Bio-based poly(furfuryl alcohol) resin as a sustainable matrix alternative for prepregs

• Synthesis and characterization of thermoset prepreg resin made from furfuryl alcohol. • Application of B-staging procedures for tailored processing properties. • High-temperature curing leads to severe void formation and foam-like microstructure. • B-staging prior to final curing significantly mitigates porosity in C-stage. Despite their ecological superiority and competitive thermo-mechanical performance compared to petrochemical matrices, furan resins based on poly(furfuryl alcohol) (PFA) have so far played a minor role in composite applications. This is due to a demanding manufacturing process, which involves long curing cycles and specialized equipment for removing water from polycondensation to produce low-porosity parts. This work employs resin pre-curing (B-staging) to tailor PFA bio-resin properties for prepreg applications, while reducing the porosity in a fully cured state. A PFA prepolymer with a bio-content of 98 wt% was synthesized before heat treatments were applied for B-staging and final curing of the acid-catalyzed prepreg resin. The influences on viscosity, resin reactivity and chemistry, molecular weight, volatile separation, density, and porosity were investigated. It was found that an isothermal 120-minute B-staging procedure at 60 °C resulted in rheological behavior matching the processing properties of commercial, aerospace-grade epoxy prepregs. It was demonstrated that B-staging reduces volatile separation and associated void formation in the final curing step. Fully cured PFA samples with a porosity of less than 3 % could be produced employing short curing cycles. The findings advance the understanding of sustainable lightweight materials by tailoring PFA resins as potential polymer matrices for bio-prepregs.