Gliding arc surface treatment of glass-fiber-reinforced polyester enhanced by ultrasonic irradiation

A gliding arc is a plasma generated between diverging electrodes and extended by a high speed gas flow. It can be operated in air at atmospheric pressure. It potentially enables selective chemical processing with high productivity, and is useful for adhesion improvement of material surfaces. The efficiency of such a plasma treatment at atmospheric pressure can be further improved by ultrasonic irradiation onto the surface during the treatment.

In the present work glass fiber reinforced polyester (GFRP) plates are treated using an atmospheric pressure gliding arc with and without ultrasonic irradiation to study adhesion improvement. The airflow at the arc ignition directed the GFRP surface at a grazing angle of approximately 30°. The ultrasonic waves of the frequency range between 20 and 40 kHz were introduced vertically to the GFRP surface through a cylindrical waveguide. It is found that ultrasonic irradiation reduced the OH rotational temperature of the gliding arc. The wettability of the GFRP surface was significantly improved by the plasma treatment without ultrasonic irradiation, and tended to improve furthermore at higher power to the plasma. Ultrasonic irradiation during the plasma treatment consistently improved the wettability. It is seen that polar functional groups were introduced at the surface by the gliding arc treatment, and that the treatment efficiency was enhanced by the ultrasonic irradiation, indicating that the adhesive property would be improved. TOF-SIMS ion images indicate that oxygen and nitrogen are uniformly attached at the treated surfaces with and without ultrasonic irradiation. The principal effect of the ultrasonic irradiation is attributed to enhanced oxidation during the plasma treatment.