Determination of epoxide equivalent weight of epoxy resin using fourier transform near infrared spectroscopy

Abstract

The epoxide equivalent weight (EEW) of epoxy resin is the weight of resin in grams which contains one gram equivalent of epoxy groups. The EEW values must be accurately determined in order to calculate the exact amount of the hardener that will react with the epoxide group leading to cross-linked polymer of the desired properties. In this study, a method for determination of EEW values was developed using Fourier transform near infrared (FT-NIR) spectroscopy and partial least squares (PLS) regression to construct a prediction model. The predicted EEW values of unknown epoxy resins were compared with EEW values obtained from a reference method, based on titration of epoxy resin with hydrogen bromide generated in situ. The EEW values of both methods agreed well as shown by performance parameters RMSEC, RMSEP, and R values of 0.4265 g/eq, 0.4131 g/eq, and 0.9580, respectively. The newly developed method could be applied for routine analysis of EEW values of epoxy resin as it is simple, fast, accurate, non-destructive and environmental friendly.