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  • Chemistry  (17)
  • Nickel coated graphite  (1)
  • Dynamic properties
  • 1990-1994  (18)
  • 11
    Electronic Resource
    Electronic Resource
    Poly(3-hydroxybutyrate)-co-(3-hydroxyvalerate)/Poly-L-lactide blends: Thermal and mechanical properties (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 1525-1535 
    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: Blends of poly(3-hydroxybutyrate)-poly(3-hydroxyvalerate) (PHBV) and poly(L-lactides) (PLLA) have been prepared by solvent casting. Compatibility, thermal behavior, morphology, and mechanical properties of systems with various compositions were studied using differential scanning calorimetry (DSC), dynamic mechanical measurement, tensile tests, scanning electron microscopy (SEM), and wide-angle X ray (WAXS). Glass transition temperature of solvent cast materials, detected by dynamic mechanical analysis (DMA), showed partial molecular interactions between PHBV and PLLA. Crystallinity of the PLLA phase slightly decreased with increasing amount of PHBV, confirming the partial dispersion of PLLA in the PHBV phase. Mechanical properties were analyzed with theoretical models able to predict the behavior of heterogeneous systems. Phase separation was confirmed by SEM observations. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070541017
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  • 12
    Electronic Resource
    Electronic Resource
    Dynamic-mechanical and dielectric characterization of PEEK crystallization (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 314-320 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Dynamic-mechanical and dielectric characterization of the cold crystallization of PEEK has been performed in order to develop a non-destructive evaluation method of crystallinity in thermoplastic matrices. The Avrami approach is applied here to describe the Poly(ether ether ketone) (PEEK) crystallization kinetics after an appropriate reduction of dynamic-mechanical and dielectric parameters. Avrami exponents obtained from dielectric characterization are comparable with those obtained with DSC measurements reported in literature, while the exponents obtained from the dynamic-mechanical characterization are higher, reflecting also changes in the aspect ratio of the growing crystals. Variations in the glass transition temperature detected during cold crystallization are analyzed and analogies between PEEK and PET are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300509
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  • 13
    Electronic Resource
    Electronic Resource
    Dielectric characterization of water sorption in epoxy resin matrices (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 75-82 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Water sorption in epoxy based materials was analyzed by dielectric spectroscopy using remote sensors. A method to determine diffusion coefficients from the changes in permittivity during water absorption is proposed and was verified experimentally by comparison with standard water gain measurements. Although the technique is limited by electrode polarization phenomena, it is sensitive to the presence of water molecules and is capable of detecting different levels of water concentration as a function of frequency. The utilization of remote sensors demonstrated the capability of dielectric analysis to be applied both in the laboratory environment, and on a larger scale, as a nondestructive technique for monitoring environmental changes in actual polymer matrix composite parts.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760330204
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  • 14
    Electronic Resource
    Electronic Resource
    Macrophage activation induced by different carbon fiber-epoxy resin composites (1991)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 25 (1991), S. 637-649 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The activation of cells by interaction with solid surfaces is important in many settings, including the response of tissue to implanted materials. However, few comprehensive studies of both cell migration and activation have been performed so that the connection between these events and immunological activation against foreign material is not well understood. In the present study, synthesis and expression of Ia antigens by peritoneal exudate macrophages after implantation of different carbon fiber composites in the rat peritoneal cavity have been investigated in order to determine whether the type of material implanted affected the composition of Ia-bearing cells of the exudate. The results have confirmed the low level of expression of Ia on resident peritoneal macrophages; while we have found that macrophages, harvested after implantation, express a different amount of Ia related to the different cure cycles of the composite materials used.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820250507
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  • 15
    Electronic Resource
    Electronic Resource
    The influence of a copolymer as adhesion promoter for polycarbonate and liquid crystalline polymer blends (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 83-94 
    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: The modification of the interface between polycarbonate (PC) and Pet Phb60 was studied. The ester interchange reaction between the components of the 50% w/w mixture, responsible for the formation of molecular segments of intermediate affinity toward the parent polymers, has greatly affected the morphology of extrudate samples. The reacted compound was used in the ratio of 5% as compatibilizer in the formulation of the in situ composite between PC and PetPhb60, containing 10% of the reinforcing thermotropic liquid crystal polymer (TLCP). The effects of the adhesion promoter has been evaluated comparing the morphological features of melt-drawn fibers with the previous result concerning the fibers without the compatibilizer. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070500111
