Study On Surface Strengthening Technology Of Fast-growing Fir And Its Adhering Capacity Of Coating

Wood enhancement is one of the method to improve the properties and the utilization ratio wood. In this study, the fast-growing fir was taken as the research object, and on the basis of compression, the method of low molecular weight phenolic(PF) resin impregnation and hot pressing compaction was used to strengthen the surface of the fir. By using the method of single factor experiment and regression analysis in the study, the relationship between compression rate and recovery rate, modulus of elasticity(MOE) and modulus of rupture(MOR) as well as the relationship between weight gain rate and impregnation pressure, impregnation time and resin solid content was obtained, and the compression process was determined. Meanwhile, through orthogonal experiment, the optimum dipping process was obtained by using range analysis and variance analysis. At the same time, the strengthening effect and coating adhesion properties of the enhance fir were researched, so that it can be better in the actual production of the application. The results were shown as follows:1) In the preliminary study, the impregnation effect of wet fast-growing fir can be improved by proper compression treatment. The MOE, MOR and the recovery rate of compressed wood decreased with the increasing of compression ratio. The recovery rate, MOE and MOR were reduce by 5.52%,3.31% and 5.16%, respectively, as the compression ratio was 23%. And the specimen appeared serious collapse when the rate was more than 23%, so 23% was chosen as the rate of the compression process.2) Through single factor experiment, it was found that was a quadratic curve relation between the weight gain rate and the dipping time, the impregnation pressure and the solid content:The relationship between the weight gain ratio and the pressure time was obtained: y=-0.55357x2+5.3324x+5.324, and the correlation coefficient R2=0.9976.The relationship between the weight gain ratio and the impregnation pressure was obtained:y=-0.74929x2+7.3327x+4.548, and the correlation coefficient R2=0.9992.The relationship between the weight gain ratio and the solid content was obtained: y=-1.3825x2+11.05x+2.7525, and the correlation coefficient R2=0.9976.3) The impregnation time, pressure and solid content all had significant influence on the impregnation effect, and the order was impregnation pressure> solid content> impregnation time, and the impregnation effect got the best as the impregnation time of 6 hours, the pressure of 0.8MPa and the solid content of 30%.4) Throught comparing the impregnation effect of compressed wood and untreated wood, the result showed the compression process was helpful to improve the impregnation effect of the specimen, and the weight gain rate of the specimens increased from 15.21% to 28.65% under the optimized impregnation process.5) The surface strengthening treatment had a positive effect on physical and mechanical properties of the fir. After treated, the density, MOE and MOR were increased by 28.53%, 82.28% and 86.99%, respectively. The hardness in radical section, tangential section and cross section were increased by the amplitude of 28.97%,47.82% and 44.53%, respectively. And the wear value reduced from 20.7 mg/100r to 9.8 mg/100r.6) The surface wettability of the treated wood was lower than that of the untreated wood, the contact angle increased from 23.6 degrees to 42.5 degrees, but it still belonged to partial wetting state, and the droplets could eventually penetrate into the treated wood. Moreover, by studying the paint film adhesion of samples that were respectively painted with waterborne wood lacquer and solvent coating, there was no obvious change in coating adhesion of treated and untreated specimens, and they were mainly in 1 stage, it indicated that the strengthening treatment had no significant effect on the adhesion properties of the coatings under the conditions of this experiment.