Dresden 2009 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 10: Polymer Physics I
CPP 10.5: Talk
Monday, March 23, 2009, 19:00–19:15, ZEU 114
Shelf Life of one-component epoxy resin system studied by Positron Annihilation Lifetime Spectroscopy — •M. Q. Shaikh1, K. Raetzke1, F. Faupel1, and P.-L. M. Noeske2 — 1Institute for Materials Science, Chair for Multi-component Materials, Faculty of Engineering, Christian-Albrecht-University of Kiel, 24118 Kiel, Germany — 2Fraunhofer IFAM, 28349 Bremen, Germany.
One-component epoxy formulations consist of epoxy resin, hardener, filler and the accelerator. They are preferred for industrial applications, but unlike two-component epoxy resin systems they have a limited shelf-life. Positron annihilation lifetime spectroscopy (PALS) was used to study the curing behavior of epoxy resins of DGEBA with a hardener of dicyandiamide (DICY), from the initial viscous state of the formulation to the solid state of cured polymer. Several isothermal measurements were done in the temperature range from 50∘C to 80∘C. PALS parameters seem to correlate very well with the curing mechanism in the samples. Gelation was observed as an increase in the intensity of ortho-positronium (o-Ps) and a sharp decrease in the lifetime. Change of (o-Ps) lifetime was used as a measure for the degree of curing. Applying the Johnson-Mehl-Avrami-Kolmogorov approach under reasonable assumptions, these experimentally observed changes could be characterized by determining the growth exponent ’n’ and reaction constant ’k’. Thus, we were able to extrapolate the shelf life of this particular one component epoxy formulation at room temperature. Acknowledgements. This work was supported by the BMBF (03X0026F ’Nanomodule’).