IN-SITU CURE MONITORING OF DIAMINE CURED EPOXY BY FIBEROPTIC FLUOROMETRY USING EXTRINSIC REACTIVE FLUOROPHORE

This paper describes the application of a molecular sensor for in-situ monitoring of epoxy-diamine cure via remote sensing fiberoptic probes . A custom-built, flberoptic fluorimeter allows on-line recording of f luorescence spectra directly from the cure environment. Cure reactions in epoxy-diamine network, such as diglycidyl ether of bisphenol A-dia minodiphenyl sulfone (DGEBA-DDS) or diglycidyl ether of butanediol-dia minodiphenyl sulfone (DGEB-DDS), have been monitored by a reactive mol ecular sensor, diamino azobenzene (DAA). DAA exhibits sensitive change s in UV-visible and fluorescence spectra due to the conversion of its primary amine groups to secondary and tertiary amine groups. Fluoresce nce intensities are correlated with extent of reaction in epoxy networ k and processing parameters, such as cure temperatures and time. The u se of an internal reference dye for normalization of fluorescence inte nsities is necessary for the quantitative correlation of spectral sign als with the network structure. Variables affecting the fluorescence i ntensity such as excitation volume, probe location, excitation intensi ty fluctuation. temperature, and background intensities from optical f iber can be calibrated by normalizing the signal intensities against t he internal reference. Sulforhodamine 101 was found to be a satisfacto ry reference dye which provides stable, readable signals over temperat ures up to 200-degrees-C.