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  • Articles  (18)
  • Polymer and Materials Science  (15)
  • Aphidius sonchi  (3)
  • ASTROPHYSICS
  • 1990-1994  (6)
  • 1980-1984  (12)
  • 11
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 3467-3473 
    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: Binary blends of poly(vinyl chloride) and a poly(ether urethane) containing 20 and 40 weight percent, respectively, of poly(vinyl chloride) have been prepared by solution blending from tetrahydrofuran and their degree of mixing investigated using dynamic mechanical analysis. In the polyurethane, transitions were found at -19°C and -119°C. The former was attributed to the glass transition and the latter to a Schatzki type of motion of the polyether sequences. This latter transition occurred at a temperature which is higher than the literature value for the low temperature transition in poly(tetrahydrofuran), which is equivalent to the polyether sequence in the polyurethane. This discrepancy is attributed to the influence of neighboring hard segments present because of incomplete segmental phase separation of the polyurethane. For the blends only one very broad transition was observed, indicating that there was substantial mixing of these two polymers. Three ternary blends were prepared, also by solution blending, containing poly(vinyl chloride), Hytrel, and the polyurethane in the ratios 1:1:1, 1:2:1, and 2:1:1, respectively. In the first two blends there was clear evidence of phase separation. It was only in the 2:1:1 blend that an apparently significantly compatible material resulted.
    Additional Material: 6 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 3487-3491 
    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 solution blend of poly(vinyl chloride) and a segmented poly(ether ester) and blends containing these two polymers plus poly(methyl acrylate) were investigated by dynamic mechanical analysis and electron microscopy. The binary blend, which contained 75% by weight of the poly(ether ester), showed only one loss peak, but also evidence of some phase separation. It is believed that the polyether sequences of the poly(ether ester) are extensively mixed with poly(vinyl chloride). Poly(methyl acrylate) was added to spread the damping range and produce a material of potential use as an acoustic damper. It is evident from both electron microscopy and dynamic mechanical analysis that poly(methyl acrylate) is substantially incompatible in the other polymers.
    Additional Material: 4 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 24 (1990), S. 79-94 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An accelerated anodic corrosion method was used to study the effects of heat treatment and bead size on corrosion and metal ion release of porous coated F75 cylinders in saline and serum. Three heat treatments were used: a standard process for F75 implants (HTA), the standard plus an additional hour in air to produce a thin oxide film (HTA′), and a sintering in high vacuum to produce a chromium-depleted surface (HTB). Three bead sizes of similar composition were used, with approximate sizes of 215, 300, and 560 μm. The results demonstrated that HTA′ had the lowest corrosion rate and that of HTB was significantly greater than either HTA or HTA′. The corrosion rates of HTA and HTA′ were significantly greater in serum as compared with saline, whereas that of HTB was not affected by the presence of serum, suggesting an interaction between chromium and serum proteins. Bead size had a minimal effect on the corrosion rate of HTA′. For HTA, the small beads had the highest corrosion rate; the lowest was with the medium-sized beads. Bead size had the most significant effect with HTB, with that of the smaller beads having the higher corrosion rates. The effects of bead size were less consistent in serum, suggesting that protein adsorption may mask some of the surface area effects. It is concluded that the oxide film does reduce corrosion, that proteins do have an influence on the corrosion of F75, and that this method can be a suseful tool for studying the effects of improved heat treatment methods on the corrosion rate of F75 implants.
    Additional Material: 4 Ill.
