Rheokinetic studies and compressive response of high performance polybenzoxazine syntactic foams

Polybenzoxazines are finding increasing usage in demanding applications where high temperature stability is required, especially in the field of aerospace. In this work, thermally stable bisphenol F-based polybenzoxazine poly(BF-a)] syntactic foams containing varying volume fractions (30–60%) of hollow glass microballoons (HGMs) were prepared and their mechanical response in the quasi-static regime was established. The effect of introducing glass microballoons on the curing profile of benzoxazine resin was studied using both nonisothermal differential scanning calorimetry and rheometry. Temperature-sweep experiments were performed to arrive at the optimal processing window of the benzoxazine-glass microballoons formulations, particularly in terms of viscosity, gelation temperature, and time. Thermally accelerated ring-opening polymerization of the benzoxazine resin led to complete curing of the syntactic foam formulations, as assessed by calorimetric studies. The thermal degradation behavior of the poly(BF-a)/HGM was studied using thermogravimetric analysis. As expected, the density of the syntactic foam specimens decreased with increasing microballoon content. Maximal increase in the specific compressive properties of the poly(BF-a)/HGM samples was observed in formulations containing 40% volume fraction of glass microballoons. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47234.