聚合物化學(xué)翻譯 第八章課件

Chapter8PolymerDegradation

indefinitely：無止境的;無限期地

exposure：暴露

desirableproperties:預(yù)期的性質(zhì)P139-1

Organicpolymersarenotindefinitelystableunderallconditions.Inparticularinfiresoronexposuretooutdoorconditionsespeciallysunlight,theywilltendtoundergoreactionsthatleadtoalossoftheirdesirableproperties.INTRODUCTION有機的聚合物并非在所有條件下無限期的穩(wěn)定存在。特別是著火或暴露在戶外尤其是陽光下，它們傾向于發(fā)生反應(yīng)導(dǎo)致失去預(yù)期的性質(zhì)。degradation:降解

weathering：氣候浸蝕

minimising：減少Thisisknownasdegradationandofteninvolvesbothreactionwithoxygenandreductioninmolarmass.Polymerdegradationbothinfiresandonweathering,togetherwithtechniquesforminimisingthedamagecausedbytheseconditionsarethesubjectsofthischapter.這被稱為降解并常常伴隨有與氧的反應(yīng)和摩爾質(zhì)量的降低。在燃燒和氣候浸蝕兩種作用下，聚合物降解及減少由這些條件引起危害的技術(shù)是本章的主題。ascloselyaspossible盡可能近期

adepartmentstore:商店stack：堆放

vicinity：附近P139-2Thesewerechosentorepresentascloselyaspossibleafirethathadoccurredinadepartmentstoreandwhichhadresultedin10deaths.Theitemswerestacked,astheyhadbeeninthestore,andignited.Oneminuteafterignition,atemperatureof1000℃wasrecordinthestack;theconcentrationofoxygenfellrapidlyinthevicinityofthestack,reaching6.5%after2minutesandafinallevelof3%duringtheperiodofsustainedcombustion.挑選盡可能近期發(fā)生在一處百貨商店的一場火災(zāi)為代表，它致使10人喪生。物品被堆放在一起，當(dāng)它們貯藏時被點燃了。點燃后一分鐘，在火堆中記錄到1000℃的溫度，在火堆的附近氧氣濃度迅速降低，2分鐘后達到6.5%，最終維持燃燒期間達到3%的水平。illustrates：說明

unique：獨一無二的P139-3Thisexampleillustratestherangeofoxygenconcentrationsandthekindoftemperaturethatcanoccurinarealfire,butthisisonlyanillustration.Therearenostandardconditionsforrealfires,sinceeachfireisauniquephysico-chemicalevent.這個例子表明發(fā)生真實火災(zāi)中氧氣濃度的范圍和溫度，但這僅僅是一個例子。對于真實火災(zāi)不存在標(biāo)準(zhǔn)的條件，因為每一次燃燒都是一個獨一無二的物理化學(xué)事件。Firebrigades：火災(zāi)救援隊P140-1Withtheincreasinguseofpolymersinboththehomeandtheworkplace,thereseemstohavebeenachangeinthenatureoffires.Firebrigadesnowreportfiresthatareshorterandmoreintensethanpreviously;thereisalsomuchmoresmokeandsignificantlygreateramountsoftoxicgases.Allofthesearisefromthenatureofthepolymersbeingusedineverydaylife.隨著聚合物在家居和工作單位中使用的增加，火災(zāi)的本性似乎存在某種改變?，F(xiàn)在火災(zāi)救援隊報告火災(zāi)比以前更快更猛烈；存在更多的煙和明顯更大量的有毒氣體。所有這些來自于在每日生活中使用聚合物的性質(zhì)。migrate：遷移

out：放出P140-2Combustionofpolymersoccursintwobroadstages.Firstlythereisinitiationinwhichanearbysourceofheatcausesthetemperaturetorisetosuchapointthatchemicalbondsbegintobreak.Thisgenerateslowmolarmassproductsthatmigratethroughthepolymerandoutintothegasphase,theretheyundergooxidation,i.e.theyburn.

