Surface Treatment of Polymeric Fine Powders by CF4 Plasma in a Circulating Fluidized Bed Reactor

A low-pressure plasma surface treatment of polymeric powders was carried out in a circulating fluidized bed (CFB) reactor (10 mm-I.D. × 800 mm-high) with CF4 glow discharge. The effects of solid circulation rate, treatment time and radio frequency (rf) power of plasma on fluorination of high-density polyethylene (HDPE) powders have been determined. X-ray photoelectron spectroscopy (XPS) and the contact angle measurements were made to characterize the surfaces of powders. Solid holdup in the CFB plasma reactor mainly governs the stability of plasma glow and the surface property of the powders. Surface of HDPE powders is fluorinated into CHF-CH2, CHF-CHF and CF2 groups. The extent of fluorination increases up to 54% with the treatment time and rf power. The atomic percent of surface fluorine content increases with the composite parameters [(W/FM)t] and [(W/FM)t]/m down to 2,500 GJ·s/kg-gas and 19.8 GJ·s/kg-solid, respectively, thereafter it remains constant.