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  • photopolymerization  (2)
  • Chemical Engineering  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2333-2345 
    ISSN: 0887-624X
    Keywords: dicyclopentenyl acrylate/ethyl acrylate ; photopolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crosslinking efficiency and kinetics of a solid acrylic copolymer DCPA/EA (dicyclopentenyl acrylate/ethyl acrylate) matrix were investigated in the presence of pentaerythritol tetrakis (2-mercaptoacetate) (PETMP) or pentaerythritol tri- and tetraacrylates used as multifunctional crosslinking agents. The reaction of thiol and acrylate addition was sensitized by benzophenone (BP). The crosslinking efficiency of the DCPA/EA - BP - PETMP copolymer system, illuminated at high wavelengths (λ 〉 310 nm), was compared with that of the DCPA/EA matrix alone and the 2-component system copolymer DCPA/EA-BP. The concentrations of photosensitizer and crosslinking agent were varied from 1 to 10 mass %. The kinetics of tetrafunctional thiol addition and cyclopentene (pendant group of the DCPA/EA matrix) disappearance was followed through Fourier transform infrared (FTIR) and by determining the gel content. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2333-2345, 1997
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 633-642 
    ISSN: 0887-624X
    Keywords: excited state ; thioxanthene ; derived dye ; photopolymer plates ; photoinitiators ; photopolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The excited state interactions occurring when a three-component system of thioxanthene derived dye TXD/amine/additive (diphenyliodonium salt, CBr4, benzoyl peroxide, cumene hydroperoxide) is subjected to sensitization processes in the visible range, were investigated through time-resolved absorption spectroscopy, spectrofluorometry, and photolysis. The rate constants of the various operative processes were measured together with the values of the fluorescence quantum yields (e.g. φ f = 0.75 ± 0.07 in methanol) and the lifetimes of the singlet excited state of the dye (e.g. 6 ns in methanol). Singlet state quenching by methyldiethanolamine (MDEA) occurs with a rate constant k = 109 M-1 s-1 in methanol. The reactivity of the triplet excited state of the dye is very low (k = 5.6 × 104 M-1s-1 for the TXD/MDEA interaction). The ketyl radicals that arise from the interaction of the singlet state of the dye with the amine, are quenched by such additives as CBr4 (k = 6.7 × 105M-1s-1), or the onium salts (k = 5.7 × 105M-1 s-1). The calculations of the yields of interaction of the singlet state of the dye with the two components of the system demonstrate that the process of quenching by the amine is the main one (φint = 0.5) compared to that by, e.g., an onium salt (φint = 0.07). Sensitivity of 0.3 mJ cm-2 obtained in a laser scanning system is also reported. © 1996 John Wiley & Sons, Inc.
    Additional Material: 33 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1061-1065 
    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: The choice of photoinitiators is partly governed by the requirement of a high curing speed. Many reactive monomers and efficient photoinitiators have been synthesized and are commercially available. However, improved photoinitiator systems, exhibiting increasingly faster curing speeds and/or increased photosensitivity, are increasingly required. The intrinsic reactivity in the exicited states determines te interest of a given photoinitiator with reference to its efficiency. However, other factors e.g. high molecular absorption coefficients and a broad spectral absorption range, synergistic effects, yellowing, extractability, and th effect on the long-term stability, must be considered as important. An attractive field of research and development is found in the role played by decisive parameters affecting the reactivity of a given structure, such as chemical substitution in well-chosen positions, the character of water solubility, acid release ability, and copolymerization potential. Laser spectroscopy proved a most convenient tool for the real time investigation of the excited state dynamics and the processes involved.
    Type of Medium: Electronic Resource
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