聚合物燃燒發(fā)生在兩個廣泛的領(lǐng)域。首先存在點燃階段，在熱源附近引起溫度升高達到化學(xué)鍵開始斷裂的那一點。這產(chǎn)生低摩爾質(zhì)量的產(chǎn)物它遷移經(jīng)過聚合物并放出氣體相，它們經(jīng)歷氧化過程，如它們?nèi)紵饋?。hinders：阻礙

thecombustionzone:燃燒區(qū)域

bestarvedof:缺乏P140-3Thermosetsandthermoplasticsbehavedifferentlyfromeachotherinfires.Thermosetsdonotmeltwhenheatedbutmaywellundergofurthercrosslinking.Thepresenceofsuchadditionalcrosslinkshindersmovementofanyvolatiledegradationproductsthroughthepolymermatrix.Hencethecombustionzonetendstobestarvedoffuelandforthisreasonthermosetstendtoberelativelynon-flammable.熱固性塑料和熱塑性塑料在燃燒中相互間表現(xiàn)有所不同。熱固性塑料加熱時不融化但可以進一步交聯(lián)。這種額外交聯(lián)的存在會阻礙從聚合物基體中揮發(fā)性降解產(chǎn)物的移動。因此燃燒區(qū)域趨向于缺少燃料并且由于這個原因熱固性塑料傾向于相對來說不易燃燒。residue：殘留物

char:焦渣

P140-5Polymersdonotburnwithcompleteefficiency,eventhosecomposedonlyofcarbon,hydrogen,andpossiblyoxygen.Insteadtheygiveoffsignificantamountsofsmokeandleavebehindasolidresidueofchar.Thequantityofbothsmokeandcharproducedmayvarywidely,dependingonboththefireconditionsandthematerialinvolved.聚合物不會燃燒十分完全有效，甚至僅由碳、氫和可能出現(xiàn)的氧組成。取而代之的是它們釋放出極其大量的煙并留下燒焦的固體殘渣。產(chǎn)生的煙和焦渣兩者的數(shù)量可寬范圍變化，依賴于燃燒的條件和涉及的材料兩個方面。prevailing：占優(yōu)勢的;主要的

aerate：使快速地暴露于空氣中;使通氣

P141-1Anumberofthermoplasticsundergodepolymerisation（解聚）onheating.Theseincludepoly(styrene),poly(methylmethacrylate),andpoly(oxymethylene)（聚甲醛）.Suchdepolymerisationwilloccurregardlessoftheprevailingoxygenconcentrationandunderwellaeratedconditionswillprovideareadysourceoffuelforsustainedcombustion.PVCbehavesdifferentlyinfires.TheBehaviourofIndividualPolymers

許多熱塑性塑料在熱作用下經(jīng)歷解聚。包括聚苯乙烯、聚甲基丙烯酸甲酯和聚甲醛。這種解聚發(fā)生時不考慮氧氣的濃度是否占優(yōu)勢并且，在良好的通風(fēng)條件下將對維持燃燒提供容易的燃料源。PVC在燃燒中表現(xiàn)有所不同。left

：留下的

conjugatedstructure：共軛結(jié)構(gòu)

orangy-red：橙紅色extensivedegradation:廣泛的降解P141-2ItreadilylosesHClfromalongthebackboneinaprocessthatisautocatalytic.Theproductleftbehindhasahighlyconjugatedstructurethatgivesrisetoadeeporangy-redorblackcolourandmakestheproductverybrittle.Thehydrogenchloridegivenoffisnot,ofcourse,flammablesothatdespiteextensivedegradationPVCneverundergoesself-sustainingcombustion.聚氯乙烯在燃燒過程中沿主鏈容易失去HCl這是自動催化的。留下的產(chǎn)物有高度共軛結(jié)構(gòu)它顯出橙紅色或黑色并使產(chǎn)品很脆。當(dāng)然，釋放的氯化氫不可燃燒所以盡管深度降解的PVC從來不會自行維持燃燒過程。theleastthermallystable：穩(wěn)定性最小

