Charge recombination luminescence from epoxy resins Part. 1. Correlation of luminescence with cure

The initial intensity of charge recombination luminescence (CRL) emitted by epoxy resins after brief periods of UV irradiation during cure has been me asured for a number of resins as a function of cure time. The results are c orrelated with measurements of extent of reaction of the epoxy groups, usin g near-IR spectroscopy, and with rheological measurements. They show that t he intensity of emission is directly related to the fractional conversion o f the epoxy groups, irrespective of the cure temperature, but that the emis sion only occurs when the conversion is high enough for the resin to be gla ssy. Attempts to increase the emission by adding aromatic amines failed. It is proposed that, for CRL to be observed, the resin must contain enough OH groups to stabilise the electron traps by solvation and be vitreous enough to prevent immediate recombination of electron-cation pairs. (C) 1999 Else vier Science Ltd. All rights reserved.