Surface modification of polyimide using dielectric barrier discharge treatment

We report on a novel method for the surface modification of polymers by dir ect exposure to a dielectric barrier discharge (DBD) at atmospheric pressur e and room temperature. The polymer under treatment is located directly on the grounded electrode and serves at the same time as the discharge barrier . So far DBD treatment of the unfilled and Al2O3-filled commercially availa ble polyimide foils have been investigated as a function of specific discha rge energy. The morphological effects of the DBD treatment have been analys ed by optical microscopy, SEM, AFM, and chromatic coding distance measureme nt while XPS was used for analysis of the chemical surface composition. The results can be summarised as follows: Firstly, the etching rate of the pol yimide (PI) surface by DBD in air is rather high leading to a pronounced ro ughening within some tens of seconds. Secondly, the attack is dependent on whether the polyimide contains a filler, which is added to improve the ther mal conductivity of the material. In this case the etching lays bare the gr ains of the filler but is spatially rather uniform. The surface roughening increases the bond strength to coating layers. Finally, in the unfilled mat erial crater-like structures are observed which are attributed to the repet itive ignition of discharge filaments in the same location. (C) 2001 Elsevi er Science BN. All rights reserved.