Photocuring and thermal post-curing of a cycloaliphatic epoxide resin with a trithiol and a vinyl epoxy compound
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In this work, the influence of trimethylolpropane tris-(3-mercaptopropionate) and a vinyl epoxy compound (4-vinyl-1-cyclohexene 1,2-epoxide) over the photocuring and subsequent thermal curing of an epoxy resin (CYRACURE UVR-6105) is studied. The photoinitiator used is CYRACURE UVI-6976. The techniques used in this study have been DSC (differential scanning calorimetry) and FTIR (Fourier transform infrared spectroscopy). In the isothermal photocuring, when the proportion of the modifiers are 5 % or greater, the photopolymerization of the epoxy resin is stopped by the thiol-ene reaction of both modifiers, due to the formation of alkyl sulfonium salts, decreasing the maximum degree of conversion of the process. After the photocuring process, the different systems studied have been post-cured thermally and the activation energy of this process has been determined using a differential isoconversional method. When the epoxy resin is neat or only it has been added 2.5 % of the modifiers, at the beginning of the post-curing the activation energy decreases, but when the proportion of the modifiers is 5 % or greater, the activation energy always increases.
KeywordsEpoxy networks Thiol-ene Photocuring Thermal curing Kinetics
The authors would like to thank MICINN (Ministerio de Ciencia e Innovación) and FEDER (Fondo Europeo de Desarrollo Regional) (MAT2011-27039-C03-01 and MAT2011-27039-C03-02 and contract JCI-2010-06187) and to the Comissionat per a Universitats i Recerca del DIUE de la Generalitat de Catalunya (2014-SGR-67).
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