Effect of N2/O2 inclusion on polymer ablation and spallation phenomena from polyamide during thermal plasma irradiation

This paper reports enhancement effect of N₂/O₂ gas addition in thermal plasma irradiation on the spallation phenomena from polyamide-66 (PA66) specimens with water absorption. The polyamide materials are widely used, for example, in low-voltage circuit breakers and arcing horns as ablation material. In such devices, the polymer is often contacted with arc discharges to be ablated, which increases the arc current interruption ability of the circuit breakers. In our previous experiments, not only ablation but also spallation phenomena had been found to occur from PA66 specimens with water absorption by Ar thermal plasma irradiation. The present work was conducted to investigate effect of N₂/O₂ inclusion in the irradiating thermal plasma on the occurrence of spallation phenomena because the air circuit breaker was used in air. Relative oxygen admixture ratio to N₂ was changed from 0% to 100% with a fixed heat flux irradiated to PA66 specimens. Results indicated that O₂ inclusion effectively promotes the frequency of spallation particle ejection from PA66 specimen with 3 wt% water absorption.