High efficiency synthesis of temperature resistant polyamideimide resin with branched structure using microreactor

Polyamideimide (PAI) resins have a wide range of applications. It is significant to explore novel and efficient synthesis methods. This paper describes a method for the rapid synthesis of branched PAIs in a microreactor using 4,4-methylenediphenyl diisocyanate (MDI) and 1,2,4-benzoic acid anhydride (TMA) as substrates. The isocyanate group reacts with the amide bond to build the branched structure. A high molar ratio of substrate helps to form more branched structures. High molar ratios also lead to high molecular weight products with narrow distribution, where the number average molecular weight of PAI-1.35 is as high as 1828.14 kg/mol and the molecular weight distribution index is only 1.09. Some oligomers are present in the products obtained at low molar ratios, which affect the mechanical and thermal properties of the products. Curing with epoxy resin can form a bulk structure and eliminate the effect of oligomers. The PAI films obtained after curing have excellent mechanical and thermal properties.