PLASMA SURFACE TREATMENT OF WOOD POWDER/POLYETHYLENE COMPOSITES-EFFECT OF TREATMENT TIME ON SURFACE CHARACTERISTICS OF THE COMPOSITES

Low-pressure glow discharge of air plasma was used to increase the wettability of wood/PE composites in order to improve their adhesion properties. The changes in surface properties of the composites treated under plasma were studied by contact angle measurements, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. Contact angle were measured at different exposure times for a series of test liquids, and the results showed that the contact angle decreased after being plasma treated under different exposure time, which meant that the surface wettability of the composites was improved significantly. The FTIR analysis results showed that polar groups such as hydroxyl, carbonyl and carboxyl were formed on the surface of the composites treated under plasma. And the generation of these polar groups was benefit of improving the wettability and adhesion capability of wood/PE composites. XPS analysis results indicated that the content of oxygen element in the composition of surface element for wood/PE composites increased after plasma treating, and it reached a balance in a short time, meanwhile a lot of carboxyl groups were formed.