Cationic Polymerization (Cure Kinetics) of Model Epoxide Systems

Report No. ARL-TR-2714
Authors: Reza Dabestani, Ilia N. Ivanov, and James M. Sands
Date/Pages: April 2002; 45 pages
Abstract: Cationic polymerization of epoxy resins can be induced by ultraviolet (UV) or electron beam (E-beam) radiation and proceeds very efficiently in the presence of an appropriate photoinitiator. Although good thermal properties have been obtained for some E-beam cured epoxy resins, other important mechanical properties, such as interlaminar shear strength, fracture toughness, and compression are poor and do not meet aerospace manufacturers materials standards. We have initiated a comprehensive study to investigate the cure kinetics and mechanisms of UV and E-beam cured cationic polymerization of two epoxide-terminated resins (phenyl glycidyl ether (PGE), a monofunctional model compound, and Tactix 123, a difunctional structural resin) cured using a mixed triaryl iodonium hexafluoroantimonate salt (Sartomer's CD-1012) photoinitiator. The objective of this study was to demonstrate that identical reaction conditions and kinetic parameters (e.g., radiation dose, initiator concentration, and reaction temperature) control the physical and chemical properties of final polymeric products, regardless of initiation by UV or E-beam radiation. Additionally, the identification of key parameters that give rise to improved thermal and mechanical properties in E-beam processed resins is sought. Fast kinetic spectroscopy, coupled with high-performance liquid chromatography, was used to elucidate the polymerization mechanism and to identify the reactive intermediates, or molecules, involved in the cure process.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 2002