Effect of isomerism on mechanical and tribological properties of thermoplastic polyimide films

Abstract

Abstract A series of asymmetric polyimide (PI) films were prepared via polycondensation of 2,3,3′,4′-biphenyl-tetracarboxylic acid dianhydride (a-BPDA) with a pair of isomer 4,4′-oxydianiline (4,4′-ODA) and 3,4′-oxydianiline (3,4′-ODA). The effects of isomerism on the thermal stability, mechanical and tribological properties were systematically investigated. When molar fraction of 4,4′-ODA was increased in PI macromolecular chain, it had little significant effect on the nano-indentation hardness number and thermal stability. Furthermore, more of 4,4′-ODA monomer in PI increased the elongation at break but reduced the tensile strength, as well as it resulted in a lower coefficient of frictions(COFs). This evolution was related to macromolecular chain conformation caused by different monomer configurations. PI with a linear monomer (4,4′-ODA) resulted in a lower COFs and better wear-resistance.