Fluorescence probe studies during the curing of epoxy systems

Abstract

The curing of bisphenol-A-diglycidylether with diaminodiphenylmethane has been investigated by monitoring the fluorescence decay of relaxing stilbazolium dyes. Because these compounds show a very strong viscosity-dependent fluorescence, it is possible to obtain information about the rotational mobility of the probe within the curing system investigated. The conversion degree of epoxy groups was determined by Raman spectroscopy. Further, the time of gelation was measured by a cycloviscograph (torque measurement). Results obtained by Raman spectroscopy and torque measurements are compared with data obtained by time-resolved fluorescence measurements. The fluorescence lifetimes measured during the curing process increase very fast near the gelation point. Investigations of the uncured system lead to the conclusion that two kinds of diffusion can be studied by using such probes: Stokes diffusion and diffusion into free volume.