Near infrared measurements of terminal epoxides in polymer resin systems. I. Analytical considerations

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Abstract
Terminal epoxides display a group specific near infrared absorption at 4532 cm−1. This combination tone is reasonably free of interferences and can be employed to measure oxirane ring concentrations for epoxy coating resin systems during synthesis and crosslinking. With the use of low signal‐to‐noise FTIR supported by computer data manipulation, chloroform solutions of five commercially available resins were analyzed for epoxide equivalent weight and correlated with results obtained by perchloric acid titrations. The near infrared technique displays linearity for epoxy concentrations of 3.6–20.7 meq/L. Similar results were obtained via a serial concentration study, indicating that the technique is not strongly affected by matrix effects.