EFFECT OF PLASMA TREATMENT ON THE TRIBOELECTRIC PROPERTIES OF POLYMERPOWDERS

Surfaces of fine polystyrene (PS) and polymethyl methacrylate (PMMA) p owders were modified by exposure to the downstream products of a nitro gen or oxygen microwave plasma. The effects of nitrogen and oxygen inc orporation in the powder surface were studied with emphasis on variati ons in the triboelectric properties of the powder. X-ray photoelectron spectroscopy was utilized to determine the changes in surface element al composition. After nitrogen plasma treatment, the C 1s peak shapes suggested the formation of amines in the case of PS, and the formation of imines and amides in the case of PMMA. Oxygen plasma treatment app ears to result in the formation of hydroxyl and carbonyl groups on the surfaces of both PS and PMMA. After treatment with a nitrogen or oxyg en plasma, the charge-to-mass ratio (Q/M) of PS and PMMA powders in co ntact with carrier particles was measured using the cage blowoff metho d. The surface charge density (Q/A) was calculated from Q/M. The Q/A o f nitrogen plasma-treated PS powder was seen to shift towards positive charge with small increases in the nitrogen concentration. The Q/A of oxygen plasma-treated PS powder initially shifted toward negative cha rge, but changed towards positive charge with higher oxygen concentrat ions. Plasma-treated PMMA powder showed a different behavior and the v ariation of Q/A on PMMA was much less than that of PS. Results suggest that triboelectrification of the polymer powder may be related to cha nges in the electrical surface states, and that nitrogen may act as a group V modifier within the PS surface.