Note: Thermal conductivity measurement of individual porous polyimide fibers using a modified wire-shape 3ω method

Porous polyimide fiber enjoys a good reputation as a high temperature resistant thermal insulation material in an aircraft-carrier, a spacecraft, and other military sophisticated products. Understanding its thermal conductivity is especially important for the design optimization and thermal management in these applications. In this study, a modified wire-shape 3ω method is developed to measure the thermal conductivity of individual porous polyimide fibers, utilizing a platinum layer heater/thermometer deposited along the circumferential direction of the fiber. The new method is first validated using a platinum wire with known thermophysical properties such as thermal conductivity at room temperature and then applied to porous polyimide fibers with diverse porosities. The thermal conductivity of porous polyimide fibers at room temperature is 0.06-0.15 W m^-1 K^-1, which reflects a good thermal insulation performance.