Abstract
AbstractThe paper describes thermal and chemical cyclodehydration studies of bismaleamic acids prepared by reacting 4,4′‐diaminodiphenyl methane (DADPM), 4,4′‐diaminodiphenyl ether (DADPE), and 3,3′‐diaminodiphenyl sulfone (DDS) with maleic anhydride and 3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride. Thermal cyclisation was carried out by heating the bismaleamic acids at 120 – 140°C for 1 – 4 h. Chemical cyclisation was carried out by treating the bismaleamic acids with NaOAc/Ac2O to give bismaleimides BTM, BTE, and BTS, respectively. The products of thermal and chemical cyclisation were characterized by determination of acid number. Percentage conversion of bismaleamic acid to imide was found to be higher at higher temperatures for the same duration of thermal treatment. Elemental analysis and acid number indicated incomplete cyclisation of bismaleamic acid on thermal treatment. IR spectra of samples confirmed the disappearance of amide groups on cyclodehydration. In DSC traces of bismaleamic acids a broad endothermic peak due to imidization reaction was observed. Thermogravimetric analysis of uncured and isothermally cured samples was carried out in nitrogen atmosphere. Improvement in thermal stability was observed on curing.
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