Surface modification of low density polyethylene in a fluorine gas plasma

Abstract

Low density polyethylene was fluorinated in a glow discharge generated from a dilute mixture of fluorine in helium. The effects of pressure, flow rate, power and time of treatment have been examined. The fluorinated polymers were characterized using e.s.c.a. to identify the species present in the surface layer and to estimate the depth of fluorination. For typical plasma treatment of polyethylene films the fluorination depth was about 40 Å; a competition of ablation and ion-assisted etching processes with chemical reaction was observed. The depth of fluorination was increased to values above 60 Å by carrying out the reaction within a metal screen. The presence of the screen also reduced the reaction rate by about a factor of two. Other features of the treated polyethylene were determined by contact angle measurements, surface infra-red spectroscopy, solvent sorption and differential scanning calorimetry. Some early results of treatment of polyethylene powders in a fluidized bed reactor are also presented.