themajortonnagepolymers：主要的通用聚合物P141-3

Dehydrochlorination（脫去氯化氫）ofPVCwilloccuratthekindoftemperaturesusedinthecommercialprocessing,makingittheleastthermallystableofallthemajortonnagepolymers.BecauseofthisPVCalwayscontainsastabiliser,theprecisenatureofwhichwilldependontheproposedend-useoftheparticularbatchofPVC.PVC可以在商業(yè)使用過程中的溫度下發(fā)生脫去氯化氫的過程，使它在所有通用聚合物中成為熱穩(wěn)定性最差的。由于PVC總是含有穩(wěn)定劑，它的詳細性質(zhì)依賴于PVC最終使用目的。photolytically：光敏感的still:盡管如此Thestabilisersusedtoprotectagainstfiredamagearedifferentfromthoseusedtoprotectagainstdegradationinprocessing.Stillothersareusedwhenprotectionagainstphotolyticallyinduceddehydrochlorinationisneeded.用來防止燃燒損害的穩(wěn)定劑不同于那些防止降解的穩(wěn)定劑。盡管如此，其它試劑也有所使用，包括所需除氯化氫的防止光催化的試劑。taint:污染，沾污P141-3Therangeofstabilisersmayalsobeinfluencedbyotherconsiderations;forexample,PVCfilmforuseinfoodpackaginghastobestabilisedwithanadditivethatwillnotmigrateintothefoodortaintatthepointofcontact.穩(wěn)定劑的范圍也受其它條件影響，例如，用在食品包裝中的PVC薄膜必須帶附加的穩(wěn)定性，不能遷移進食品或污染與之接觸的食品。specimen：樣本，實例Inthetechnique,whichusespolymerspecimensofastandardsize,variousoxygenconcentrationsinanoxygen-nitrogenmixtureareusedandtheminimumamountthatwilljustallowflamingcombustiontocontinueforatleast3minutesisdetermined.技術(shù)上，使用標(biāo)準(zhǔn)的聚合物樣品，在氧氮混合氣體中使用各種氧氣濃度，在允許燃燒火焰至少持續(xù)3分鐘決定氧氣的最少量。Percentage:百分?jǐn)?shù)P142-1Thisvalue,expressedasapercentage,isknownastheLimitingOxygenIndex.TypicalresultsareshowninTable8.1這個值，表示為一個百分?jǐn)?shù)，被稱為極限氧指數(shù)。典型的結(jié)果見表8.1over-estimate：高估

supplemented:增補,補充;P142-2Hot,well-oxygenatedairismorelikelytoinitiatesubstantialdamagetoorganicpolymersthanthegaseousmixtureusedintheLOItest.TheuseofanartificiallylowtemperaturereducestheapparentflammabilityofthemeasuredLOIandhencemayover-estimatethesafetyofagivenpolymerunderfireconditions.BecauseoftheselimitationsdatafromtheLOItestsneedtobesupplementedbyresultsfromothertestmethods.熱，很好氧化性的空氣比LOI測定中使用的氣體混合物對有機聚合物更有可能引發(fā)實質(zhì)損害。人為使用低溫度減少LOI測量中的表面燃燒，因此可以在燃燒條件下高估給定聚合物的安全性。因為LOI測量的這些極限數(shù)據(jù)需要由其它測試方法進行補充。sought:seek的過去式

mutuallyincompatible：相互矛盾evolution

：(氣體的)放出P142-3Themajorimprovementsoughtinpolymersintermsoftheirfirebehaviourisreductionofflammability.Forcertainapplications,however,reductioninsmokeevolutionissoughtbutthesetwoaimstendtobemutuallyincompatible.Reductioninflammabilityisbroughtaboutbymakingthecombustionprocesslessefficient.IMPROVEMENTOFSTABILITYOFPOLYMERSINFIRES

