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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 5 (1994), S. 56-62 
    ISSN: 1042-7147
    Keywords: Photoinitiator ; Photopolymerization ; Laser imaging ; Laser spectroscopy ; Photochemistry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The design of an efficient photosenzitizer/photoinitiator combination is partly governed by a better understanding of the excited state processes involved. In the present paper, the photochemistry of a thiopyrylium salt (TP) as photosensitizer and of a tetraperester of benzophenone, tetra t-butyl peroxycarbonylbenzophenone (BTTB) as initiator, used in laser imaging applications has been investigated. The reactivity of the triplet states of both compounds BTTB and TP was studied by time-resolved laser absorption spectroscopy. The laser excitation of TP leads to a long-lived triplet state (lifetime 20-25 μsec) and a second species arising from the triplet state which cannot yet be characterized. Under laser excitation, BTTB gives a longlived transient arising from the cleavage of the peroxy bond. The short-lived triplet state cannot be observed on the nanosecond timescale. The triplet state lifetime has been evaluated from quenching experiments and found to be about 1 ns in acetonitrile. The deactivation of the TP triplet state by BTTP was considered, the deactivation constant was found to be equal to 6.6 × 107 m-1/sec in acetonitrile. The initiation mechanism is discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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