Study On Plasma Surface Treatment Of Polyethylene Wood/Plastic Composites And Its Surface Properties

Low-pressure glow discharge of air plasma was adopted to treat the surface of Wood/Polyethylene composites. The change of surface treatment effect of Wood/Polyethylene composites with the discharge power and exposure time were investigated, and the stability and ageing of plasma treated composites was also studied.The relation of surface properties between discharge power and exposure time were investigated by surface wettability, surface morphology, surface chemical structure and surface adhesion ability. The surface wettability test showed that the contact angle decreased and surface free energe increased after plasma treatment, and the contribution of polor force is more than dispersion force for surface free energe. The results of SEM and AFM indicated that the surface roughness increased after plasma treatment and the roughness became obviously with the discharge power increase and exposure time prolong. The ATR-FTIR result showed that polar groups such as hydroxyl, carbonyl and carboxyl were introduced on the surface after plasma treatment, and the absorption peak of these polar groups strengthened with the discharge power increase and exposure time prolong. XPS analysis result indicated that the content of carbon element decreased while the content of oxygen element in the composition of composites surface element increased and the ratio of O/C increased, meanwhile a lot of carboxyl groups were formed on the surface, and the content of these carboxyl groups increased with the discharge power increase and exposure time prolong. The shear bonding strength test showed that the adhesion properties of composites improved effectively after plasma treatment and the bonding section showed cohesive failure or body damage of composites according with the difference of adhesives. The test of stability and ageing of plasma treated composites showed that with the storage time prolong after plasma treatment the surface wettability decreased, the conent of polar groups on surface decreased, the content of oxygen element and the ratio of O/C decreased, the content of-O-C=O group decreased till disappeared, but the shear bonding strength only showed a little decrease.