Thermally stable polyimide binders from aromatic dianhydrides and acetyl derivatives of aromatic diamines: Formation mechanism

Abstract

Abstract Polyimide resins based on dianhydrides of aromatic tetracarboxylic acids and acetyl derivatives of aromatic diamines have been developed for impregnating carbon fibers and glass cloth. Binder prepolymers are soluble in amide solvents and acetone and also form melts with a viscosity of 0.1–0.3 Pa · s at 250–300°C. The melt lifetime is 20–30 min. An increase in temperature leads to the formation of a crosslinked insoluble system of high thermal stability. The formation of polyimide binders was studied with the aid of IR and NMR spectroscopy. A mechanism of the reaction of aromatic dianhydrides with acylated amines is proposed. On the basis of polyimide binders from dianhydride of 3,3′,4,4′‐benzophenonetetracarboxylic acid and bis‐[4‐acetaminophenyl]‐sulfone, bis‐[4‐acetaminophenyl]‐ether, and N,N‐diacetyl‐p‐phenylene diamine, carbon fiber composites with good physico‐mechanical properties were obtained.