Formation of Electro-Conductive Part on Polymeric Material Surface by CO₂ Laser Irradiation

In this study, a method to directly form an electrically conductive layer on the surface of polymeric material by using infrared laser irradiation was investigated. Polyacrylonitrile, which was shaped into a small disk 20 mm in diameter and 5 mm thick, was used as a test specimen. The conditions for pyrolysis were obtained by referencing the conditions for commercial carbon fiber. First, the specimen was processed in air at a relatively low temperature (around 250°C) for the stabilization treatment (i.e., fireproofing), then its surface was heated at a higher temperature (above 1000°C) for the carbonization treatment (i.e., graphitizing). Both an infrared furnace and a carbon dioxide laser were used as heating devices to find optimal conditions. Property changes in the material due to the thermal treatment were measured using Fourier transform infrared spectroscopy, and the electrical conductivity of the carbonized surface was measured using a four-probe method. The results showed that an electrical conductivity of 11.4 S/cm (siemens per centimeter) was achieved with a laser intensity of 8.6 W/cm² for 5 min for the stabilization, and a laser intensity of 34 W/cm² for 10 s for the carbonization.