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  • 14
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The tissue response and in vivo molecular stability of injection-molded polyhydroxyacids - polylactides (PLA), poly(3-hydroxybutyrate) (PHB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB/VA, 5-22% VA content) - were studied. Polymers were implanted subcutaneously in mice and extirpated at 1, 3, and 6 month in order to study tissue response and polymer degradation.All polymers were well tolerated by the tissue. No acute inflammation, abscess formation, or tissue necrosis was observed in tissues adjacent to the implanted materials. Furthermore, no tissue reactivity or cellular mobilization was evident remote from the implant site. Mononuclear macrophages, proliferating fibroblasts, and mature vascularized fibrous capsules were typical of the tissue response. Degradation of the polymers was accompanied by an increase in collagen deposition. For the polylactide series, the inflammatory response after 1 month of implantation was less for materials containing the D-unit in the polymer chain, whereas in the case of the polyhydroxybutyrate/valerates, the number of inflammatory cells increased with increasing content of the valerate unit in the polymer chain. Between 1-3 months, there was slightly more tissue response to the PHB and PHB/VA polymers than to PLA. This response is attributed to the presence of leachable impurities and a low molecular weight soluble component in the polyhydroxybutyrate/valerates. At 6 months, the extent of tissue reaction was similar for both types of polymers.All polylactides degraded significantly (56-99%) by 6 months. For a poly(L-lactide) series, degradation rate in vivo decreased with increasing initial molecular weight of the injection-molded polymer. Several samples showed pronounced bimodal molecular weight distributions (MWD), which may be due to differences in degradation rate, resulting from variability in distribution of crystalline and amorphous regions within the samples. This may also be the result of two different mechanisms, i.e., nonenzymatic and enzymatic, which are involved in the degradation process, the latter being more extensive at the later stage of partially hydrolyzed polymer. The PHB and PHB/VA polymers degraded less (15-43%) than the polylactides following 6 months of implantation. Generally, the polymer with higher valerate content (19%, 22% degraded most. The decrease in molecular weight was accompanied by a narrowing of the MWD for PHB and copolymers; there was no evidence of a bimodal MWD, possibly indicating that the critical molecular weight that would permit enzyme/polymer interaction had not been reached. Weight loss during implantation ranged from 0-50% for the polylactides, whereas for the PHB polymers weight loss ranged from 0-1.6%. © 1993 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 16 (1992), S. 119-125 
    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: This study is based on the use of integral, hybrid thermal barrier to protect the core of the composite structure. Thermal barrier treatments evaluated in this study include ceramic fabric, ceramic coating, intumescent coating, hybrid of ceramic and intumescent coating, silicone foam, and phenolic skin. The composite systems evaluated in combination with thermal barrier treatments included glass/vinyl ester, graphite/epoxy, graphite/bismaleimide, and graphite/phenolic. All configurations were tested for flammability characteristics. These included smoke density and combustion gas generation (ASTM E-662), residual flexural strength (ASTM D-790), heat release rate, and ignitability (ASTM E-1354). ASTM E-662 test method covers the determination of specific optical density of smoke generated by solid materials. ASTM D-790 test method covers the determination of flexural properties of composite materials in the form of rectangular bars. ASTM E-1354 (cone calorimeter) covers the measurement of the response of materials exposed to controlled levels of radiant heating with or without an external ignitor, and is used to determine the ignitability, heat release rates, mass loss rates, effective heat of combustion, and visible smoke development. Without any fire barrier treatments, all composite systems evaluated in this study failed to meet ignitability and peak heat release requirements of MIL-STD-2031 (SH) at radiant heat fluxes of 75 and 100 kW m-2, respectively. Intumescent coating and a hybrid system consisting of intumescent coating over ceramic coating were the most effective fire barrier treatments for composite systems evaluated in this study. Using either of these treatments, all composite systems met the ignitability requirements of 90 and 60 at 75 and 100 kW m-2, respectively. Except for glass/vinyl ester, all systems also met the peak and average heat release requirements of MIL-STD-2031 (SH) at radiant heat fluxes of 25, 75, and 100 kW m-2, respectively.
    Additional Material: 7 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 1001-1012 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Samples of polyethylene and polytetrafluorethylene were sintered at 200°C. The samples were cleaved and cut, and the two types of surfaces were studied by ESCA. The possibility of chemical interaction between the two polymers and the formation of a transitional layer is postulated on the basis of the results. A morphological model of the structure of these samples is given.
    Additional Material: 9 Ill.
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  • 17
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The electron energy analyser transmission (peak area/incident current) of a VG Scientific ESCALAB has been measured as a function of kinetic energy, analyser energy and source position for a point source of electrons in the sample plane (produced using a specially designed mini electron gun). Results have been obtained in both CAE (constant analyser energy) and CRR (constant retard ratio) modes. The results are extrapolated to give the energy dependence of the analyser transmission for an extended current source, such as encountered in routine XPS analysis applications. A detailed theoretical study explains the rationale behind this data extrapolation and predicts an analyser transmission in fair agreement with experimental results, possible causes for the discrepancies between theory and experiment are discussed.
    Additional Material: 13 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 8 (1984), S. 148-156 
    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: An empirical relation has been developed which correlates and predicts the fire-suppression effectiveness of a wide variety of gaseous, liquid and solid agents. The flame-extinguishment model is based on the premise that extinction is dominated by heat-absorption processes and that a flame is extinguished when sufficient heat has been removed by the extinguishant to reduce the temperature to a limit value. This limit value. This limit is the minimum temperature at which the effective rate of the combustion reactions is sufficient to maintain flamepropagation, and it depends in a predictable way on the properties of the suppressant and flame system. The heat-balance equation describing this is derived in two stages. In the first, a preliminary equation is obtained by considering only those substances which are thermally stable and act only as heat-capacity sinks. In the second, the equation is generalized by consideration of all endothermic reaction sinks, e.g. vaporization, dissociation and decomposition. The general equation correlates most of the extinction data found in the literature. The results suggest that for most substances the extinguishing capacity is related to heat-extraction data found in the literature. The results suggest that for most substances the extinguishing capacity is related to heat-extraction and that many of the effects previously attributed to chemical mechanisms may be thermodynamic in nature rather than kinetic.
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