木材保护与改性4 wood fire retardance 02.ppt

*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,Chapter 4,Chemistry of fire,retardancy,4.1 Preface,4.2,The chemistry of,pyrolysis,and combustion,4.3 Mechanisms of fire,retardancy,4.4 Fire-retardant formulations,4.5 Future researches,4.1 Preface,Wood and its products are closely related to peoples lives.More and more people like to,decorate,their room with wood,and,woody buildings,draw more and more attentions.But as we known wood are combustible materials,which not only threat to peoples lives and possessions,but also limited their application areas.,With the increase of high buildings and large mansions,fire becomes the main trouble needing to be solved.,indoor decoration,building,gardening,and so on,The charming wood,in,The modern wooden building is very popular in most of the countries.,In 2000,90 percent of the,American,new villa(,别墅),was built up of wood.And,Among the 330,000 high rise residences,275,000 was built up of wood.,In,Canada,wood industry is the mainstay industry,the techniques of manufacture and installation are quite mature.,At present,more than half of the new houses in,Japan,are built up of wood or wood products.,Except for wooden houses,most of the public buildings such as factory,school,hotel,gymnasium and so on are built up of wood or wood products.,will you believe that wooden building can grow up in China in the future?,The chief criminal of fire,Wood,Wood is the criminal of fire.,Wooden building should be limited or discarded.,Is it right?,It,s a false and unadvisable idea.why?,Wood,Steel,cement,plastic,the extensively applied materials,the,only renewable material,In fact,wood especially large scale of wooden products are fireproof material.,Why?P108,In our mind,reinforced concrete is a kind of fireproof material,and strong enough to resist violent collision(,猛烈撞击,).,But reinforced concrete has a mortal defect(,致命的缺点,).,Would you tell me whats the fatal defect to reinforced concrete at higher temperature?,Reinforced concrete turns soft when undergoing high temperature.Normally,the strength of steel reduces by half when the temperature exceeded 300,C,and falls down when the temperature exceeded 500C.,Therefore,fire retarding is of the utmost importance.,Coffer(or safe),保险柜,:,制作材料？,金属,金属和木（竹）材,其它,1.,Is it necessary to preventing wood from fire,why?,2.According to your opinion,which kind of wood(assorted by their application areas)should be protected from fire?,3.From the pictures above,please tell me the most serious threats in a fire.,Questions,4.2,The chemistry of,pyrolysis,and combustion,Including four stages:,(1)The temperature of wood is improved under the heat.,(2)Wood gradually degrades and,pyrolyzes,the following material produces:,CO,2,CO,CH,4,CH,2,=,CH,2,R-CHO,R-CO,and so on,Tar(including phenol(,酚类,),aldehyde,(,醛类,),carbonyl chemicals(,羰基化合物,),Flammable gases,heat,Low molecular chemicals,And flammable gases,(3)Flammable gases,heat,Catch fire and combustion,There are four necessary conditions for the flammable combustion of wood:combustible gases,heat,oxygen and radical groups。,(4),Combustion,continues,Heat conducts to the adjacent wood,Combustion provide large amount of heat,Wood temperature improved,Pyrolysis,begins,then ignition,combustion,fire spread,and so on,Large amount of smoke also produced during the combustion of wood,the composition of the smoke is listed in the follows:,Combustible gases:CO,CH,4,H,2,CH,2,=,CH,2,R-CHO,R-CO,and so on,Noncombustible gases:CO,2,H,2,O,Tar:phenol,aldehyde,(,醛类,),carbonyl chemicals,Charcoal:combustible residue.,Pyroligneous,acid(,木醋液,):mainly formic acid(,蚁酸,),or acetic acid(,乙酸,),Some terms of combustion,Flame combustion(,有焰燃烧)：,luminous burning at the gas state.,木材进行发光的气相燃烧。