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  • 1
    Electronic Resource
    Electronic Resource
    Shrinkage effects in photopolymerizable resins containing filling agents: Application to stereophotolithography (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2715-2723 
    Details
    ISSN: 0887-624X
    Keywords: shrinkage effects ; photopolymers ; stereophotolithography ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of porous additives with various structures on the shrinkage of resins used for stereolithographic applications was studied by measuring the dependence of the specific gravity of the charged polymer material as a function of the charge fraction. The investigations were conducted on difunctional monomers photopolymerized either by a radical (acrylate) or a cationic (epoxy) mechanism. The improvement resulting from the incorporation of charges in the formulation is accounted for in a semi-quantitative way by an adsorption-desorption equilibrium of monomer molecules between the pores and the bulk phase. Thus, the pores of the charges which are initially filled with monomer molecules play the role of buffers which discharge their content as the photopolymerization develops in the liquid phase. It is also worth mentioning that the viscosities of the photosensitive charged resins used in these experiments are quite suitable for use in stereophotolithography. © 1992 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080301307
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  • 2
    Electronic Resource
    Electronic Resource
    Experimental determination of the light distribution in a photochemical reactor: Influence of the concentration of an absorbing substance on this profile (1982)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 156-166 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Knowledge of the local distribution of the light energy, in a photochemical reactor in the presence of an absorbing substance which reacts at a rate of order different from one with respect to the adsorbed light intensity, is important in order to calculate the mean rate of reaction and the design of the reactor. Here we report a simple method for the determination of this profile as a function of the concentration of an absorbing substance and we compare the results obtained with the models of emission from the literature. A semi-empirical model accounting for our experimental results is presented.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690280123
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetics of partly diffusion-controlled reaction XXI: A simple algorithm for computing the apparent rate of reaction (1989)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 297-314 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from Smoluchowski's hypothesis, a simple algorithm is developed in order to obtain the apparent rate constant at large values of time, t, with some physical and chemical processes, as in the case of diffusion controlled reactions. Some practical examples are illustrated, assuming nonuniform distribution function, space-dependent diffusion coefficient or short-range interaction leading to an asymptotic analytical expression of the form α + β/√t, where α and β are constants function of the system of interest.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550210502
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetics of partly diffusion-controlled reactions. XIV. Effects of reversible energy transfer (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 407-421 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The general effect of back energy transfer is to reduce the apparent quenching constant which is an important parameter in the interpretation of energy transfer data. However, this interpretation may be erroneous when possible diffusion effects and the existence of nonuniform configurational distributions are not taken into account.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550160410
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  • 5
    Electronic Resource
    Electronic Resource
    Radiationless transitions between excited singlet states of biacetyl (1978)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 10 (1978), S. 213-226 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Emission processes from lower excited states S1 (fluorescence) and T1 (phosphorescence) have been studied in the gas and liquid phases when biacetyl is excited into the second singlet state S2. (In agreement with Kasha's rule no fluorescence is observed from the S2 state.)In the liquid phase, when biacetyl is excited into the singlet states S1 and S2, no difference is observed between these emission processes. This phenomenon certainly results from an efficient nonradiative transition between the second excited singlet state S2 and the first excited state S1 with practically no excess vibrational energy. The quantum yield of this transition is almost unity and does not depend on the nature of the solvent.In the gas phase no emission processes are observed when biacetyl is excited into the S2 state at low pressure (less than 10 mm Hg). High pressure of inert gas is necessary in order to observe these processes. As for excitation into the S1 state with vibrational energy, loss of vibrational energy through collisions occurs from the S2 state. The quantum yield of the S2 → S1 transition by excitation at 290 nm is estimated around 0.5-0.6 at 6 atm of inert gas (ethane, ethylene, or carbon dioxide).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550100207
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