Application of atmospheric air plasma for polyethylene powder modification

Summary form only given. Since polyethylene and other polymers are due to their apolar structure characterized with low wettability and adhesion, large effort has been concentrated on finding new low-cost and environment friendly methods for improvement of their surface characteristics. Majority of experiments has been focused on polymer foils and films modification, but in spite of frequent use of polymer powders in industry research dealing with modification of powders is less common, probably due to problems of polymer powder aggregation and difficulties with manipulation. This contribution presents results of experiments made for testing of dielectric barrier discharge (DBD) usability for polyethylene (PE) powder modification. Experiments were provided in DBD reactor. Glass plate separated rectangular brass electrodes, one of them grounded and the second one connected to a high-voltage transformer. The distance between the electrodes was 14 mm. The powder particles were gravity-fed in a continuous stream through the air plasma zone from a hopper at the top to a collecting bin at the bottom of the reactor. PE powder batch was repeatedly filled in the plasma reactor channel, number of transits through the plasma reactor was one of investigated parameters. The AC high voltage supply was used in experiments. The wettability of the PE powder was determined with a tensiometer from dynamic capillarity rising measurements according to the Washburn method. Experiments proved substantial rise of polyethylene powder capillarity with increasing number of powder batch transits through the reactor. Modified powder exhibited also very good adhesion to metal surfaces. Important aspect for practical application of plasma-modified powder is the time-stability of the modification effect. Aging tests showed only very slow powder capillarity decrease in time, therefore modification effect seems to be stable in time