Development of fundamental understanding of the cure kinetics of benzoxazine epoxy blends
Maffe, Adam Paul
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This study attempts to bridge the gap between the current fundamental understanding of benzoxazines on the monomer level and their macro scale thermo-mechanical properties. Bisphenol-A based benzoxazine (Bz) was blended with di- and tri-functional epoxies to reduce viscosity for processing, and their resulting thermal and mechanical properties were characterized. Additionally, the formation of inter-molecular and intra-molecular hydrogen bonds was investigated within a Bz-epoxy two component system. Activation energy, heat of reaction, degradation temperature, hydrogen bonding characterization and thermo-mechanical characterization were studied using a differential scanning calorimeter, dynamic mechanical analyzer, thermogravimetric analysis, Fourier transform infrared spectroscopy and quasistatic tensile testing. Preliminary results show a synergistic increase in Tg of the blends, for both di- and tri-funcitonal epoxy blends. Surprisingly, while the two components exhibit Tg’s of ~ 150-170 oC, the blended systems consistently exhibited a Tg in the range of 210-250 oC. This work aims to expand upon thermal and mechanical characterization data generated by our collaborator Ehsan Barjasteh for the benzoxazine – di-functional epoxy system, as well as explore a new benzoxazine – tri-functional epoxy-based system. Our underlying motivations in this study are to identify the origins of the synergistic increase in Tg upon blending through various thermo-mechanical characterization methods and in-situ FT-IR analysis of cure kinetics, as well as identifying the compositions and functionality which exhibit the most desirable combination of thermal and mechanical properties.