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  • Chemistry  (4)
  • 13C NMR
  • Biorestoration
  • 1975-1979  (4)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 95-98 
    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: Glassy crosslinked networks were prepared by copolymerization of methyl methacrylate with up to 4.7 mole-percent ethylene dimethacrylate. These networks were degraded by exposure to γ-rays and the solubilized fraction estimated by benzene extraction using the analysis of A. R. Schultz. The efficiency of the Crosslinking agent was found to be 0.5 and this value was used to calculate the molecular weight between crosslinks. The molecular weight of the primary molecules in the network, M, was estimatfrom the radiation dose using the known fact that one fracture requires an energy deposition of 59 ev. Crosslinking was found to have little influence on the tensile strength of networks of primary molecular weight 〉 105. In contrast. crosslinking raised, the strength of polymers of M 〈 105 to, a value approaching that of a high molecular weight linear polymer (ca. 70MN/m2). Crosslinking was found to have only a small influence on the gross morphology of fracture surfaces.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 11 (1977), S. 671-676 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The peak temperature reached during the polymerization of a bone cement was reduced by addition of solid N-vinylcarbazole to the powder component. It was also necessary to saturate the liquid component with N-vinylcarbazole to prevent dissolution from the modified powder component on mixing. It is believed that this technique is generally applicable and opens up the possibility of achieving temperature control of bone cements with choice from a range of crystalline monomers.
    Additional Material: 1 Ill.
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  • 3
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An investigation was made of the influence of application techniques on the microstructure and properties of an acrylic tooth restorative. Mixtures of acrylic powder and monomer (“Sevriton Simplified”) were applied by the brush technique of Nealon (J. Prosth. Dent., 2, 513, 1952) and by two bulk flow techniques. While similar porosities (about 4%) were observed, the brush technique resulted in a greater quantity of grains from the acrylic powder. Despite this, there was little difference in values of compression modulus, compressive yield stress, and diametral compressive strength.The mechanical strength of the materials studied was less than one-half that of high molecular weight poly (methyl methacrylate) (PMMA). Crack propagation studies established that the interface between the grains and matrix was not a source of weakness. However, as the matrix was crosslinked this could not be checked by solution methods of polymer characterization.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 9 (1975), S. 89-98 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: For convenience in clinical manipulation, it is the practice to fabricate PMMA prostheses from mixtures of powder and monomer. When the monomer is subsequently polymerized an unusual 2-phase polymeric material results in which grains of PMMA are dispersed in a matrix of the same polymer.The mechanical properties of the 2-phase materials are inferior in certain respects relative to 1-phase polymers.The purpose of the present work is to evaluate the failure of 2-phase materials by microscopical examination of their fracture surfaces. A granular microstructure was clearly distinguishable and a distinction made between materials which fail exclusively by transgranular fracture and others which additionally exhibit intergranular fracture.In order to interpret markings observed on the fracture surfaces of the complex 2-phase systems a study was made of the influence of molecular weight on the fractography of 1-phase PMMA. Molecular weight was reduced by degradation of samples by exposure to γ-rays. The spacing of periodic rib markings on fracture surfaces was found to decrease with molecular weight and this relationship used to provide an estimate of the molecular weight of polymer in the matrix of 2-phase materials.
    Additional Material: 5 Ill.
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