SynopsisSeven new structurally different bismaleimides were synthesized and characterized by infrared and proton nuclear magnetic resonance spectroscopy. The chain of these polymer precursors was extended by incorporating amidized, imidized, and esterified 4-chloroformyl phthalic anhydride. The bismaleimides containing amide and imide linkages were prepared by a simple synthetic route based on the reaction of the monomaleamic acid derived from various aromatic diamines (1 mol) with 4-chloroformyl phthalic anhydride (0.5 mol) and subsequent cyclodehydration of the intermediate triamic acid. In addition, chain extended bismaleimides were prepared by reacting the monomaleamic acid derived from p-phenylenediamine with several dianhydrides such as p-phenylene bis(trimellitamide anhydride), p-phenylene bis(trime1litate anhydride), and bisphenol A bis(trimellitate anhydride). The differential thermal analysis scans of bismaleimides showed exotherms at 221-304°C associated with their polymerization reactions. The thermogravimetric analysis traces of polymers did not show a weight loss up to 351-393 and 344-372°C in N2 and air atmospheres, respectively. The anaerobic char yield of polymers at 8oo°C was 44-61%. These polymers can be used for fabrication of composites having improved properties.
SynopsisHeat-resistant polymers were obtained by thermal polymerization of several bismaleimides or their substituted derivatives. The chain of the polymer precursors was extended by incorporation of imidized benzophenone tetracarboxylic dianhydride between the maleimide rings in order to impart a degree of flexibility in the polymers. The bismaleimides and their corresponding tetraamic acids were characterized by infrared (IR) and proton nuclear magnetic resonance ('H-NMR) spectroscopy. The differential thermal analysis (DTA) thermograms of the monomers showed exotherms at 200-340°C attributed to the thermally induced polymerization reactions. The influence of different substituents in the maleic double bond on the curing temperature was investigated. The thermal stability of the cured resins was evaluated by thermogravimetric analysis (=A) and isothermal gravimetric analysis (IGA). They were stable up to 367-433°C both in nitrogen and air atmosphere and afforded 57768% char yield at 800°C under anaerobic conditions. The structure of the aromatic and aliphatic diamines utilized for imidization was correlated with the thermal stability of the cured resins. The bismaleimide derived from p-phenylenediamine gave the most heat-resistant resin because of its higher rigidity.
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