Manufacture and properties of Pinus kesiya flame retardant plywood

Pinus kesiya，which is widely used to make plywood，is commonly planted in Yunnan Province. To improve plywood properties（including mechanical and fire retardation properties）and promote safety because that the plywood panels without the fire retardation agents were easy to burn when those were used in interior decoration, the influence of flame retardation agents on the flame retardation agent impregnation rate of plywood，on mechanical properties，and on flame retardation of plywood panels was studied by means of orthogonal test. Results showed that when concentration of the flame retardation agent was 12 gkg-1 and the temperature was 100 C，flame retardation agent impregnation rates increased as the dipping time increased from 1 h to 5 h with rates of oven dry plywood higher than air dried. The impregnation rates were also different depending on the chemical composition of flame retardation agent and the moisture content of plywood（oven dry plywood and air dry plywood）. Additionally, as dipping time increased from 1 h to 5 h and when the flame retardation agent was FR-A（flame retardation agent A），mechanical properties（bonding strength）of plywood panels decreased from 0.97 to 0.73 MPa，the oxygen index（OI） increased from 41.89% to 64.88%, and the smoke density grade increased from 1.20 to 10.95. With flame retardation agent FR-B（flame retardation agent B），the mechanical properties of plywood panels decreased from 1.09 to 1.07 MPa，OI increased from 42.35% to 44.11%，and the smoke density grade increased from 10.57 to 17.95. Thus, flame retardation agents negatively influenced the mechanical properties of plywood panels，but this improved flame retardation properties making Pinus kesiya wood feasible for use in flame retardation plywood with further study necessary to lower the smoke density.［Ch，4 tab. 11 ref.］