Properties Of Wood Treated With Nitrogen Phosphorus Flame Retardant

Wood, which is renewable natural material, is being applied in my many areas in human life due to its unique material performance and environmental friendly properties. However, wood application is wieldy limited for its flammability. During the shortage of available major diameter class wood, people turn to the use of available fast-growing wood resource. In general, the fast-growing wood shows the disadvantages of inferior material quality and low dimensional stability. The research on improvement of wood properties including flame resistance and physical properties becomes one of the important issues.In this paper fast-growing wood (China fir and poplar) was treated with environmental friendly nitrogen phosphorus compound flame retardants which were prepared from urea and phosphorus. The effects of flame retardant on properties of wood were characterized by thermal analysis, XRD and SEM. The results indicate as the followings:(1)With the concentration of different nitrogen phosphorus compound flame retardants APPUF rise, the weight percent gain of treated China fir increase. The weight percent gain of China fire show great influence on other properties of wood. The bulking coefficient, anti-swelling efficient, repellent water absorbability, anti-leaching and flame retardancy of treated China fir were improved according with the increase of weight percent gain.(2) The temperature of pyrolysis for China fir treated with different flame retardants APPUFs was decreased. During the stage of rapid weight loss, the apparent activation energy of treated China fir with APPUFs is 33.5-42.8kJ/mol which is lower than the value 63.6kJ/mol of untreated China fir with about 50%. The flame retardants changed the pyrolysis reaction mechanism mainly though catalyzing dehydration of wood and with released acids.(3)The increases of LOI values and residual char indicate the decrease of flammability of treated wood, suggesting effective flame retardancy of these FRs on wood. The LOI value of poplar treated with flame retardant PPU is 57.5%. SEM images of chars indicated that flame retardants treated wood maintained the wood fiber integrity afterburning and revealed the formation of a layer of nonflammable coating on surfaces of the burned wood.