根據(jù)聚合物的燃燒行為在聚合物中尋找最重要的事就是減少火焰?？墒菍τ谝欢ǖ膽?yīng)用，尋求減少煙氣釋放，但這兩個目標(biāo)傾向于相互矛盾。由燃燒過程效率下降就會帶來火焰的減少。incorporation：合并，加入

confer…on：給予assistwith：有助于

retardancy：阻止P143-1Reductioninflammabilityisachievedbytheincorporationofflameretardantsintothepolymer.Twopossibleapproachestothisareavailable;eithertheuseofadditivesblendedintothepolymeratprocessingstage(additivetype)ortheuseofalternativemonomerswhichconferreducedflammabilityonthefinalproduct(reactivetype).火焰的減少可由在聚合物中加入火焰阻礙劑完成。有兩種可能的手段來達到，可以是在加工階段使用添加劑混合進入聚合物（添加型）或使用替代性單體，它能在最終的產(chǎn)物中給予火焰減少的性能（反應(yīng)型）。Anumberofelementshavebeenfoundtoassistwithconferringflameretardancyonpolymers,themainonesbeingbromine,chlorine,nitrogen,andphosphorus.P143-2Alargenumberofmaterials,generallyinorganicinnature,havebeenusedasadditive-typeflameretardants,ofwhichhydratedalumina(水合氧化鋁)andantimony（銻）oxideareamongthemostimportant.大量的物質(zhì)，一般自然界的無機物，可以被用作添加型火焰阻礙劑，其中水合氧化鋁和氧化銻是最重要的。metalborates：金屬硼酸鹽

imperviousglassylayer：不可滲透的玻璃狀層

hydrogenhalide:HClhalogengas:鹵素氣體P143-3Theuseofcertainglassysolids,suchasmetalborates,mayleadtotheformationofanimperviousglassylayerwhichpreventsthepassageofvolatilesouttothecombustionzone.Finallytheincorporationofchlorinatedorbrominatedadditivesmaygiverisetosubstantialquantitiesofeitherhydrogenhalideorhalogengaswithinthevolatiles,thusquenching（淬火）vapourphaseoxidationinthecombustionzone.一定玻璃狀固體的使用，如金屬硼酸鹽，可以導(dǎo)致不可滲透的玻璃狀層的形成，它防止揮發(fā)物傳遞出燃燒區(qū)域。最終氯化物和溴化物添加劑的加入可以在揮發(fā)物中提供相當(dāng)數(shù)量的氯化氫或鹵素氣體，因此在燃燒區(qū)域淬滅氣相的氧化反應(yīng)。refersto：涉及

this：指代前面比較的結(jié)果P143-4Increatinglessflammablegradesofpolymeruseisoftenmadeoftheso-calledantimony-halogensynergism（銻-鹵素協(xié)同作用）.Synergismreferstothesituationinwhichthejointeffectisgreaterthanthesumoftheindividualeffectsandinthecaseofantimony-halogensynergism//thismeansthatsmalleramountsofeachmaterialcanbyusedthanwouldhavebeenexpectedonthebasisoftheindividualeffectsofaddingSb2O3orincorporatingco-monomerscontainingbromineorchlorine.為達到較小的燃燒級別聚合物使用的是所謂的銻-鹵素協(xié)同作用。協(xié)同作用涉及下列情況，其中加合作用大于個別作用的效果并且在銻-鹵素協(xié)同作用中，這意味著比單獨加入Sb2O3和加入溴化物或氯化物共單體所起的作用，每種物質(zhì)的用量更小。evolve：放出P143-5Themechanismofantimony-halogensynergismisbelievedtobe:Polymer,incombustionconditions,beginstoevolve

HClorHBr;HClorHBrreactswithSb2O3togiveSbOX;銻-鹵素協(xié)同作用據(jù)信如下：聚合物，在燃燒條件下，開始放出HCl或HBrHCl或HBr與Sb2O3反應(yīng)生成SbOX；III.SbOXundergoesself-reactiontoyieldSbX3,agas,plusSb2O3;IX.SbX3quenchestheflamebyactingasaradicaltrapandbypreventingaccesstooxygen.Assuch,itismoreeffectivethaneitherofthehydrogenhalides

orthehalogengasesasanagentforquenchingcombustion.III.SbOX經(jīng)歷自反應(yīng)產(chǎn)生SbX3，一種氣體，加上Sb2O3IX.SbX3由反應(yīng)作為自由基捕捉劑并且防止氧化過程從而淬滅火焰。由此，比氯化氫或鹵素氣體作為試劑滅除燃燒這會更有效。flameextinctiontime：火焰熄滅時間

