Room-Temperature Phosphorescence Studies of Epoxy Resin Cured by an AromaticDiamine

摘要

The applicability of phosphorescence spectroscopy is investigated for curecharacterization of epoxy resin cured by an aromatic diamine. By using a time-resolved method to separate fluorescence from phosphorescence, the room-temperature phosphorescence (RTP) behavior of a commonly used curing agent, bis(p-aminophenyl) sulfone (DDS), is studied. RTP emission spectra with a maximum around 500 nm are obtained. Both RTP emission and excitation intensity increase very sharply with cure time due to the increase in the rigidity of the cured epoxy. They can be correlated to the extent of cure of epoxy, when properly calibrated. The triplet lifetime (tau sub T) obtained by monitoring RTP emission decay at 500 nm increases from zero to about 40 ms following cure at 160 deg C for 180 min. Correlation curves of tau sub T with the extent of cure and the glass transition temperature are also obtained. Thus, tau sub T provides a way to estimate the cure extent without the need to calibrate the RTP emission intensity. while these RTP characteristics cannot be used for in-situ cure monitoring, they can be used as a sensitive cure estimate technique in lightly cured prepregs for composites or after a cure cycle. jg p.2.