Monitoring of reactive processing by remote mid infra-red spectroscopy

A novel experimental facility for remote mid infra-red (m.i.r.) spectroscopy has been assembled in our laboratory. We can conduct in situ real-time monitoring of practically any combination of processes and operating conditions, while, at the same time, enjoying the benefits of an unmatched wealth of molecular-level information contained in the m.i.r. range of the electromagnetic spectrum. The principal parts of our set-up are a host of optical components, gold-coated waveguides and a Fourier transform infra-red (FT i.r.) spectrophotometer. The signal generated in the remote mode was sharp, clear and reproducible, and the results were in every aspect as good as those obtained with conventional FT i.r. spectroscopy. The applicability of our remote m.i.r. set-up to in situ real-time monitoring of processing of reactive polymers was demonstrated by analysing the kinetics of cure of a multifunctional epoxy/amine formulation composed of diglycidylether of bisphenol-F (DGEBF) and 4,4′-methylene dianiline (MDA). A particularly interesting discovery was made concerning the necessary correction of the 'standard' epoxy peak at 915 cm^-1, which must be considered in order to preserve the reliability of kinetic results in the later stages of cure.