,Smoulding,(,有焰燃烧)：,nonluminous,burning with smog.,木材燃烧时处于一种无可见光而有烟雾的燃烧。,Flameless combustion(,红热燃烧)：,aphlogistic,(,无焰,)combustion at a solid state.,木材处于固相状态 而没有火焰的燃烧，也叫无焰燃烧。,4.3 Mechanisms of fire,retardancy,Prevent the escape of volatile products by forming a glassy barrier.,Prevents oxygen from reaching the substrate,Insulates the wood surface from high temperatures,(1),Barrier theories(,障碍理论,),(2),Thermal theories(,热理论,),Fire-retardants may increase the thermal conductivity of wood to dissipate the heat from the surface faster than it is supplied by the igniting source;,Affect chemical and physical changes so that the heat is absorbed by the chemical.For example:chemicals content crystal water.,(3),Dilution by noncombustible gases theories(,不燃气体稀释理论,),Noncombustible gases released by the decomposition of the fire-retardant Chemicals,which dilute the combustion gases,and form a non flammable Gaseous mixture.,(4),Free radical trap theories(,自由基捕集理论,),Fire-retardant chemicals release free radical inhibitors at,pyrolytic,temperatures that interrupt the chain propagation mechanism of flammability.,CO,，,CO,2,，,H,2,O,，,HO,和其它成分,(1),HO,十,COCO,2,+H (2),H,十,O,2,HO,十,O (3),O+H,2,HO+H,(5),Increased charcoal/reduced volatiles theories(,炭量增加/挥发性气体减少理论,),书上,P118,反应式,Fire-retardant chemicals lower the temperature at which,pyrolysis,occurs,directing the degradation pathway toward more charcoal production and fewer volatiles.,(6),Reduce heat content of volatiles theories(,挥发物热含量下降理论,),This step is closely related with theories(5),that is theories(5)and(6)function together,resulting in more char,fewer volatiles and lower heat content of volatiles.,4.4 Protection of wood with fire-retardant,4.4.1 Treating methods,4.4.2 wood fire retardant,4.4.1 Treating methods,Physical methods,Reduce the ratio of combustible material by mixing wood,with Noncombustible materials.,For example:board made up of wood and cement,or fiberglass（,玻璃纤维）,plaster（,石膏）,or,asbestus,（,石棉）.,Cover the surface of wood with metal board or fireproof board.,Chemical methods:,The application of fire retardant.,Impregnate into the wood,Applied as paint or surface coatings,Two classes,Both of the two chemical methods have virtues and defects.,有机硼,有机硅,有机磷,-,氮,有机氮,有机磷,有机卤,氯、溴类,有机系,聚磷酸铵,红磷,氢氧化镁,氢氧化铝,无机系,4.4.2 wood fire retardant,木材阻燃剂应该满足一定条件。,P109,(1)Phosphors and its combinations（,磷及其化合物,）,Fire resistance of,Phosphors and its combinations are showed in the follows:,Reduce the temperature of,pyrolysis,;,Increase the production of char;,Reduce the production of combustible gases,；,Dilute the combustible gases,Monoammonium,and,diammonium,phosphates(,磷酸一铵盐和二铵盐),have,been the most effective fire retardants.,Organophosphorus,and polyphosphate,compounds(,有机磷酸盐及聚磷酸复合物),are also effective.,X,(,NH,4,),2,HPO,4,(,HPO,3,),x,+2xNH,3,+xH,2,O,(,HPO,3,),x,is,polyphosphate,(聚磷酸)，,which acts as a strong dehydrate agent,at higher temperature.Then,hastens,the forming of char,which protect the,inner wood from fire.,The efficiency of phosphorus compounds can be increased by the presence of other compounds such as nitrogen compounds that produce a synergistic effect（,协同效应）,P110.,P,N,synergistically,B,Br,抑制表面燃烧,The most effective fire retardants of phosphorus are the follows:,Phosphoric acid and urea（,磷酸合尿素）,Phosphoric acid and,diammonium,phosphates（,磷酸和磷酸氢二铵）,Phosphoric acid and melamine（,磷酸和三聚氢胺,）,(2)Halogen and its combinations（,卤素及其化合物）,Mechanisms,halogen hydride（,卤化氢）,can dilute the combustible gases.,At higher temperature,halogen escaped from the wood and,Cover the surface of wood for their high molecular weight.,Halogen can capture radicals from combustible materials and,reduce the concentrations of radicals,Defects of halogen fire retardants:moisture absorption,、,二噁英,Halogen