Research On The Technology Of Impregnating And Densifying Plantation Wood And The Properties Of Treated Wood

After the implementation of Natural Forest Protection Project, develop plantation hasbecome the main method to solve the contradiction between timber supply and demand. Thedisadvantages of plantation such as low density and poor processing properties limit itsutilization. In order to improve plantation timber properties, modification is necessary. Overseaand domestic researchers as well as the author's experiments indicate that resin impregnationprocess is an effective approach to improve wood performance. It will provide a new way forthe high value-added utilization of plantation timber. It is also significant for expanding theplantation timber utilization fields.This paper begins with the synthesis technology of low molecular weight water solublephenol formaldehyde resin. The orthogonal experiment was applied to determine the optimalvacuum-pressure resin impregnation treatment parameters for plantation poplar timber. Poplarand Birch timber were treated according to the parameters. Then 100℃experiment werecarried out, and the drying schedule of each treated species were established separately. Themodern analysis methods were applied to examine the resin permeability and distribution in thewood. The change of wood crystallinity, chemical group and surface wettability caused byimpregnation treatment were also analyzed. After that, the physical and mechanical propertiesof treated wood, machining properties as well as finishing properties were systematicallyexamined and assessed. The novel plantation PF resin impregnation timber products weredeveloped. This paper comes up the conclusion as follows.1. The optimal vacuum-pressure resin impregnation treatment parameters of poplar timberwith large size are: resin concentration: 30%, vacuum keeping time: 60min, pressure: 1.0Mpa, pressure keeping time: 3 hours. Treat poplar and birch timber according to the aboveparameters, the weight increase rate of poplar and birch are 61.2% and 28.3 respectively.2. This paper studies the drying characteristic of treated wood and compare with the untreatedwood with the same moisture content by 100℃experiment. The drying schedules for thetreated wood were established. It is the innovation of this paper. The result shows thattreated wood has less serious drying defects and cost more time for drying than untreatedwood. The treated wood and untreated wood have similar drying characteristics. Thedrying schedule for birch is softer than poplar. After drying, little defects in treated woodwere detected. The treated wood has good drying quality.3. Resin permeability and distribution in wood after treatment were observed by SEM,cystallinity of treated wood was calculated by XRD and change of chemical group in wood after treatment was analyzed by FTIR. Result shows that PF resin not only impregnate intowood cell lumen and intercellular space, but also react with the some groups in cellulose,hemicelluloses and lignin. It is indicated that the PF resin impregnation treatment is acomplex physical and chemical process.4. The contact angle shows that treated wood has lower wettability than untreated wood,while after sanding the wood surface wettability increases. The order of the three chemicalreagents on wood surface wettability is: di-iodomethane (Good)＞formamide (Medium)＞distilled water (Bad).5. The physical and mechanical properties of treated wood show that all physical andmechanical properties except impact toughness have increased after treatment. The densityof poplar and birch wood increases by 78.8% and 24.2%, bending strength increases by113% and 61%, the modulus of elasticity increases by 56.7% and 30.3%, respectively.Poplar timber gets obvious improvements. Mechanism of dimensional stability lies in:resin fill in wood lumen and bulk; resin react with some groups in wood and form newchemical bonds, the absorbent group-Hydroxyl significantly reduce.6. The machining performance of treated wood shows that PF resin impregnation treatmenthas significant effects on machining performance of poplar wood. Treated wood has bettermachining performance than untreated wood. To birch wood, PF resin impregnationtreatment has no influence on its machining performance except for the cross cutting.Generally speaking, treated poplar wood has the best machining performance, while theuntreated poplar wood has worse machining performance.7. Three different types of paints were applied to finish both treated and untreated wood. Thecoating adhesion, coating abrasion and coating hardness were examined after finishing.The result shows that PF resin impregnation treatment has no negative effects on woodpaint finishing properties. Some species even has increased finishing properties.8. The development of novel products by treated wood shows that after PF resin impregnationtreatment, the treated wood is suitable to floor manufacturing. Treated poplar timber alsofits for door and window production. The products have good quality, beautiful appearanceas well as the low cost. It must have a promising market.