minimum：最小值P144-1Thereisgoodexperimentalevidenceforthismechanismofantimony-halogensynergism,mostsignificantlythatflameextinctiontimeisaminimumforpolymerscontainingantimonyandhalogeninthemoleratio1:3.銻-鹵素協(xié)同作用的這個作用機理有很好的實驗證據(jù)，最有意文的是對于含有銻和鹵素摩爾比1：3的聚合物火焰熄滅時間是一個最小值。Weathering:耐候性

ultravioletlight:紫外光P144-2Weatheringisabroadetermthatisappliedtothechangesthattakeplaceinapolymeronexposureoutofdoors.Themainagentsofweatheringaresunlight(particularlyultravioletradiation),temperature,thermalcycling,moistureinvariousforms,andwind.WEATHERINGOFPOLYMERS

耐候性是個寬泛的術(shù)語，它被用于暴露在戶外的聚合物所發(fā)生的變化。耐候性的主要介質(zhì)是陽光（尤其是紫外線），溫度、熱循環(huán)，各種形式的濕氣和風(fēng)。Themaindegradationisbroughtaboutbyultravioletlight,assistedbycontributionsfromthevisibleandnear-infraredportionsoftheelectromagneticspectrum.Inparticularthenear-infraredradiationacceleratesdegradationreactionsbyraisingthetemperature.主要的降解由紫外光帶來，輔助于電磁光譜中可見光和近紅外輻射部分。特別是，近紅外輻射通過升高溫度來加速降解反應(yīng)。and

：后省略了to

bothseasonallyandgeographically:即隨季節(jié)性也隨地理性P144-3Allofthefactorsinvolvedinweathering,includingboththeamountand(書上錯寫成of)intensityofsunlight,varybothseasonallyandgeographically.Tounderstandfullyandpredicttheweatheringbehaviourofanypolymerrequiresinformationaboutexactlyhowthesefactorsvaryandhowtheythencontributetotheoveralldegradationprocess.耐候性涉及的所有的因素，包括陽光的強度和量，即隨季節(jié)性也隨地理性發(fā)生變化。為了完整和預(yù)見性的理解任一聚合物的耐候性行為必需精確知道關(guān)于這些因素怎樣變化和它們對整個降解過程的貢獻的信息。experienced:經(jīng)受的P144-4Solarradiationexperiencedbypolymersattheearth’ssurfacehastwocomponents,directradiationfromthesunandindirectradiationfromthesky.AtallpartsoftheEarth’ssurface,solarirradianceishighestatnoon,whenthesunishighestinthesky.Theactualintensity,though,variesgeographically.在地球表面聚合物經(jīng)受太陽輻射有兩種成份，來自于太陽的直接輻射和從天空中間接的輻射。地球所有的表面，中午的太陽輻射最高，此時太陽在天空中最高。雖然實際的強度隨地域不同而變。Thisisduenotonlytoregionalvariationsintheamountofdirectsunlight,butalsobecausetheclarityoftheatmospherevariesgeographically,dependingontheamountofwatervapourorpollutinggasesthatarepresentlocally.這不僅是由于直射陽光的量發(fā)生地域性變化，而且是因為空氣的清澈度也隨地理性變化，信賴于水蒸氣的量或局部出現(xiàn)的污染氣體。P144-5OnepartoftheworldwheresolarirradianceisverystrongisinFlorida.Hightemperatures,directsunlight,andrelativeabsenceofpollutionallcontributetothisstrongirradianceandbecauseofittherearemanysitesinFloridathatareusedtotesttheresistanceofpolymerstooutdoorexposure.世界上太陽輻射很強的一個區(qū)域是Florida。高溫、直射的陽光和相對少的污染導(dǎo)致強的輻射，并且因此在Florida存在很多地點用于對聚合物暴露在戶外的抵抗性進行測試。banksofrack:架子的邊坡

