When polymer materials are heated, irradiated with light, or mixed, some of the molecular structures can undergo changes that are a function of time. Infrared spectrophotometers (FTIR) provide an effective measurement method for tracking such changes, as they offer the ability to simultaneously track the changes of multiple absorption peaks.
When the main components of an epoxy-based adhesive are mixed with its hardener, they react and start hardening as a function of time, according to the process shown in the figure below. The changes in functional groups were investigated by measuring the hardening process at fixed intervals.
Hardening Process of Epoxy Polymer
Infrared Spectra of Epoxy Group and Hydroxyl Group
These charts show an overlay of peaks measured every 5 minutes. They show the hydroxyl group (3650 to 3140 cm-1) increasing as the epoxy group (925 to 899 cm-1) decreases.
