A methodology for characterizing reactive coatings: Time–temperature–transformation (TTT) analysis of the competition between cure,evaporation, and thermal degradation for an epoxy-phenolic system |
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Authors: | S. Gan J. K. Gillham R. B. Prime |
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Abstract: | A methodology, in terms of a macroscopic isothermal time–temperature–transformation (TTT) diagram, is presented for characterizing the changes that occur isothermally in a reactive thermosetting system in which evaporation, cure, and thermal degradation occur. Iso-weight loss contours show the progress of the loss of volatile material (mostly solvent). The gelation contour corresponds to the macroscopic viscosity rising to a definite level. The vitrification contour corresponds to the glass transition temperature (Tg) rising to the temperature of cure (Tcure). Iso-Tg contours show the progress of cure in terms of the easily measured Tg (rather than chemical conversion). The iso-Tg contours also show the influence of thermal degradation competing with cure. Degradation is responsible for difficulties in assigning the glass transition temperature of the fully cured material (i.e., Tg∞). |
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