applied in fire retardants:,NH,4,Cl，NH,4,Br，AlCl,3,6H,2,O，CaCl,2,2H,2,O，ZnCl,2,(3)Boron（,硼）,Borax and boric acid（,硼砂、硼酸）,the primary fire-retardant compounds,have low melting points and form glassy films on exposure to high temperature.,Borax and boric acid are always used together.,Defects of boron compounds,Lower solubility;,Easy to leach from wood and move to the surface,which influence the gluing,painting and other subsequent process.,(4)Leach-resistant,fire-retardants,Insoluble metallic salt complexes(,不溶的金属盐络合物),Others,Amino-resins(,氨基树脂):,UDFP,阻燃剂：,37%,甲醛溶液,调,pH,至,8,，加热至,80,加入尿素和双氰胺混合液溶解后冷却冷却到,35,时，慢慢加入磷酸得清亮阻燃剂溶液。,DBP,阻燃剂：,双氰胺、磷酸、硼酸制成。,FRW,阻燃剂：,高纯度磷酸脒基脲（,GUP,）、硼酸和少量助剂制成。,Examples,4.5 Future researches,Leach-resistant compounds,Improved fire-retardant treatments for panel products,Effective coating systems,Reduced smoke and toxicity,Basic mechanisms,4.6 Test methods,概 念,点燃温度（,Ignition Temperature,）,：,也称燃点温度。在规定的实验条件下，从材料中释放出的可燃性气体经外火焰点燃并燃烧一定时间的最低温度及氧指数。一般木材的点燃温度为,220-290,；,氧指数（,Critical Oxygen Index,）,：,在规定的实验条件下，试样在氮氧气流中，维持平稳燃烧所需最低氧气浓度。木材的氧指数为,27-30%,。,火焰传播指数（,Flame spread index,）：,指外火焰将材料一端点燃一定时间，火焰沿材料表面的蔓延速度与某种不燃材料、某种可燃材料表面或蔓延速度（标准样品）比较。,燃烧热值：,材料燃烧时释放的热量。一般木材的燃烧值为,17.6-20.0 MJ/kg,。,发烟等级：,材料燃烧时产生的烟雾对光遮蔽或光衰减程度所分的等级。一般木材的发言等级为,1-2,级。,Critical Oxygen Index(,极限氧指数,)Test,The oxygen index test measures,the minimum concentration of oxygen,in an oxygen-nitrogen mixture that will just support flaming combustion of a test specimen.Highly flammable materials have a low oxygen index,and less flammable materials have high values,。,氧指数代表材料的难燃性，其值越高，表明材料被点着所需的氧气越多，即越难点着。,测定氧指数对实验室筛选阻燃配方、初步确定材料的燃烧性能是一种简便、易行、重复性好的方法。国内标准：,GB/T 2406-93,。国外相同的标准有：,ISO4589.3,、美国材料学会标准、,ASTM D2863,、日本标准,JIS D1201,等。,There are several ways to test the efficiency of a fire retardant.The most common is to run TGA.,TGA involves weighing a finely ground sample and exposing it to a heated chamber in the presence of nitrogen.,Thermogravimetric,Analysis(TGA),DTA measures the amount of heat liberated or absorbed by a wood sample as it moves from one physical(transition state to another(such as melting or vaporization)or when it undergoes any chemical reaction.This heat is determined by,measuring the temperature differences between the sample and an inert reference,.DTA can be used to measure heat capacity(,热容,),provide kinetic data,and give information on transition temperatures.,Differential Thermal Analysis(DTA),Differential Scanning,Calorimetry,(DSC),DSC is similar to DTA,except,the actual differential heat flow is measured,when the sample and reference temperature are equal.In DSC,both the sample and reference are heated by separate heaters.If a temperature difference develops between the sample and,reference because of exothermic or endothermic reactions in the sample,the power input is adjusted to remove this difference.Thus,the temperature of the sample holder is always kept identical to that of the reference.,Building standards designed to control fire growth often require certain flame-spread ratings for various parts of a building.For code regulations,flame-spread ratings are determined by a 25-foot(,1,英尺,30.48,厘米,)tunnel test,which is an approved standard test method(ASTM E-84).For research,2-and 8-foot tunnel tests can also be done.All tunnel tests measure the surface flame spread of the wood,although each differs in the method of the exposure.A specimen is exposed to an ignition source,and the rate at which the flames travel to the end of the specimen is measured.,Tunnel Flame-Spread Tests,GBT 15442.3-1995,饰面型防火涂料防火性能分级及试验方法,-,隧道燃烧法,Cone Calorimeter,(,锥形量热仪,),，,原理：氧消耗原理。材料燃烧过程中每消耗,1g,氧，释放,13.1 KJ,热量，误差不大于,5%,。这种对应关系与材料种类和燃烧程度关系不大。,燃烧参数,（,1,）热释放参数：热释放速率、总热释放量、有效燃烧热,（,2,）点燃参数,（,3,）烟参数,（,4,）尾气及其毒性参数,（,5,）质量变化参数,林工科技楼,301,室,