Synthesis and properties of new polyimide foams from foaming compositions with flexible segments of aliphatic diamine

Abstract

New foaming prepolymer compositions based on 4,4′‐oxydiphthalic anhydride, 4,4′‐diaminodiphenyl ether, 1,6‐hexamethylenediamine (HMDA), and a surfactant were synthesized. Polyimide (PI) foams containing from 0 to 40 mol% HMDA were prepared. The possibility of controlling the pore sizes in a foam material by selecting different fractions (250–400 μm) of particles of the powdered foam composition for heat treatment was shown. Scanning electron microscopy studies of morphology of the synthesized PI foams (PIFs) showed that all foams exhibited open cellular structures with pore diameters ranging from 50 to 500 μm. The influence of the components of the foaming composition (surfactant and aliphatic diamine) on the structure, thermal, and mechanical properties of the resulting PIFs was traced. The samples of PIFs containing 20% and 30% HMDA were elastic (the corresponding stress–strain curves were almost linear up to the 30% deformation) and able to restore their shape after removing the load. The resulting foams exhibited high thermal stability (the onset of weight loss was observed in the 470–500°C range). It was revealed that the synthesized PIF compositions were incombustible in an open flame. Due to their high heat resistance and nonflammability, the obtained PIFs can be used for thermal insulation applications in the aerospace, transport, construction, and microelectronics industries.Highlights New, lightweight, flexible, and nonflammable PIFs have been synthesized. The HMDA additive imparts elasticity to PIFs. The introduction of a surfactant (KT‐6) makes the PIF homogeneous.