The Preparation Of Flame-retardant Wood By Coating And Immersion Method And Study On Its Char-forming Behavior

As a kind of renewable and easy processing material,wood is widely used in construction,furniture and other fields.However,as a flammable material,wood caused serious fire accidents once it was burned,so it was of great practical significance to treat wood with flame retardant.Nevertheless,the use of traditional organic flame retardants brought environmental problems as well as destroyed the aesthetic properties of wood itself.The purpose of this work was to develop the green,environmentally friendly and efficient flame retardant,through adjusting flame-retardant methods flexiblely,the flame-retardant wood was prepared by surface coating,impregnation and hot-pressing treatment,its charcoal-forming behavior was also studied.The main research work are as follows:(1)Sodium polysilicate(SPS)was prepared by nano silicon dioxide and sodium hydroxide,which was compounded with boric acid to prepare the green,transparent and efficient flame-retardant coatings.The limited oxygen index(LOI)was increased from 23.1%to 40.3%,the vertical burning test was reached V-0 according UL-94,and the total smoke release(TSP)was decreased by 36.0%after the weight gain of coating was 10wt.%.It was indicated that SPS promoted the formation of char and had great ability of char formation.(2)Calcium chloride and ammonium dihydrogen phosphate were used as precursors for the synthesis of carbonated apatite.The carbonated apatite(CAP)was in situ growth in the wood by ammonia fumigation.The treated wood had good fire resistance,the limiting oxygen index(LOI)was increased from 23.1%to 60.4%compared with the control wood,and the peak of heat release rate(pkHRR)was also decreased by 68%.It was indicated that the carbonated apatite formed the good thermal barrier.(3)The wood was delignificated with sodium chlorite,and a nanoporous scaffold was formed in the conduit.Phytic acid(PA)was impregnated into the nanoporous structure by impregnation method.The limiting oxygen index(LOI)was increased from 23.1%to 37.2%compared with the control wood,when the average weight gain of the wood was increased to 16wt.%.The total heat release(THR)was decreased from 49.6MJ/m2 to 14.2MJ/m2,which was decreased by 71.4%compared to the control wood.It was indicated that phytic acid(PA)catalyzed the carbonization of lignin and cellulose.The tensile strength and three-point bending strength of the fire-retardant wood was increased by 6 times and 8 times compared with that of the control wood,respectively.