Synthesis and characterization of cardanol containing tetra-functional fluorene-based benzoxazine resin having two different oxazine ring structures

A new cardanol containing tetra-functional fluorene-based (t-BF-a-c) benzoxazine resins has been successfully synthesized via two-stage Mannich condensation reaction. The monomer contains simultaneous diamine- and bisphenol-type oxazine rings. The FTIR, H-1 and C-13 NMR tests were performed to confirm the structure of intermediates and t-BF-a-c benzoxazine. The rheological properties and curing behavior of the resin and thermal and thermomechanical properties of the corresponding polymer (poly (t-BF-a-c)) were evaluated by rheometer, differential scanning calorimeter, thermogravimetric analysis, and dynamic mechanical analyzer. The synthesized benzoxazine resin displays good processability and wide process window due to the incorporation of cardanol. Poly (t-BF-a-c) exhibits much higher glass transition temperature (373 degrees C) than corresponding bifunctional polybenzoxazines and better thermal stability than mono- and bi-functional cardanol-based polybenzoxazines. With the introduction of the flexible long alkyl chain of cardanol, the brittleness of fluorene-based polybenzoxazine is greatly modified without sacrificing thermal properties of the polymer.