Fabrication of multifunctional polyimide foams with co-polymerized benzimidazole moieties for excellent thermal insulation and flame retardancy applications

Abstract

In this study, heterocyclic diamine 2-(4-aminophenyl)-5-aminobenzimidazole (APBIA) was employed as a co-polymerization component to improve the properties of polyimide foams (PIFs) which were synthesized from 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA) and 4,4′-diaminodiphenyl ether (ODA). The rheological behavior of polyester ammonium salt (PEAS) precursors was regulated by introducing APBIA moieties to the chain backbones, which affected the foaming behavior of PEAS and the microstructure of corresponding PIFs. Anisotropic porous structure was constructed with the help of microwave-assisted foaming strategy due to the directional growth of foam pores, which led to anisotropic mechanical and thermal insulation performance of resultant PIFs. PIFs demonstrated robust mechanical performance in the vertical direction (i.e., parallel to pore growth direction) and mechanical flexibility (compression response rate of 97.1∼99.0%) in the horizontal direction (i.e., perpendicular to the pore growth direction). The co-polymerized PIFs also presented excellent thermal insulation performance, with thermal conductivity ranging from 0.0266 to 0.0517 W/(m·K) within a temperature range of 25∼300°C. In addition, PIFs exhibited exceptional thermal stability and flame retardancy performance, which demonstrate a great potential for high-temperature thermal protection applications. To summarize, multifunctional PIFs with excellent mechanical, thermal insulation and flame retardancy were successfully prepared by adopting co-polymerization strategy and microwave-assisted foaming technique, which have promising applications in high-end engineering sectors.