Research On Fire Characteristics And Flame Retardancy Of Traditional Wooden Structure

The traditional wooden structure of ancient architectural villages is a treasure of China’s ancient civilization,with its main structural form being a cross bucket structure,which has great ethnic characteristics and cultural value.However,traditional wooden structure buildings are mostly based on wooden component structures,with large fire loads and small fire separation distances.In addition,long-term exposure to wind and sun can result in extremely low moisture content and easy ignition of wood.Once a fire occurs,it is highly likely to cause rapid spread of the fire,causing devastating damage to traditional wooden structure villages.This article is based on the combustion characteristics of traditional wood structure building wood,and achieves efficient flame retardancy of wood by compounding two synergistic flame retardants GUP/APP/silicasol and guanidine/boric acid/silica sol synergistic flame retardants.Conduct combustion tests on traditional wood structure building wood components and flame retardant treated wood components through thermogravimetric analysis and cone calorimetry testing,and obtain combustion pyrolysis parameters to analyze the combustion performance of traditional wood structure building wood components and flame retardant treated wood components;Based on the traditional wood structure architectural model,which is a combustion parameter component,the fire spread law and influencing factors of traditional wood structure buildings are analyzed.The specific conclusions are as follows:(1)Selecting traditional wood structure building repair materials such as pimasson pine and Cryptomeria fortunei as research objects,thermogravimetric experiments were conducted at heating rates of 5k/min,10k/min,15k/mi,and 20k/min in the air atmosphere.Fitting equations for the main pyrolysis stages were established,and the main pyrolysis kinetic parameters of the two types of wood under different temperature rise rates were calculated.Chinese fir had higher thermal stability than pine.The fitting curves of the main pyrolysis stages of Chinese fir and pine samples are linear,proving the rationality of selecting g(a)=-ln(1-a)pyrolysis mechanism parameters.(2)Two transparent composite water-based flame retardants,GUP/APP/silica sol and guanidine/boric acid/silica sol synergistic flame retardants,were prepared.The flame retardancy and smoke suppression performance was better when the ratio of GUP/APP/silica sol was 2:1:2,determined through wood based flame retardancy parameter tests and cone calorimetry tests.The flame retardancy and smoke suppression performance was better when the ratio of guanidine phosphate/boron compounds was 2:3.The ignition time(TTI)of flame-retardant wood is extended by two times,and the fire growth index(FGI)is significantly reduced.The addition of silica sol as a composite flame retardant enhances the smoke suppression effect of wood and improves the strength of the treated wood.When the ratio of GUP/APP/silica sol was 2:1:1,the peak value of DTG of wood treated with flame retardancy decreased significantly,and the pyrolysis process was advanced.The residual carbon rate of wood was 26%,the residual carbon rate of blank material was 1.02%,the temperature of initial pyrolysis temperature and maximum weight loss rate of wood were advanced when the compound of dihydroguanidine phosphate/boron 2:3,and the carbon formation rate of flame retardant treatment group was 20.3%,respectively,which effectively promoted wood charcoal formation and reduced the mass loss of wood pyrolysis.(3)When the ratio of GUP/APP/silica sol is 2:1:1,the DTG peak of flame retardant treated wood is significantly reduced,and the pyrolysis process is advanced.The carbon residue rate of wood is 26%,and the carbon residue rate of blank group material is 1.02%.When the ratio of dihydroguanidine phosphate/boron compounds is2:3the initial temperature and maximum weight loss rate of wood pyrolysis are advanced.The carbon formation rate of the flame retardant treatment group is 20.3%,which effectively promotes wood carbonization.(4)A fire resistance test was conducted on the flame retardant front and rear partition boards under a small-scale fire source.The non flame retardant treated partition boards experienced flashover when the back temperature reached 300 ℃ at600 seconds.The temperature at the measuring points of different flame retardant treatment groups of flame retardant wood boards is over 100℃,and the fire resistance time of the samples treated with GUP/APP/silica sol flame retardant is 1.85 times that of the untreated wood.(5)Based on the parameters of wood pyrolysis combustion,a fire spread model for traditional wooden structure buildings was constructed.FDS is used to simulate the influence of different wind speed,fire separation distance and other factors on the fire spread process of adjacent wood structure building,and the fire spread characteristics,smoke movement,visibility,and temperature distribution of adjacent wood structure buildings are obtained.