The Formaldehyde Emission Source Of Surface Decorated Wood-Based Panels And Resin Synthesis Process

Surface decorated wood-based panels with paper impregnated thermosetting resins have drawn more and more public attention because of its favorable performance. A rapid progress has been obtained with the development of the panel furniture and the promotion of real estate and new rural construction. However, the problem of formaldehyde emission threatens indoor environment and human health seriously.This study analyzed the sources of formaldehyde emission by investigating the effect of fiber board base material and paper impregnated thermosetting resins on formaldehyde emission content respectively. The preparation technology and the impregnation process of urea-formaldehyde resin and melamine formaldehyde resin were optimized by orthogonal experiment and single factor experiment. The main purpose is to provide theoretical basis for producing finishing fiberboard with a lower formaldehyde emission content and a good performance. The conclusions can be summarized as follows:(1) The effect of the thickness and the limited level of formaldehyde releasing of the base material on formaldehyde emission content of the surface decorated wood-based panels with paper impregnated thermosetting resins was not significant; The effect of the formaldehyde emission content of paper impregnated thermosetting resins itself on the formaldehyde emission content of surface decorated wood-based panels was significant; The molar ratio of UF resin affected the formaldehyde emission content of the surface decorated wood-based panels to a great degree, and a low molar ratio of UF resin could reduce the formaldehyde emission content effectively.(2) It is reasonable to reduce the formaldehyde emission content of surface decorated wood-based panels by producing a low molar ratio of urea-formaldehyde resin; The formaldehyde emission content of surface decorated wood-based panels was much less than the limit of E1national standard when the molar ratio was1.4; Nevertheless, the physical and mechanical properties of the surface decorated wood-based panels with paper impregnated thermosetting resins, such as friction resistance ability, scratch resistance ability, acid and alkali corrosion resistance ability were decreased with a decreasing molar ratio of urea-formaldehyde resin.(3) There was an excellent ability of sealing formaldehyde emission from the impregnated papers, which could prevent most of the formaldehyde from releasing from the board. When the mole ratio was1.55, the formaldehyde emission of surface decorated wood-based panels with paper impregnated thermosetting resins from the paper impregnated thermosetting resins itself a part accounted for about56%, the formaldehyde emission from impregnated paper have a significant influence on formaldehyde emission of surface decorated wood-based panels.(4) The formaldehyde emission channel of MDF mainly includes the gaps between wood fiber, cracks between catheter and wood fiber, and the process of the preparation of the board. The principle for the paper impregnated thermosetting resins sealing the formaldehyde emission was the melt resin filled most cracks on the surface of the plate, and a dense layer would be formed after the solidification which would block the formaldehyde release channel. However, there were still some cracks and drills on the resin layer and some formaldehyde would release through them. At the same time, the paper impregnated thermosetting resins would also release an amount of formaldehyde by itself.(5) The factors of the effect on scratch resistance ability of finishing fiberboard surface deformation arranged from high significant to low were the molar ratio after joining the urea for the first time and the pH value during the acid reaction was processing. The factors of the effect on the resin storage period arranged from high significant to low were the temperature of the heat preservation and mole ratio; The factors of the effect on the formaldehyde emission arranged from high significant to low were the molar ratio and the pH value; The pH value of the melamine formaldehyde resin impregnated paper during the late period of the polycondensation reaction should not be very low.(6) The oven temperature in the first quarter during the impregnation process could be raise appropriately, which would make the core layer dipping urea-formaldehyde resin solidify completely, bring down the oven temperature in the second quarter, reduce the overall degree of procuring, and by this way, it would be easier to smooth the fiberboard during the late period of the melting, and improve the ability of the fouling resistance. For seasonal variations of temperature and humidity, manufacturers should pay more attention to the changes of the regional temperature and humidity, developing a stable process and making a suitable adjustment to different seasons on this base.