Inclined:傾向于

subjectively:客觀的Typicallybanksofracksholdingpolymerorpaintsamplesinclinedat45C°areexposedtothesunforseveralmonthsorevenyears.Theextentofphotodegradationmaythenbeassessed,oftenfairlysubjectively,basedontheunderstandingthatpolymersampleswhichsurviveinthehighirradianceofFloricawilltendtodowellalmostanywhereelseintheworld.典型的固定聚合物或油漆試樣的架子的坡板傾斜成45C°，暴露在陽光下幾個月或甚至幾年。能達到的光降解程度常常是客觀變化的，基于這樣一種理解，聚合物樣品能在Florica的高輻射陽光下存留下來也就能在世界上任何其它地方很好的存留下來。peroxyradicals：過氧自由基P145-1Sunlightaloneisnotresponsibleforthedegradationofpolymers;theprocessisassistedbythepresenceofoxygensothatphoto-oxidationisabletooccur.Oxygencanpromotepolymerdegradationinthepresenceofsolarradiationinanumberofways.Freeradicalsformedinthepolymerbyphotolysiscanreactwithoxygentoformperoxyradicalswhichinitiateaseriesofradicalchainreactions.只有陽光不會造成聚合物降解；過程中氧氣的存在會幫助光氧化能夠發(fā)生。在陽光輻射下氧氣能以許多方式促進聚合物的降解。在聚合物中由光化學(xué)形成的自由基能與氧反應(yīng)形成過氧自由基，它引發(fā)一系列的自由基鏈?zhǔn)椒磻?yīng)。excitedstate：激發(fā)態(tài)

deterioration：惡化,變壞;退化P145-1Theseprocessesoccurbyreactionwithoxygeninthegroundstate.However,reactionofground-stateoxygenwithsensitisers,suchasdyesintheexcitedstate,causestheformationofexcited-stateoxygen.Intermsofelectronicspinstates,thisgeneratesthemorereactivesingletoxygenfromthelessreactivetripletoxygen（三重氧）.Singletoxygenisresponsibleforthedeteriorationinsunlightofunsaturatedpolymericmaterialssuchasnaturalrubberandsyntheticelastomers.這些過程靠與氧的反應(yīng)在基態(tài)發(fā)生?？墒?，基態(tài)氧與光敏劑的反應(yīng)，如在激發(fā)態(tài)下的染料，引起激發(fā)態(tài)氧的形成。根據(jù)電子自旋狀態(tài)，這使從反應(yīng)性低的三重氧產(chǎn)生了更多的反應(yīng)性單線態(tài)氧。單線態(tài)氧會促使不飽和聚合物材料如天然橡膠和合成彈性體在陽光下降解。alone:單獨

rutile:金紅石P145-2Polymersarerarelyusedaloneinapplicationsinvolvingout-doorexposurebutareusuallyeitherfilledorpigmented.Pigmentsorfilersmaythemselvesinfluencethecourseofphoto-oxidativedegradation.Forexampletherutileformoftitaniumdioxideisthemostwidelyusedwhitepigmentforbothpolymersandpaintsanditmayeitherassistorinhibitdegradation.涉及到暴露在戶外應(yīng)用的聚合物很少單獨使用但是常常加入填料或被染色。染料或填料自身可以影響光氧化降解。例如二氧化鈦的金紅石形式對于聚合物和油漆二者是使用最廣泛的白色染料并且它即可以助推也可以阻止降解。TiO2mayassistdegradationbecauseitactsasaphotosensitiser.Thisoccursbythefollowingmechanism:二氧化鈦可以助推降解因為它作用如同一種光敏劑。這由如下機理進行。singlet:單(譜)線,單線態(tài)

