Title: Plasma treatment of polyolefin powder-Process and application

Abstract

P olyethylene powder (PE) of average particle diameter of 160 µm was activated in a laboratory plasma reactor made from aluminum of volume 64 dm 3 at the pressure 100 Pa. Air and oxygen plasma were sustained with a microwave discharge powered by a pulsed magnetron source of power 1 kW. The evolution of powder wettability versus treatment time was measured using the Washburne method. Presence of polar groups on plasma treated powder was determined by X-ray Photoelectron Spectroscopy (XPS). Role of plasma penetration between particles was investigated. It was proved that certain degree of hydrophylization occurred up to 10 mm down under the upper layer of the powder. This penetration significantly contributes to the efficiency of powder treatment in large-scale applications. The penetration decreases with lowering the particles diameter and disappears for particles lower than some 20 µm. The plasma treated PE evidence adhesion enhancement to various materials. Plasma treated PE reaches joint strength with chrome and steel of 7.2 and 10.3 MPA respectively. The adhesion also resulted in improvement of mechanical properties of composite materials with PE matrix with glass or natural fibers. The tensile strength of samples prepared from plasma treated PE increased up to 74% in comparison with samples made from non treated PE. Based on the laboratory experiments an industrial scale set-up has been constructed. Some examples form industrial application of plasma treated powder will be presented.