Determination of epoxy equivalent weight of glycidyl ether based epoxides via near infrared spectroscopy

A method to quantify the epoxy equivalent weights (EEW) of glycidyl ether-based epoxides using near infrared spectroscopy (NIR) in combination with the Lambert-Beer law has been developed and validated by NMR and titration studies (ASTM D 1652). EEWs of a series of commercial aromatic epoxy prepolymers based on diglycidyl ether of bisphenol-A (DGEBA) and aliphatic epoxy prepolymers based on polypropylene glycol were determined via NIR. For instance, the commercial epoxide, Epon 828, was determined to possess an EEW of 186.44 ± 0.15 and 185.43 ± 2.55 via titration and NIR, respectively. Furthermore, the method was also validated to be applicable to determining EEW of rubber toughened epoxy prepolymers for two commercial materials. The results were supported and consistent with the EEW reported by the suppliers. NIR technique has been confirmed to be an excellent and rapid method to characterize epoxides as it is non-destructive and does not require the use of solvents or other chemicals.