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  • Polymer and Materials Science  (140)
  • 1
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of styrene oxide by nitronium tetrafluoroborate in nitromethane and methylene chloride at 5, 20, and 50°C is investigated. GPC analyses of the products combined with isocyanate method show that both cyclic and linear oligomers are formed. In CH3NO2 the cyclic dimer and trimer are 2-benzyl-4-phenyl-1,3-dioxolane and 1,3,5-tribenzyl-trioxane, respectively. In CH2Cl2 2,5-diphenyldioxane is isolated. In nitromethane, mainly isomerized structures with acetal linkage are produced, while in methylene chloride isomerization does not proceed. By NMR and IR spectra the presence of C=O and OH end groups in the linear oligomers is shown. There are indications that oligomers are formed both directly from the monomer and by degradation of the polymer.
    Additional Material: 6 Ill.
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  • 3
    ISSN: 0887-624X
    Keywords: fluoropolymers ; low dielectric constant ; thermally stable ; aromatic polyethers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of fluorinated aromatic polyethers was synthesized via aromatic nucleophilic substitution of highly fluorinated aromatics (1,2,4,5-tetrafluorobenzene, hexafluorobenzene, and decafluorobiphenyl) with bisphenol AF or bisphenol A. Polymerization with 1,2,4,5-tetrafluorobenzene was not observed, and polymerization of hexafluorobenzene with bisphenol proceeded only if the potassium carbonate-bisphenol ratio was carefully controlled. The polymer condensed from decafluorobiphenyl and bisphenol AF was prepared in 77% yield with an inherent viscosity of 1.01 dL/g. The polymer prepared from the condensation of decafluorobiphenyl with bisphenol A was obtained in 48% yield with an inherent viscosity of 0.28 dL/g. These polymers were very soluble in common organic solvents, formed clear, colorless films, and were thermally stable (〉 450°C by TGA). The fully fluorinated polymer exhibited low water uptake (0.3%) and dielectric constant (2.17). © 1992 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 4
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFT15), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFT15 material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFT15 had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFT15. The final conclusion is that in this model, grafting with COLLAGRAFT15 provided torsional properties at one year postoperatively at least equivalent to autogenous bone. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 5
    ISSN: 0887-624X
    Keywords: poly(p-phenylenebenzobisthiazole) ; poly(p-phenylenebenzobisoxazole) ; fiber ; molecular composite fiber ; benzocyclobutene ; compressive strength ; tensile strength ; tensile modulus ; phase separation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fibers consisting of a rigid rod polymer and thermoset resin matrices were prepared. Poly(benzo-[1,2-d : 5,4-d′]bisoxazole-2,6-diyl)-1,4-phenylene} (PBO) in polyphosphoric acid (PPA) was blended with isophthaloyl bis-4-benzocyclobutene (1) or 2,6-bis-4-benzocyclobutene benzo[1,2-d: 5,4-d′]bisoxazole (2), and fibers were spun from these dopes. As-spun fibers that did not show phase segregation between the two components as examined with an optical microscope, were soluble in methanesulfonic acid (MSA). After heat treat-ment, the fibers swelled but did not dissolve in MSA. A fiber cross section of heat-treated PBO-1 fiber showed well-dispersed benzocyclobutene polymer domains of 200-500 Å by transmission electron microscopy (TEM). Films cast from MSA solutions of PBO and 2 were homogeneous, and TEM of heat-treated fiber showed only one phase. A molecular composite fiber was made. Some of these fibers showed 20-30% improvement in compressive strength over unmodified PBO fiber. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 6
    ISSN: 0887-624X
    Keywords: poly(p-phenylenebenzobis(thiazole)) ; poly(p-phenylenebenzobis(oxazole)) ; film ; molecular composite ; benzocyclobutene ; phase separation ; interlayer integrity ; tensile strength ; tensile modulus ; delamination resistance ; film density ; coefficient of thermal expansion ; thermal stability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Films consisting of a rigid-rod polymer and thermoset resin matrixes were prepared. Poly{(benzo[1,2-d : 5,4-d′]bis(oxazole-2,6-diyl))-1,4-phenylene} (PBO) in polyphosphoric acid (PPA) was blended with 2,6-bis(4-benzocyclobutene) benzo[1,2-d : 5,4-d′]bis(oxazole) (1), and films were extruded from these solutions. The coagulated films were soluble in methanesulfonic acid (MSA). After heat treatment at 300°C, the films became insoluble in MSA. Crosslinked films were homogeneous and did not show phase segregation between the two components. These were composite films at the molecular level. Transmission electron microscopy (TEM) showed enhanced interlayer integrity and reduced microfibril separation for the molecular composite films as compared to normal PBO film. These films had significantly better torsion and tension delamination resistance. The incorporation of a second component did not sacrifice the tensile properties of PBO film. Thermal stability of these composite films was only slightly lower than that of normal PBO film. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2157-2165, 1997
    Additional Material: 8 Ill.
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  • 7
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Previous nuclear magnetic resonance measurements on a polymethylsiloxane gum (MW = 75,000) had been interpreted to indicate the presence of considerable segmental motion in both the amorphous and crystalline components at temperatures above the glass temperature. Further investigation again showed the NMR line to be completely narrowed just above the glass point indicating such motions must extend into the crystalline component. This work was extended by the measurement of NMR absorption line widths for temperatures of 80-300°K. on samples of the same gum subjected to gradually-increased crosslinking by electron doses of 3-600 × 106 rep. Here, no change in the NMR properties of low temperature, rigid states were observed, but the room temperature line width progressively increased from 0.019 gauss to over 0.100 gauss peak-to-peak due to the increase in bulk viscosity of the liquid. The “first-order” activation energy associated with the temperature-dependent line narrowing decreased from 10 to 2 kcal./mole. The NMR data indicate that the primary effects of radiation-induced crosslinking are to reduce the chain rotational energy by the creation of defects and to increase the short-range viscosity by the lowering of translational freedom.
    Additional Material: 5 Ill.
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  • 8
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the light of special applications, trials were carried out on the separation of steel tubes using commercially obtainable explosive cutting charges in an annular configuration in order to find out their cutting performance and the effects on the environment incurred during separation. Tubes made of St37 steel having a diameter of 220 mm and a wall thickness of 10 mm as well as tubes consisting of hightensile 15 Mo 3 steel with a diameter of 273 mm and a wall thickness of 12.5 mm were used for this purpose. It was possible to cut the tubes accurately and neatly with the charges used. However, the projectiles formed during the detonation process are not compact, for which reason the cutting performance of the commercial charges used is not optimal. There is here a considerable potential for improvement. Measurements of the environmental effects conducted during the trials (fragmentation, blast wave, projectile impact on tube line) show that the incidental effects of explosive tube cutting are controllable.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystals of amylose were prepared by precipitation from aqueous solution with n-butanol. The crystals are rectangular platelets, and crosses or rosettes formed by the intergrowth of single platelets. In the electron microscope they are seen to consist of layers 75 A. in thickness. Distinct spiral terrace growths related to screw dislocations were not observed, but the presence of dislocation edges suggests that the crystals thicken by a dislocation mechanism. Low-angle, x-ray measurements on aggregates of the crystals reveal a long spacing in good agreement with that calculated from shadow lengths. However, in contrast with other polymers, the long spacing appears to be invariant with crystallization temperature. Electron diffraction spot patterns show that the platelets are single crystals and indicate that the chain molecules are folded within the lamellae.
    Additional Material: 8 Ill.
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