattering (M̄w), and sedimentation-diffusion (MsD) were determined for selected fractions and unfractionated samples of hyaluronic acid in the molecular weight range 3 × 104-1.7 × 106. For the determination of MsD from the sedimentation coefficient s, a calibration procedure based on the data of Laurent, Ryan, and Pietruszkiewicz gave the following relations in 0.2M NaCl: log (s-1)0 = 14.681 - 0.413 log MsD and log D0 = -3.828 - 0.568 log MsD, where subscript, zero refers to zero concentration and D is the diffusion coefficient. The average Mandelkern-Flory parameter β in 0.2M NaCl is 3.0 × 106. Data for the intrinsic viscosity [η] may be fitted for M 〉 105 by [η] = K′Ma, where K′, a are in 0.2M NaCl, 0.0228, 0.816; in 0.5M NaCl, 0.0318, 0.777; in 0.1 M HCl, 0.0279, 0.763, respectively. Below M = 105, [η] appears to fall below the values calculated, possibly due to non-Gaussian behavior of short chains. The second virial coefficient A2 in 0.5M NaCl approaches the ideal Donnan value, decreasing slightly with increasing molecular weight. The friction parameter P is about 20% smaller than that of uncharged polymers of similar dimensions. The flexible coiling nature of this polymer is confirmed.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1105-1117 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oligo d(C-A) and oligo d(T-G) of known average lengths, prepared by a combination of chemical and enzymatic procedures, have been mixed in 0.02 M and 0.07 M Na+, and absorbance has been studied as a function of increasing temperature. The transitions have been analyzed for the temperature of maximum slope Tm, the breadth of the transition, the value of the slope at Tm, and the maximum hyperchromicity. Linear expressions have been found relating the inverse of the length in nucleotide units (n-1) of the shorter oligomer, irrespective of its identity, to Tm and also to the transition breadth. From a difference in slope between the Tm versus n-1 expressions for the two molarities, the entropy and enthalpy of melting have been calculated as a function of n-1.
    Additional Material: 7 Ill.
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