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  • 16
    Electronic Resource
    Electronic Resource
    Gas-transport properties of ethylene/propylene/carbon monoxide polyketone terpolymer (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 1261-1268 
    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: The demand for heat-stable and easily processable polymeric materials with good gasbarrier properties is becoming more and more important due to the advent of new technological applications in the field of food packaging. A renewed interest has arisen for a polyketone class of polymers, which seems to fulfill these requirements. Our attention has been focused on a polyketone terpolymer (0.93 : 0.07 : 1 ethylene/propylene/carbon monoxide) in order to determine the transport properties and to relate them to the polymer structure. Permeability tests have been performed at three different temperatures (25, 35, and 45°C) with three different gases (helium, oxygen, and carbon dioxide). Permeabilities, diffusivities, and solubilities have been evaluated. Their dependence on temperature was interpreted on the basis of permeation and diffusion apparent activation energies (Ep and Ed) and of heats of solution (ΔHs). The investigated polymer has been found to be rubbery at the test temperature (glass transition temperature is about 17°C), but the detected permeabilities are comparable to those of glassy polymers widely used for packaging applications. The experimentally determined diffusion coefficients have been related to the semicrystalline nature of the polymer and to the different dimensions of the gas adopted in the investigation. The gas-solubility coefficients determined from permeability measurements were related to the force constant of the gas molecules in the Lennard-Jones (6-12) potential field equation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070500717
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  • 17
    Electronic Resource
    Electronic Resource
    In vivo induction of macrophage Ia antigen (MHC class II) expression by biomedical polymers in the cage implant system (1994)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 635-646 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Examination of the cellular components in the inflammatory exudate, which infiltrates subcutaneous cages, can be used to monitor the progress of an inflammatory response to an implanted material. Of particular interest is the study of monocyte/ macrophage infiltration into the implanted cages containing biomaterials, as macrophages may initiate a wide spectrum of responses upon interaction with a foreign material. In this study, the authors propose a technique using subcutaneous tissue cages in conjunction with cytofluorimetric analysis of exudate leukocytes to evaluate the monocyte/macrophage cell activation in response to different materials. The studies reported here used several materials. The studies reported here used several materials (thermoplastic and elastomeric polymers) as the challenging agent, to demonstrate whether polymers, chemically different from each other, could differentially activate macrophages to carry out their proinflammatory role more effectively. The materials tested included: poly(etherurethane ureas) (PEUU A'), poly(etherurethane ureas) with a surface active additive, Methacrol®, (PEUUC'), polymethylsiloxane (PDMS), polyetherimide, (PEI), and polyetheretherketone, (PEEK). For all the tested materials, the maximum numbers of exudate cells and of Ia-positive macrophages were found on day 7, although the entity of the cell increase was associated with the material used for the implant. Similarly, the percentage of Ia-positive macrophages varied according to the specific polymer present in the cages after 7 days. By day 14, the percentage of Ia-positive macrophages decreased with individual exudates showing 19-32% Ia-positive cells depending on the different type of material. Only in the case of PDMS did the percentage of Ia-positive macrophages remain the same as compared with control empty cage macrophages. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820280514
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  • 18
    Electronic Resource
    Electronic Resource
    Mathematical modeling of the pultrusion of epoxy based composites (1990)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 10 (1990), S. 251-264 
    Details
    ISSN: 0730-6679
    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
    Notes: The thermokinetic and rheological behavior of epoxy based composites during the pultrusion of carbon fiber composites is analyzed using a mathematical model accounting for the heat transfer and the heat generation characteristics of polymerizable systems. An energy balance and a kinetic expression for the chemical reaction are simultaneously solved to calculate the temperature and degree of reaction profiles. Afterwards the viscosity as a function of the degree of reaction is computed applying a theoretical model. The dimensionless mathematical model is applied to the description and optimization of the process variables. General optimization criteria are identified and applied to compute, through a tailored numerical simulation, the optimum set of processing conditions for different case studies corresponding to different die temperatures, pulling speeds, and composite thicknesses.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adv.1990.060100402
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