Numerical Simulation of Transient Surface Charging of Polymer Surface under DC Corona Considering Plasma Chemistry

In this paper, the transient process of negative DC corona generated with needle to plane electrode covered by polymer film is investigated by numerical simulation considering air plasma chemistry. The variation in plasma species in corona discharge and the transient process of charge accumulation on the film are examined. Moreover, the electric field and the mean electron energy distribution on the sample surface are discussed. Obtained results indicate that during the corona process, O
₂
⁺
, O
₄
⁺
and N
₄
⁺
are the dominant positive ions, O
₂
^-
and O are the main negative ion and the neutral particle, respectively. The charge accumulation region expands along the radial direction and the charge density increases gradually. In addition, the discharge channel shape is changed from column to cone with time, which is attributed to the electric field modification achieved by the accumulated charges. In 2000 ns, the mean electron energy distribution on the polymer surface varies between 2.1 and 5.8 eV and finally stabilizes to 3.7 eV, thus the electrons can overcome the barrier at gas-solid interface and become injected into the polymer bulk. It is suggested that the polymer surface charging transient is highly associated with the plasma behavior.