Research On Isocyanate Impregnated Poplar Wood TVOC Release Characteristics And Optimization Of The Preparation Process

The promotion of the artificial fast-growing trees can effectively alleviate the contradiction between supply and demand in domestic timber market. However, fast-growing timber, such as poplar, has low density and poor stability, which limits its utilization. Domestic and foreign researchers’experiments indicate that resin impregnation process is an effective approach to improve wood performance. However, low-density wood treated with resin penetration will released more Volatile Organic Compounds than the untreated ones.In this paper, fast growing poplar wood was impregnated with isocyanate-acetone solution to manufacture strengthened wood. The significant factors which affected the WPG and TVOC emission of treated wood were analyzed and optimal production process was obtained on the premise of meeting the requirements of mechanical performance, processing costs and environmental performance. Meanwhile, the release characteristics and control mechanism of TVOC from the treated wood were explored.The main conclusions are summarized as follows:Improving concentration of isocyanate resin or increasing impregnation pressure or extending the pressing time can increase the WPG of poplar timber in varying degrees. Among the three factors, concentration of isocyanate resin is the most significant factor on the WPG, while impregnation pressure followed and pressing time thirdly.There can be more than 120 kinds of VOCs released from the treated poplar wood and 23 kinds of them can be stably detected. Among the VOC released from the treated poplar wood, the aromatic hydrocarbon has the largest proportion, followed by alkanes and terpene compounds.Resin concentration significantly affect the relese of TVOC of the treated wood. As the increase of resin concentration, the TVOC emissions of treated wood show downward after the first upward trend. Under the conditions of constant pressing time and different resin concentrations, TVOC changes inconsistent with the increasing impregnation pressure. Under the conditions of constant resin concentrations and different impregnation pressure, TVOC changes inconsistent with the extension of the pressing time.When the WPG of treated wood exceeds a certain value, the porosity of wood has significantly decreased, thereby the release of TVOC has been inhibited.With the extension of time, the TVOC of isocyanate treated wood decreases rapidly first, then decreases gradually, and finally reaches equilibrium.The BBD response surface analysis showed that the 3 parameters effect to three response values (WPG, MOE and TVOC emissions after 7 days) in descending order of the resin concentration, impregnation pressure and pressing time. When the mechanical properties, production costs and environmental performance were comprehensively considered, the optimal process parameters of strengthened poplar wood were the resin concentration 33.33%, pressing time 2.0h and pressure 1.0MPa. The feasibility and accuracy of optimal process parameters from the BBD experimental design were proved by the verified experiments.