Effect of Plasma Processing Rate on Poplar Veneer Surface and its Application in Plywood

Dielectric barrier discharge (DBD) plasma at atmospheric pressure in air was applied to a poplar veneer surface. Effects of plasma processing rate on surface morphology, chemical property, and surface wettability of the poplar veneer were investigated. The adhesion strength of urea formaldehyde (UF) glued plywood manufactured from the modified veneer was also studied. Atomic force microscopy (AFM), electron spin-resonance spectroscopy (ESR), X-ray photoelectron spectroscopy (XPS), contact angle tests, and shear strength tests were carried out. AFM indicated that the surface roughness increased after plasma treatment and was the maximum at a processing rate of 14 m/min. Both ESR and XPS tests showed more oxygen accumulation on the wood surface, forming various oxygen-containing chemical groups. Contact angle tests showed better wetting at a decreased plasma processing rate. Consequently, the adhesion strength of plywood increased after plasma treatment and showed higher strength at lower processing rates.