木材保护与改性7.wood-polymer composite删减部分内容

Lignocellulosic–plasticcomposites木材-塑料复合材料Broadlymeaning：①PEG-treatedwood②Impreg③Compreg④Wood-vinylcomposites习惯上把第四种称为木塑复合材，即塑合木（WPC）主讲内容塑合木类木塑复合材混合复合型木塑复合材Chapter7WoodpolymercompositesLignocellulosic–plasticcomposites木材-塑料复合材料Broadlymeaning：①PEG-treatedwood②Impreg③Compreg④Wood-vinylcomposites习惯上把第四种称为木塑复合材，即塑合木（WPC）主讲内容塑合木类木塑复合材混合复合型木塑复合材Chapter7Woodpolymercomposites(1)DefinitionP209Impregnatingthewoodwithmonomer,thenpolymerizingunderγ-radiationorheat/initiator(catalyst),thusthemonomertransferintohomopolymerorgraftedonthewoodcellwall.(2)PerformancesComparedwithuntreatedwood,dimensionalstability,hardness,compressionstrength,abrasionresistanceandotherstrengthofWPCaregreatlyimproved,moreover,WPChavebeautifulappearanceandluster.木材保护学P209-230,woodpreservationandmodificationP56(3)Application：Buildingmaterials;furnitureandcraftwork;culturalandgymnasticmaterials.公共场所地板、木梭、线轴等、家具把手、乐器材、高尔夫球杆等。还有哪些地方可用？7.1ImpregnatedWPC7.2.1Materials7.2.1.1Suitablespecies7.2.1.2Monomers7.2.1.3Polymerization7.2.1.4Additives7.2.1.1Suitablespecies(1)Permeability:桦木属，槭木属、水青冈，栎木，水曲柳，桤木，杨木等(2)Custom：欧美：槭、桦日本：松、柏，表面WPC化7.2.1.2Monomers(1)Monomerincommonuse:苯乙烯（St）（styrene）甲基丙烯酸甲酯（MMA）（Methylmethacrylate）丙烯腈(AN)(acrylonitrile)不饱和聚酯(UPE)(UnsaturatedPolyester)丙烯类低聚体(PP)（propylene）苯乙烯是WPC开发初期常用的单体，但由于存在聚合所需能量大、聚合不完全等问题，现已不单独使用。苯乙烯（St）＋不饱和聚酯(UPE)：UPS苯乙烯（St）＋丙烯腈(AN):SAN苯乙烯（St）＋MMA:苯乙烯-MMA常用7.2.1.3PolymerizationChemicalCatalysts：偶氮二异丁腈（AIBN）等偶氮类引发剂过氧化苯甲酰（BPO）过氧化甲乙酮（MEKPO）等有机过氧化物引发剂对MMA：BPO或AIBN，要着色好常用AIBN对UPS：MEKPO或MEKPO+环烷酸钴引发剂加入量一般为树脂液的0.2～1%。Heat/Initiatorsinitiatingγ-radiationDyesCrosslinkingagent常用：过氧化物交联剂如：1,3-丁二稀，二甲基丙烯酸乙二醇酯，三甲基丙烯酸三羟甲基丙烷等Fireretardant7.2.1.4Additives7.2.2Manufacturingmethods(1)ImpregnationprocesswoodpreservationandmodificationP47,Fig2wood→putintothetreatingtankandweighted→Vacuumtreated→introducethemonomer(containingcatalyzeandotheradditives)→regainatmosphericpressure(orintroducedrynitrogen)→bringtheimpregnatedwoodout(2)Curingtheimpregnatedwood(→wrappedinaluminumfoil)→takeoutplacedinexplosion-proofoven,heatingorC060,radiation7.2.3Differencesbetweencatalyst-heatandγ-radiationprocessThedifferencesofcatalyst-heatandγ-radiationprocess(1)Thecatalyst-heatprocess(2)γ-radiationprocessThevirtuesanddefectsoftheabovementionedpolymerizingmethodsareshowninP212ofthetextbook.7.2.4Mattersneedingattention(1)Volatilizationofmonomer(2)shrinkanddistortafterpolymerization(3)AutoaccelerationBecauseoftheexothermicreactiontemperatureinthewood-monomercompositeincreases,andthehightemperaturedistillsthemoistureoutofthewoodcellwall.Thecellwallshrink,andthewoodalsoshrinksanddistorts.Remedialmeasure:machineuseγ-radiationpolymerizationReasonsforwoodshrinkanddistort①Species,influenceofwatermoistureonthepolymerizationexotherm.②monomer③Autoacceleration④initiator⑤crosslinking⑥additivessuchasDyes,fireretardants7.2.5InfluencingfactorsTheshortageofhighqualityhardwoodshasdrivenresearchersandwoodproductmanufacturerstoseekalternatives,lowercostresourcesforvalue-addedapplications.Toreachthisgoal,propertechnologiesareneededtoimprovespecificwoodqualityattributes(e.g.,dimensionalstability,durability,mechanicalproperties,andhardness)tomeetend-userequirements.Thebestapproachistocombinewoodwithpolymericmaterialstocreateanewcomposite.Therearetwocategoriesofwoodplasticcomposites(WPC).Oneispreparedbyimpregnatingsolidwoodwithamonomerorprepolymerandtheninsitupolymerization,whichisnamedimpregnatedWPCbyusintheformerclasses.InthesectionofimpregnatedWPC,weshouldknowthemainMonomersorprepolymersappliedintheproductionofimpregnatedWPC;polymerizationmethodsandtheiradvantagesanddisadvantagesinthemanufacture.impregnatedWPCAlthoughimpregnatedWPCarestrongerproductsthanwood,theconversionrateofpolymerizationhardlyreaches100%,themonomersareeasytovolatilizeandtheresiduemonomersorprepolymerstendtoleachfromtheproductandhaveanegativeimpactontheenvironment.Andmosteffortsonlydecreasedtherateofdimensionalchangeandtherateofswellingbutdidnotincreasedimensionalstability,becausethemonomersdidnotpenetratethecellwallsorreactwiththewood.TheotherWPCisplasticsreinforcedwithwoodfiberorparticles,whichwenamedMixwoodpolymercomposite.Plasticwastedisposalhasbeenrecognizedworldwideasanenvironmentalproblem.Recycledplasticsarereadilyavailablealmosteverywhere.Ifonecandevelopnewtechnologiesforthecost-effectiveutilizationofwasteplasticswithsolidwood,itcouldsolvetheaforementionedproblemsoflackofqualitywoodandplasticwastedisposal.MixedWPC7.3MixedWPCDef:Addingtheintensifiersuchaswoodparticles,fibersorpowdersintothermoplasticpolymers,andheatingtomixthewoodcomponentwiththemeltedplastics,thenthefinalproductscanbeobtainedfrompressmolding,spraymoldingorextrusionmolding.7.3.1MaterialsWoodymaterialsThermoplastichydrophilichydrophobicBadcompatibilityDifficulttomixuniformlyBadperformancesoftheproductPolyethylene(PE)Polypropylene(PP)Polyvinylchloride(PVC)Polystyrene(PS)Oilandwater?ThepropertiesofmixWPCdependsonmanyfactors,includingthepropertiesofthepolymerandfiller,thesizeandshapeoffiller(particulate,fibrous,etc.)