Environmental Multi-ply Parquet With Low Resin Consumption

Multi-ply parquet emerges as the time required, which is made of precious broadleaf timber as overlaying and multi-plywood as substrate. In this paper, an effective approach to modify veneers by atmospheric pressure cold plasma treatme nt was developed. Plasma treatment can improve the quality of wood-based panels and the bond strength, reduce resin consumption. So the mechanism of the modification with the atmospheric pressure dielectric barrier discharge(DBD) plasma treatment was clarified, the surface wettability, microstructure, chemical characteristic and permeability were systematically analyzed. The paper can provide theoretical basis and practical experience for atmospheric pressure cold plasma modification technology used in the industrial production.The results are shown as following:1. The DBD plasma treatment can increase the bonding strength and reduce delamination of the multi-ply parquets. The date showed that the bonding strength was increased 27% for eucalyptus multi-ply parquet, 23% for poplar multi-ply parquet, 10% for masson multi-ply parquet and the delamination was decreased 75% for eucalyptus multi-ply parquet, 63% for poplar multi-ply parquet, 56% for masson multi-ply parquet. Optimized processing conditions were as follows: 4.5k W, 14m/min, 110g/m2 for poplar veneers, 4.5k W, 2m/min 100g/m2 for eucalyptus and 4.5k W, 2m/min, 120g/m2 for masson veneers.2. The bonding strength between oak veneer a nd poplar multi-ply parquet was improved along with the delamination decreased after oak veneer exposed to the DBD plasma. The bonding strength reached a maximum increase of 59% at 3k W, 8m/min, and the delamination reached a maximum decrease of 93.6% at 4.5k W, 2m/min.3. Obvious etching was observed on the wood transverse section after the DBD plasma treatment to different veneers, with a large number of cracks around the edge of cell wall. Meantime, the surface roughness increased after the DBD plasma treatment to different fibers. So the fiber had a great specific surface area. It is beneficial to increase the contact area between the veneer and adhesive, and increase the bonding strength.4. The DBD plasma treatment can decrease the contact angle on the surface of different veneers, and increase surface free energy of veneer. The initial angle and balance angle were decreased 78.2% and 104.7% for eucalyptus veneer at 4.5k W, 2m/min, 12.2% and 36.9% for poplar veneer at 4.5k W, 8m/min, 16.1% and 16.9% for masson veneer at 4.5k W, 2m/min.5. More free radicals on surface of different veneers could be generated by The DBD plasma treatment. The XPS showed that: The DBD plasma treatment increased the O/C atomic ratio of the wood surface, and the content of C-H and C-C of every veneer decreased, the content of-C-O,-C=O and –COO of poplar veneer increased, the content of-C-O and –COO of eucalyptus veneer increased, the content of –C=O、–COO of masson veneer increased. These results show that a large number of oxygen content groups were generated on veneer surface with treatment.6. The permeability of the urea- formaldehyde resin enhanced with the DBD plasma treatment. It was observed on the poplar and eucalyptus veneers. The effective permeability of poplar veneer was increased 37.7% with the average penetration up to 2.6 times and the effective permeability of eucalyptus veneer was up to 2.1 times with the average penetration increased 54.7%.