Study On Flame Retarding Urea-Formaldehyde Resin Adhesive And Its Application In The Plywood

Plywood is a kind of wood-based panels, which made of a number of odd pieces of wood fibers and formed by the hot pressing, curing and bonding. Plywood has many excellent properties, such as high specific strength, easiness to produce, maintaining the natural pattern and texture of wood, etc. There is a long history in the development of plywood, which has been dominant in the wood-based panel products. Plywood has been widely used in upholstery, furniture manufacturing, packaging and other fields, which is important for people’s life. The weakness of flammability of common plywood has limited its applications in many fields. Therefore, the study of flame-retarding plywood has important significance in practice.In this paper, the flame retarding urea-formaldehyde (UF) resin adhesive and its application in the plywood were studied. While the urea-formaldehyde resin adhesive was used as the base material, we improved its flame retarding efficiency and bonding effect, which had a good compositive performance of flame-retarding plywood. The main results were as followings:1. By the way of changing the composition of flame retardants in the system of UF resin adhesive and having the aid of vertical burning test on cotton canvas, some of the formula, which had a good flame-retarding efficiency, were selected. The results of mono factorial experiment showed that there were 14 kinds of the CP-based flame-retarding adhesive had good performance. The afterflame time and the afterglow time were Os, the char length were less than 150mm, the amount of smoke were scored less than 3.2. By studying the compatibility of flame retardants and UF resin adhesive and testing their storage stability, some flame retarding UF resin adhesives were chosen from the ones of step one determined. It was indicated that the best formula of one-component, two-component and three-component flame retarding UF resin adhesives were:10% CP/90% UF resin adhesive,5% CP/5% Al(OH)3/90% UF resin adhesive and 5% CP/2.5% Al2O3/2.5% Al(OH)3/90% UF resin adhesive respectively.3. The curing time and the pot life of the flame-retarding UF resin adhesive were studied. It was shown that the curing time was extended and the pot life fit the requirements. The order of the curing performance of flame-retarding UF resin adhesive was:CP/UF adhesive< CP/Al (OH) 3/Al203/UF adhesive< CP/Al (OH)3/UF adhesive.4. The fire-retarding mechanism of the flame-retarding UF resin adhesives on the process of porolysis was studied by TG and DTA thermal analysis techniques. It was certified that pure UF resin adhesive had a certain inflaming retarding effect on the wood fire. The extrapolated initial decomposition temperature of CP/UF resin adhesive, CP/Al (OH)3/UF resin adhesives and CP/Al (OH)3/A12O3/UF resin adhesive were all lower than the wood burning temperature, which meant that they had pretty flame retarding performance. CP/UF resin adhesive had the remarkable flaming retarding efficiency owing to the synergistic effects in the condensed phase and gas phase. There were also synergistic effects in CP/Al (OH)3/Al2O3/UF resin adhesive and CP/Al (OH)3/UF resin adhesive shown the good flame-retarding efficiency.5. The physical and chemical properties of the CP/UF resin adhesive, CP/ Al(OH)3/UF resin adhesives and CP/Al(OH)3/Al2O3/UF resin adhesives, which were applied in plywood, were studied. By the technological parameters:hot-pressing temperature 110℃, hot pressure 9 kg/cm2, hot pressing time 180 s, the flame-retarding plywood were pressed. The performance index of flame-retarding plywood was determined by the national standards for common plywood. It was indicated that the plywood pressed by CP/UF resin adhesive, CP/Al(OH)3/UF resin adhesives and CP/ Al(OH)3/Al2O3/UF resin adhesives all had the good flame-retarding efficiency and the formaldehyde gas emission amount of flame-retarding plywood was less than 5 mg/mL, which met the plywood of E2 level standard. The bonding strength of the flame-retarding plywood could reach the national standard with the pass rate of 100%. So they could be used as upholstery materials and furniture timber.