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  • Polymer and Materials Science  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Molecular and macroscopic properties of PMMA bone cement: Free-radical generation and temperature change versus mixing ratio (1981)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 425-432 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The molecular and macroscopic changes occurring during the polymerization of poly(methyl methacrylate) (PMMA) bone cement have been investigated. Electron paramagnetic resonance (EPR) spectroscopy was used to monitor free-radical generation and this was compared to temperature changes occurring in the cement for various ratios of polymer powder to liquid monomer (P/L ratio) used in the sample preparation. Both the concentration and the characteristic growth time of the free radicals associated with the polymerization of the bone cement depended on the P/L ratio used. Larger P/L ratio resulted in shorter characteristic growth time for the free radicals as well as a shorter time for the occurrence of the peak sample temperature. Smaller P/L ratios gave smaller maximum concentrations of free radicals and larger peak temperatures. These results are explained on the basis of (1) more initiators present at higher P/L ratios resulting in faster polymerization and (2) less initiators and more monomers present at smaller P/L ratios resulting in fewer radicals but more exothermic reactions. The free radicals present in the bone cement due to the manufacturer's sterilization process were found to be proportional to the fraction of powder used in the preparation, indicating negligible monomer loss during sample mixing.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820150312
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of initial temperature on free radical decay in PMMA bone cement (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 639-646 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effect of varying the initial temperature of the components of poly(methyl methacrylate) (PMMA) bone cement has been investigated. Electron paramagnetic resonance (EPR) spectroscopy was used to monitor free radical decay during the curing of the cement. Samples cured in saline at 37°C were found to exhibit first-order decay kinetics for the polymerization radicals for approximately one week after mixing. This indicates that the decay did not take place by combination or disproportionation and was probably due to a transfer process. Decreasing the temperature of the bone cement components prior to mixing resulted in smaller decay rates, but still with first-order kinetics. This decrease in decay rate with lower initial temperature may be due to decreased porosity of the cement, possibly due to decreased monomer evaporation. SEM micrographs of the samples were consistent with this change in porosity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820160511
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  • 3
    Electronic Resource
    Electronic Resource
    Free radical decay kinetics in PMMA bone cement (1984)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 18 (1984), S. 467-473 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Electron-spin resonance has been used to measure the decay of the concentration of polymerization radicals in polymethyl methacrylate (PMMA) bone cement and the kinetics of the decay determined. Thermal annealing at various temperatures has shown that the logarithm of the concentration of radicals varies linearly with time, but with a nonzero intercept. These results have been analyzed by including both first- and second-order decay processes. The first-order process has an activation energy of 39 ± 2 kcal/mol and is probably due to a diffusion-limited termination. The second-order process has an activation energy of 36 ± 5 kcal/mol and is probably due to bimolecular termination.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820180502
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