Surface modification of LDPE film by nanosecond-pulse dielectric barrier discharge at atmospheric pressure

Nanosecond-pulse dielectric barrier discharge (DBD) can provide non-thermal plasmas with extremely high energy and high density for achieving complicated physical and chemical reactions in surface treatment of polymers. In this paper, the surfaces of low density polyethylene (LDPE) films are modified by atmospheric-pressure non-thermal plasmas generated by nanosecond-pulse DBD^1,2. The DBD plasma is excited by a home-made nanosecond-pulse generator with a rising time about 70 ns, and a full width at half maximum of 200 ns. The surface water contact angle, surface free energy, surface roughness and surface chemical composition of the LDPE surfaces are measured by contact angle measurement, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) before and after treatment. Space charge distribution in LDPE before and after surface treated is estimated by pulsed electro-acoustic method (PEA). The aging characteristics are also studied by placing the treated materials in atmospheric air for a period of time. Experimental results show that as the treatment time increases, the contact angle decreases and the surface energy increases. Both the surface roughness and the oxygen-containing groups increase after the treatment. In addition, PEA measurements show that the plasma treatment can significantly suppress the space charge injection of the LDPE surface.