Radio Frequency Heating Response Of Polyacrylonitrile (Pan) Films And Nanofiber Mats

The conversion of polyacrylonitrile (PAN) to carbonaceous structures is a complex but common processing step in the aerospace industry. Here, we show that this thermal stabilization process can occur based on the volumetric heating of PAN using radio frequency (RF) fields, in the 1-200 MHz range. Unlike many other polymers, neat PAN films show a surprisingly rapid RF heating response (5 degrees C/s at 103 MHz and 30 W power), without the need for any RF susceptor fillers. The RF response drops as the polymer oxidizes during heating and as the cyanide bond disappears to form a cyclic bond. Strangely, PAN nanofiber mats did not respond to RF fields. The measured AC conductivity and dielectric constant of fiber mats are lower (2.4 X 10(-4) S/m and 3.66, respectively, at 103 MHz) compared to 1.4 X 10(-2) S/m and 18.8 for PAN films. The dielectric properties are correlated with the bulk heating responses and stem from differences in morphology.