Cure characterization in bis(maleimide)/diallylbisphenol A resin by fluorescence, FT-IR, and UV-reflection spectroscopy

Curing bis(maleimide)/diallylbisphenol A (BMI/DABPA) results in the formation of a high-temperature thermoset resin. FT-IR, fluorescence, and UV-reflectance spectroscopy were used to investigate the cure behavior of this material under three different cure schedules. Fluorescence signals were quenched before curing due to the BMI component but increased and eventually leveled off as cure time increased. The largest fluorescence intensity increases occurred after 80% of the phenylmaleimide units were converted to phenylsuccinimide. Fluorescence signals were observed in both short-wavelength and long-wavelength regions. Model compound studies indicated that the phenolic portion of the BMI/DABPA resin has a higher quantum yield for fluorescence at a shorter wavelength than phenylsuccinimide derivatives. Therefore, fluorescence emission observed near 356 nm during curing is attributed to phenolic structures. FT-IR was used to quantify the extent of succinimide formation and to identify cross-linking processes which occurred during high temperature curing (250-260 degrees C). High-temperature curing processes were also identified by W-reflection spectroscopy. Various reaction pathways are discussed in terms of their consistency with the spectroscopic data.