Kinetic analysis of long-lived luminescence in modified epoxy resins

Epoxy resins are widely known due to their excellent mechanical properties, high thermal stability and high chemical resistivity. Recently, a new class of the materials was synthesized containing carbazole derivatives. This modification does not influence superior mechanical properties of epoxy resins, but significantly improves their luminous capacity. Absorption spectra exhibit edge at about 355 nm. Excitation at shorter wavelengths causes intense photoluminescence (PL) in UV and VIS region even at room temperature. This paper presents long-lived luminescence properties of carbazole derivative modified epoxy resins. These processes are competitive to PL. Therefore in modified epoxy resins they are very weak. Phosphorescence decay (PD) and thermoluminescence (TL) experiments were performed using liquid nitrogen cooled CCD detection system. It allows measuring ultra-weak spectrally resolved luminescence in the range 200..1000 nm. The measurements were performed in a vacuum at different. temperatures from 80 to 330 K. Phosphorescence and thermoluminescence spectra exhibit several emission bands indicating various recombination mechanisms. The kinetics of PD and TL was analysed using a new numerical technique that allows determination of characteristic activation energies and deconvolution of three-dimensional spectra for individual processes.