Study On Durability Of Bonding Joint For Plasma Treated Wood/Polyethylene Composites

The surface of wood/polyethylene (PE) composites was treated by low-pressure glow discharge of air plasma to study the change on the surface characteristics of the treated composites in different environments. The durability of bonding joint for plasma treated composites under different environments was also studied.The effect of different environment on the surface properties of plasma treated composites such as surface wettability, surface morphology, surface groups and elements was studied, and the durability of bonding joint of plasma treated composites was also investigated by bonding strength test. The contact angle test showed that the surface wettability of the treated composites increased, with the soaking and UV aging time extended, the contact angle increased firstly and then decreased; and with the heating time extended, the contact angle gradually increasing. The results of SEM indicated that the surface roughness of the treated composites which were placed in different environments all increased. The ATR-FTIR results showed that polar groups such as-OH, C-O and C=O were introduced on the surface after plasma treatment, the number of these polar groups decreased firstly and then increased with the soaking and UV aging time extended, however, the number of these polar groups decreased with the heating time extended. XPS analysis result indicated that the content of oxygen element in the composition of the treated composites surface element increased and the ratio of O/C increased, with the extension of the soaking and UV aging time, the content of oxygen element decreased firstly and then increased, the ratio of O/C decreased firstly and then increased, and with the extension of the heating time, the content of oxygen element gradually decreased, the ratio of O/C decreased. The shear bonding strength test showed that the adhesion properties of composites improved effectively after plasma treatment, with the extension of the soaking, heating and natural aging time, the shear bonding strength all decreased.The test results for the samples indicated that the environment shows a great influence on the surface properties of the treated wood/PE composites, and the greatest extent is soaking. Bonding is a phenomenon which occurs on the surface, the surface properties changes will affect the bongding strength changes, thus have a considerable effect on the durability of the bonding joint.