P145-3Henceeitherthereactivesingletoxygenmoleculeoroxygenatomsareproduced;eitherofthesemayinitiateradicalchainprocessesthatleadtodegradation.因此產(chǎn)生活性的單線態(tài)分子氧或氧原子，它們中的任何一個都可以引發(fā)自由基鏈?zhǔn)竭^程從而導(dǎo)致降解。Alternatively：二者選一

predominates:優(yōu)勢P146-1

Alternativelybecauseofthedegreetowhichitbothreflectswhitelightandabsorbsintheultraviolet,itmayinhibitphotodegradation.WhichofthesetwopossibititiespredominatesdependsinavarietyoffactorsincludingtheconcentrationoftheTiO2（titaniumdioxide）pigmentused,thenatureofanysurfacetreatments,andtheextenttowhichthepolymeritselfisabletoresistphotodegradation.另外因為一定程度上它即可以反射白光又可以吸收紫外線，它可以阻止光降解。這兩種可能中哪一個占優(yōu)勢信賴于所用二氧化鈦的濃度、表面處理的性質(zhì)和聚合物自身的范圍是否抵抗光降解等一系列因素。bestressed：強調(diào)

cooperative：合作的P146-2Thetestingofpolymersforresistancetoweatheringisdifficult.Apartfromexposingsamplesinplacesthatnaturallyexperiencehighsolarirradiance,suchasFlorida,variousartificialweatheringdevicesareavailable.Itmustbestressedthattheseareartificialweatheringdevices.Theycannotaccelerateweathering,becausethefactorswhichcauseweatheringarecomplexandcooperative.Hencetheycannotbereadilyaccelerated.聚合物耐候性的測試是不同的。除了暴露在天然具有高太陽輻射的地方，如Florida，還可以使用人造的耐候性裝置。必須強調(diào)的就是人造耐候性裝置的存在。它們不能加速氣候浸蝕，因為引起氣候浸蝕的影響因素是復(fù)雜而協(xié)同的。因此它們不能輕易被加速。artificialweathering

：人造耐候性

comprise：包含P146-3Thereisgreatdifficultyincorrelatingresultsobtainedfromartificialweatheringtestswiththoseinvolvingoutdoorexposure.Partoftheproblemisthatitisnotpossibletomimicsolarradiationcompletely.Solarradiationcomprisesaspreadofwavelengths,withintensitiesvaryingaccordingtowavelength.涉及暴露在戶外從人造耐候性測試中獲得相關(guān)結(jié)果存在很大困難。部分問題是不可能完全模擬出太陽輻射。太陽輻射包含一股光波，強度根據(jù)波長發(fā)生變化。Artificialweatheringusingarelampscannotcompletelyreproduceboththespectralspreadandthevariationinintensity,eventhoughthebasicrequirementsofheat,ultravioletlight,andmoisturemaybemet.人工耐候性用的燈光不能完全再現(xiàn)光譜寬度和強度變化，雖然具備基本必需的熱、紫外光和濕度。incident：易發(fā)生的;伴隨而來的

Interpretation：解釋;闡明careandexperience：用心和經(jīng)驗

substitute：替代品P146-4AnotherdifficultywithtestingisthatexposureofspecimensatasitesuchasFloridamaygiveadifferentpatternofdegradationfromtestsinvolvingexposureatasitehavinglessincidentsunlight.Interpretationoftheresultsofanyweatheringtest,whetherartificialornatural,requirescareandexperience.Intheendthereisnosubstituteforseeinghowthepolymerperformswhenexposedtotheconditionsunderwhichitwilleventuallybeused.測試中另一個困難是把樣品暴露在一個象Florida這樣的地方，與一個涉及較少陽光的地方，可能給出不同的降解情況。任何耐候性測試結(jié)果的解釋，無論是人造的還是天然的，都要求用心和經(jīng)驗豐富。最后，當(dāng)聚合物暴露在最終使用的條件下，要觀察它的表現(xiàn)到底怎樣，不存在替代品。additives：添加劑P146-5Avarietyofadditivesareavailableforincorporationintopolymerstoactasantioxidants.AselectionoftheseadditivesislistedinTable8.2togetherwiththenamesofthepolymersforwhichtheyaremostsuited.PROTECTIONOFPOLYMERSFROMPHOTO-OXIDATION很多添加劑可以加入聚合物中用作抗氧化劑。表8.2列出了可選擇的添加劑和與它們最適合的聚合物名稱。exhaustive：徹底的;詳盡無疑的，消耗的

