Studies on structurally different benzoxazines based on diphenols and diamines: Kinetics of thermal degradation and TG-FTIR studies

• Aromatic diphenol and diamine based bisbenzoxazines were prepared and polymerized.
• Polybisbenzoxazines from quinol and p-phenylenediamine results in ladder structures.
• Meta diphenol and diamine based materials show intramolecular hydrogen bonding.
• Para oriented materials show higher thermal stability than meta oriented materials.
• Phenols are the major degradation products from diphenol based polybisbenzoxazines.

Structurally different bisbenzoxazines (QB, RB, pHBA-pd and mHBA-pd) are synthesized using quinol, resorcinol, p-phenylenediamine and m-phenylenediamine and are thermally cured. The thermal stability of the materials was studied using TGA. The plate like structure resulting from the interlinking of the ladders by intermolecular hydrogen bonding provides thermal stability to poly(pHBA-pd). The kinetics of thermal degradation is followed using Vyazovkin and Friedman methods. The diphenol based polybisbenzoxazines show higher apparent activation energy for thermal degradation (Ea-D) (PQB = 252–330 kJ/mol) than the diamine based polybisbenzoxazines (poly(pHBA-pd) = 98–188 kJ/mol). Aromatic amines are found to be released in considerable quantities from the diamine based polybisbenzoxazines whereas phenolics are released from diphenol based polybisbenzoxazines.

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