Curing and post-curing luminescence in an epoxy resin

Abstract

A spontaneous luminescence is reported when epoxy resin samples are heated in air. This phenomenon is very sensitive to the nature of the atmosphere. The same treatment in nitrogen leads to an extinction of the luminescence. The emission process is restored when samples are kept for a sufficient time in air. In order to better understand this phenomenon, we have investigated the luminescence of the elementary constituents of the epoxy (resin and hardener) when heated in air and nitrogen, as well as during resin curing in the same atmospheres. It appears that the emission process is linked with the presence of oxygen. Although the kinetics of the luminescence can differ depending on the nature of the sample (cured resin, resin during curing, liquid components), the emission spectra are the same during resin curing and upon heating of the cured resin and hardener. The emission spectrum of the base resin is different. It is concluded that the light results from a chemiluminescence process during oxidation.