Experimental study on surface modification of PET films under bipolar nanosecond-pulse dielectric barrier discharge in atmospheric air

• Published in: Applied surface science 2014-09, Vol.313, p.53-59
• Main Authors: Liu, Yunfei, Su, Chunqiang, Ren, Xiang, Fan, Chuan, Zhou, Wenwu, Wang, Feng, Ding, Weidong
• Format: Article
• Language: English
• Subjects: Atmospherics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Dielectric barrier discharge; Dielectric properties; Exact sciences and technology; Insulation; Nanostructure; PET film; Physics; Polyethylene terephthalates; Scanning electron microscopy; Surface modification; X-ray photoelectron spectroscopy
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2014.05.129

•Homogeneous DBD is generated under bipolar nanosecond pulse in atmospheric air.•Effects of surface modification under homogeneous DBD are discussed.•Dielectric properties of the PET films are fully studied from relative dielectric constant ɛr, dielectric loss tangent tanδ and breakdown voltages Vb.•Oxygen-containing polar groups are considered to be the most essential reason for dielectric property changes. Dielectric barrier discharge (DBD) is widely used for surface modification of polymer films. In this paper, DBD characteristics under bipolar repetitive frequency nanosecond pulse in atmospheric air are studied and surface properties of polyethylene terephthalate films under homogeneous DBD and filamentary DBD modification are compared through scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and dielectric test equipment. It is found that the discharge is homogeneous when gap spacing d is less than 1.2mm and filamentary when d is within the range of 3.0mm to 5.8mm. SEM pictures reveal that films under homogeneous DBD present a smooth surface while intensive “gully-like” etches appear on the surface of the films under filamentary DBD, which can result in local insulation defects and is disadvantageous to surface modification. It is found from the XPS analysis that a number of oxygen-containing polar groups are introduced onto the surface of the film modified by homogeneous DBD compared with the untreated one. Experimental results for dielectric properties indicate that the three parameters: relative dielectric constant ɛr, dielectric loss tangent tanδ and breakdown voltages Vb are all changed in different degree after surface modification. And possible reason for the phenomenon is discussed.