PBI fiber is one of the most mature applications of PBI. Due to its excellent flame retardancy (limited oxygen index LOI > 40), high-temperature resistance (strength remains almost unchanged at 371℃), and chemical corrosion resistance, PBI fiber is widely used in the manufacture of fire-fighting protective clothing, racing suits, spacesuit underwear, and aircraft fire-retardant layers. PBI fiber is often blended with para-aramid (such as Kevlar) to balance high strength and flame retardancy.

PBI is one of the core materials in high-temperature proton exchange membrane fuel cells (HT-PEMFC). PBI membranes doped with proton acids (such as phosphoric acid) exhibit extremely high proton conductivity under high-temperature (120-200℃) and anhydrous conditions, and possess excellent alcohol resistance, making them suitable for direct methanol fuel cells (DMFC) and hydrogen fuel cells. Furthermore, PBI shows promising application prospects as a non-fluorinated ion exchange membrane in vanadium redox flow batteries (VRFB), effectively addressing the vanadium ion permeation problem during battery operation.

PBI resin can be used to prepare high-performance composite materials, especially carbon fiber reinforced polybenzimidazole (CFRP-PBI), which has extremely high specific strength and specific modulus, making it suitable for aerospace structural components, radar radomes, etc. PBI can also be used as a high-performance adhesive for bonding metal materials such as titanium, beryllium, and stainless steel, with important applications in the aerospace field.

PBI membranes have unique advantages in high-temperature gas separation. Due to their rigid molecular chains and strong hydrogen bonding, PBI membranes have extremely high permeability to hydrogen (H₂) while exhibiting good barrier properties for large molecules such as carbon dioxide (CO₂), making them suitable for high-temperature H₂/CO₂ separation, natural gas purification, and other applications.