The Waterborne Symposium

Abstract
Influence of Continuous Reactor B-Staging on Rheological and Thermomechanical Behavior of a Benzoxazine Matrix
Co-authors: Cecile Grubb, and John Misasi

The use of benzoxazine resin as a matrix in aerospace composite prepreg applications is desirable due to its inherent flame retardance and relatively low cost.  Prepreg performance properties before cure, such as matrix volume fraction, flow, and tack, are driven by the matrix prepolymer and are highly dependent on its level of conversion, or b-stage, as this impacts the viscosity during pre-impregnation.  This research sought to determine the impact of processing technique on matrix properties by comparing two b-staging methods: a traditional batch process and a continuous process using a twin-screw extruder.  The enthalpy of reaction and glass transition temperature were determined via differential scanning calorimetry and used to quantify the level of prepolymer b-stage from each process.  Prepolymer b-stage was then related to flow properties through study of viscosity profiles and gel points via parallel plate rheometry.  Finally, the effects of processing were analyzed in terms of cured thermomechanical behavior using dynamic mechanical analysis.  Significant reductions in the time to conversion were observed in materials processed using the continuous reactor.  Comparable rheological and thermomechanical properties were observed in material produced via both b-staging methods.