木材保护与改性4woodfireretarda.ppt

Chapter4Chemistryoffireretardancy,4.1Preface4.2Thechemistryofpyrolysisandcombustion4.3Mechanismsoffireretardancy4.4Fire-retardantformulations4.5Futureresearches,4.1Preface,Woodanditsproductsarecloselyrelatedtopeopleslives.Moreandmorepeopleliketodecoratetheirroomwithwood,andwoodybuildingsdrawmoreandmoreattentions.Butasweknownwoodarecombustiblematerials,whichnotonlythreattopeopleslivesandpossessions,butalsolimitedtheirapplicationareas.Withtheincreaseofhighbuildingsandlargemansions,firebecomesthemaintroubleneedingtobesolved.,indoordecoration,building,gardening,andsoon,Thecharmingwood,in,Themodernwoodenbuildingisverypopularinmostofthecountries.,In2000,90percentoftheAmericannewvilla(别墅)wasbuiltupofwood.AndAmongthe330,000highriseresidences,275,000wasbuiltupofwood.,InCanada,woodindustryisthemainstayindustry,thetechniquesofmanufactureandinstallationarequitemature.,Atpresent,morethanhalfofthenewhousesinJapanarebuiltupofwoodorwoodproducts.,Exceptforwoodenhouses,mostofthepublicbuildingssuchasfactory,school,hotel,gymnasiumandsoonarebuiltupofwoodorwoodproducts.,willyoubelievethatwoodenbuildingcangrowupinChinainthefuture?,Thechiefcriminaloffire,Wood,Woodisthecriminaloffire.,Woodenbuildingshouldbelimitedordiscarded.,Isitright?,Itsafalseandunadvisableidea.why?,Wood,Steel,cement,plastic,theextensivelyappliedmaterials,theonlyrenewablematerial,Infact,woodespeciallylargescaleofwoodenproductsarefireproofmaterial.Why?P108,Inourmind,reinforcedconcreteisakindoffireproofmaterial,andstrongenoughtoresistviolentcollision(猛烈撞击).Butreinforcedconcretehasamortaldefect(致命的缺点).,Wouldyoutellmewhatsthefataldefecttoreinforcedconcreteathighertemperature?,Reinforcedconcreteturnssoftwhenundergoinghightemperature.Normally,thestrengthofsteelreducesbyhalfwhenthetemperatureexceeded300C,andfallsdownwhenthetemperatureexceeded500C.Therefore,fireretardingisoftheutmostimportance.,Coffer(orsafe)保险柜:制作材料？金属金属和木（竹）材其它,1.Isitnecessarytopreventingwoodfromfire,why?2.Accordingtoyouropinion,whichkindofwood(assortedbytheirapplicationareas)shouldbeprotectedfromfire?3.Fromthepicturesabove,pleasetellmethemostseriousthreatsinafire.,Questions,4.2Thechemistryofpyrolysisandcombustion,Includingfourstages:,(1)Thetemperatureofwoodisimprovedundertheheat.,(2)Woodgraduallydegradesandpyrolyzes,thefollowingmaterialproduces:CO2,CO,CH4,CH2=CH2,R-CHO,R-CO,andsoon,Tar(includingphenol(酚类),aldehyde(醛类),carbonylchemicals(羰基化合物),Flammablegases,heat,LowmolecularchemicalsAndflammablegases,(3)Flammablegases,heat,Catchfireandcombustion,Therearefournecessaryconditionsfortheflammablecombustionofwood:combustiblegases,heat,oxygenandradicalgroups。,(4)Combustioncontinues,Heatconductstotheadjacentwood,Combustionprovidelargeamountofheat,Woodtemperatureimproved,Pyrolysisbegins,thenignition,combustion,firespread,andsoon,Largeamountofsmokealsoproducedduringthecombustionofwood,thecompositionofthesmokeislistedinthefollows:,Combustiblegases:CO,CH4,H2,CH2=CH2,R-CHO,R-CO,andsoon,Noncombustiblegases:CO2,H2O,Tar:phenol,aldehyde(醛类),carbonylchemicals,Charcoal:combustibleresidue.,Pyroligneousacid(木醋液):mainlyformicacid(蚁酸)oraceticacid(乙酸),Sometermsofcombustion,Flamecombustion(有焰燃烧)：luminousburningatthegasstate.木材进行发光的气相燃烧。,Smoulding(有焰燃烧)：nonluminousburningwithsmog.木材燃烧时处于一种无可见光而有烟雾的燃烧。,Flamelesscombustion(红热燃烧)：aphlogistic(无焰)combustionatasolidstate.木材处于固相状态而没有火焰的燃烧，也叫无焰燃烧。,4.3Mechanismsoffireretardancy,Preventtheescapeofvolatileproductsbyformingaglassybarrier.PreventsoxygenfromreachingthesubstrateInsulatesthewoodsurfacefromhightemperatures,(1)Barriertheories(障碍理论),(2)Thermaltheories(热理论),Fire-retardantsmayincreasethethermalconductivityofwoodtodissipatetheheatfromthesurfacefasterthanitissuppliedbytheignitingsource;Affectchemicalandphysicalchangessothattheheatisabsorbedbythechemical.Forexample:chemicalscontentcrystalwater.,(3)Dilutionbynoncombustiblegasestheories(不燃气体稀释理论),Noncombustiblegasesreleasedbythedecompositionofthefire-retardantChemicals,whichdilutethecombustiongases,andformanonflammableGaseousmixture.,(4)Freeradicaltraptheories(自由基捕集理论),Fire-retardantchemicalsreleasefreeradicalinhibitorsatpyrolytictemperaturesthatinterruptthechainpropagationmechanismofflammability.,CO，CO2，H2O，HO和其它成分(1)HO十COCO2+H(2)H十O2HO十O(3)O+H2HO+H,(5)Increasedcharcoal/reducedvolatilestheories(炭量增加/挥发性气体减少理论)书上P118反应式,Fire-retardantchemicalslowerthetemperatureatwhichpyrolysisoccurs,directingthedegradationpathwaytowardmorecharcoalproductionandfewervolatiles.,(6)Reduceheatcontentofvolatilestheories(挥发物热含量下降理论),Thisstepiscloselyrelatedwiththeories(5),thatistheories(5)and(6)functiontogether,resultinginmorechar,fewervolatilesandlowerheatcontentofvolatiles.,4.4Protectionofwoodwithfire-retardant,4.4.1Treatingmethods4.4.2woodfireretardant,4.4.1Treatingmethods,Physicalmethods,ReducetheratioofcombustiblematerialbymixingwoodwithNoncombustiblematerials.Forexample:boardmadeupofwoodandcement,orfiberglass（玻璃纤维）,plaster（石膏）orasbestus（石棉）.,Coverthesurfaceofwoodwithmetalboardorfireproofboard.,Chemicalmethods:,Theapplicationoffireretardant.,Impregnateintothewood,Appliedaspaintorsurfacecoatings,Twoclasses,Bothofthetwochemicalmethodshavevirtuesanddefects.,4.4.2woodfireretardant,木材阻燃剂应该满足一定条件。P109,(1)Phosphorsanditscombinations（磷及其化合物）,FireresistanceofPhosphorsanditscombinationsareshowedinthefollows:,Reducethetemperatureofpyrolysis;,Increasetheproductionofchar;,Reducetheproductionofcombustiblegases；,Dilutethecombustiblegases,Monoammoniumanddiammoniumphosphates(磷酸一铵盐和二铵盐)havebeenthemosteffectivefireretardants.Organophosphorusandpolyphosphatecompounds(有机磷酸盐及聚磷酸复合物)arealsoeffective.,X(NH4)2HPO4(HPO3)x+2xNH3+xH2O,(HPO3)xispolyphosphate(聚磷酸)，whichactsasastrongdehydrateagentathighertemperature.Thenhastenstheformingofchar,whichprotecttheinnerwoodfromfire.,Theefficiencyofphosphoruscompoundscanbeincreasedbythepresenceofothercompoundssuchasnitrogencompoundsthatproduceasynergisticeffect（协同效应）P110.,P,N,synergistically,B,Br,抑制表面燃烧,Themosteffectivefireretardantsofphosphorusarethefollows:,Phosphoricacidandurea（磷酸合尿素）,Phosphoricacidanddiammoniumphosphates（磷酸和磷酸氢二铵）,Phosphoricacidandmelamine（磷酸和三聚氢胺）,(2)Halogenanditscombinations（卤素及其化合物）,Mechanisms,halogenhydride（卤化氢）candilutethecombustiblegases.,Athighertemperature,halogenescapedfromthewoodandCoverthesurfaceofwoodfortheirhighmolecularweight.,Halogencancaptureradicalsfromcombustiblematerialsandreducetheconcentrationsofradicals,Defectsofhalogenfireretardants:moistureabsorption、二噁英,Halogenappliedinfireretardants:,NH4Cl，NH4Br，AlCl36H2O，CaCl22H2O，ZnCl2,(3)Boron（硼）,Boraxandboricacid（硼砂、硼酸）,theprimaryfire-retardantcompounds,havelowmeltingpointsandformglassyfilmsonexposuretohightemperature.,Boraxandboricacidarealwaysusedtogether.,Defectsofboroncompounds,Lowersolubility;,Easytoleachfromwoodandmovetothesurface,whichinfluencethegluing,paintingandothersubsequentprocess.,(4)Leach-resistantfire-retardants,Insolublemetallicsaltcomplexes(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,4.5Futureresearches,Leach-resistantcompoundsImprovedfire-retardanttreatmentsforpanelproductsEffectivecoatingsystemsReducedsmokeandtoxicityBasicmechanisms,4.6Testmethods,概念,点燃温度（IgnitionTemperature）：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（CriticalOxygenIndex）：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（Flamespreadindex）：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17.6-20.0MJ/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。,CriticalOxygenIndex(极限氧指数)Test,Theoxygenindextestmeasurestheminimumconcentrationofoxygeninanoxygen-nitrogenmixturethatwilljustsupportflamingcombustionofatestspecimen.Highlyflammablematerialshavealowoxygenindex,andlessflammablematerialshavehighvalues。,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/T2406-93。国外相同的标准有：ISO4589.3、美国材料学会标准、ASTMD2863、日本标准JISD1201等。,Thereareseveralwaystotesttheefficiencyofafireretardant.ThemostcommonistorunTGA.TGAinvolvesweighingafinelygroundsampleandexposingittoaheatedchamberinthepresenceofnitrogen.,ThermogravimetricAnalysis(TGA),DTAmeasurestheamountofheatliberatedorabsorbedbyawoodsampleasitmovesfromonephysical(transitionstatetoanother(suchasmeltingorvaporization)orwhenitundergoesanychemicalreaction.Thisheatisdeterminedbymeasuringthetemperaturedifferencesbetweenthesampleandaninertreference.DTAcanbeusedtomeasureheatcapacity(热容),providekineticdata,andgiveinformationontransitiontemperatures.,DifferentialThermalAnalysis(DTA),DifferentialScanningCalorimetry(DSC),DSCissimilartoDTA,excepttheactualdifferentialheatflowismeasuredwhenthesampleandreferencetemp