Effects of Dielectric Barrier Discharge Plasma Treatments on the Performance of Poplar Plywood Produced with UF Resins of Different Molar Ratios

Hui Wang, Zhigang Duan, Feng Wang, Hongyan Wang, Guanben Du

Abstract


Poplar veneers were treated with dielectric barrier discharge (DBD) plasma at atmospheric pressure, and the effects on the veneer surface feature were explored. The bonding strength of poplar plywood glued with different urea-formaldehyde resins of varying molar ratios was also investigated. The wettability and resin penetration of the veneer treated with DBD plasma were dramatically improved, especially for the UF resin with a higher formaldehyde to urea (F/U) molar ratio. The apparent contact angle of the veneer-treated plywood decreased and the resin penetration content increased as well. The bonding strength of the plywood increased in different degrees, and the wet bonding strength in particular sharply increased; when the F/U molar ratio was 1.3, the strength was improved by 138.2%. However, when the F/U molar ratio increased, the wet bonding strength improvement declined. The veneer surface image before and after the DBD treatment was invested via scanning electron microscopy, the surface was rougher and looser, which was beneficial for resin penetration. These all indicated that the balance between the characteristics of the resin and the penetration of the veneer surface is critical for an improvement in the bonding strength of plywood.

Keywords


Plasma treatment; UF resins; Poplar plywood; Penetration behaviors

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