Monitoring Epoxy Cure Kinetics with a Viscosity-Dependent Fluorescent Probe
Properties of carbon-epoxy composites are strongly dependent on the epoxy cure-cycle. Availability of techniques for in situ monitoring of cure kinetics would enhance control of optimized production of composite structures. Experiments are described which exploit the microviscosity dependence of the fluorescence yield of p-(NfN-dialkylamino)benzylidene malononitrile (R. Loutfy, Macromolecules 14 270 (1981)) for monitoring epoxy cure kinetics. Epoxy resins based on either diglycidylether of bi sphenol-A (DGEBA) or tetraglycidyl-d iaminod iphenyl methane (TGDDM) containing 0.5 wt % of the malononi tr ile as a solute probe show an increase of the fluorescence intensity (If) at the probe’s emission band maxima (495 nm) as a function of the degree of cure. Fluorescence-derived profiles for cure kinetics (If as a function of cure time) closely follow the kinetic profiles derived by differential scanning calorimetry (DSC). The fluorescence yield of the TGDDM monomer was found to be viscosity-dependent and therefore, possesses a unique “self-probing” capability which permits monitoring of its viscosity during cure.
This work was performed under the McDonnell Douglass Independent Research and Development Program.
KeywordsDifferential Scanning Calorimetry Fluorescence Quantum Yield Fluorescence Yield Cure Kinetic Initial Fluorescence
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