interferingwith:干擾P146-6WhilstnotanexhaustivelistthecompoundsgiveninTable8.2dorepresentthemajorclassesofantioxidant.OnefeaturethatisclearfromthisTableisthattheseantioxidantstendtobeeffectiveinmanydifferentpolymers,showingthattheyoperate

by

interferingwiththeagentsofphoto-oxidationrather

thanbyaspecificinteractionwiththeparticularpolymer.與此同時在表8.2中列出的化合物并不詳盡確實代表了抗氧劑的主要種類。從這個表中一個表顯的特點是這些抗氧劑在很多不同聚合物中都是有效的，這表明它們起作用靠得是干擾光氧化過程的介質(zhì)，而不是靠與特定聚合物的具體相互反應(yīng)。Indoingso：靠這種作法

competewith：與…競爭

appropriate：適當(dāng)?shù)?恰當(dāng)?shù)?相稱的hydrogen-donating:可提供H的P147-1Onegeneralmechanismbywhichantioxidantsactisbyreactionwithperoxyradicals.Indoingsotheycompetewiththepolymer,thusreducingtheextenttowhichthedegradationmediatedbyperoxyradicals.Inthepresenceofappropriatehydrogen-donatingantioxidantsperoxyradicalsundergooneoftwopropagationsteps(Reaction8.1or8.2).抗氧化作用的一般機理是與過氧化自由基反應(yīng)?？窟@種作法它們與聚合物競爭，因此減少由過氧化自由基引起降解的范圍。在適當(dāng)?shù)目商峁〩的抗氧劑的存在下過氧化自由基經(jīng)歷兩個增長步驟中的一個。substitutedphenols:取代的苯

secondaryaromaticamines.:第二芳族的胺P147-2TherateconstantofReaction8.1issuchgreaterthantherateconstantofReaction8.2,whichmeansthatantioxidantsofthistypecanbeusedinverylowconcentrationswithgoodeffect.Atypicalthermoplasticwouldcontainonly0.01%-0.5%bymassofsuchanantioxidant.Typicalcompoundswhichworkbythismechanismincludesubstitutedphenolsandsecondaryaromaticamines.反應(yīng)8.1是速率常數(shù)比反應(yīng)8.2式的要大，這意味著這種類型的抗氧劑只要很低的濃度就能達到很好的效果。一個典型的熱塑性塑料僅含有0.01%-0.5%質(zhì)量含量這樣抗氧劑。以這種作用機理的典型化合物包括取代的苯和第二芳族的胺。radicaltrapping:自由基捕捉劑P147-3Analternativemechanismbywhichadditivesmayprotectpolymersfromphoto-oxidationisradicaltrapping.Additiveswhichoperatebythismechanismarestrictlylightstabilisersratterthanantioxidants.Themostcommonmaterialsinthisclassarethehinderedamines(受阻胺),whicharetheusualadditivesfortheprotectionofpoly(ethylene)andpoly(propylene)..添加劑可以保護聚合物不發(fā)生光氧化的另一個機理是自由基捕捉。以這種機理作用的添加劑是嚴(yán)格意義上的光穩(wěn)定劑而不是抗氧化劑。這種最普通的物質(zhì)是受阻胺，它常作為保護聚乙烯和聚丙烯的添加劑。TheactionofthesestabilisersisoutlinedinReactions8.3-8.5這種穩(wěn)定劑的作用在反應(yīng)式8.3-8.5中列出。consume:消耗P148-1Theseadditivesarethusabletotrapbothalkyl（烷基）andperoxyradicals.Inthiswaytheyinterferewiththepropagatingstepsofthedegradationprocess.Sinceoverallthenitroxyl（硝酰）

radicalsarenotconsumedinthismechanismtheseadditivesareeffectiveatlowconcentrationsinthepolymer.因此這種添加劑能夠捕捉烷基和過氧化自由基。用這種方法它們干擾降解過程的增長步驟。因此整個砂酰自由基在這個機理中并不消耗在聚合物中添加劑在很低的濃度下就十分有效。decomposer:分解劑

fragmentating：分裂hydroperoxide：過氧化氫P148-2Thefinalpossiblemodeofactionforanantioxidantisasaperoxide

decomposer.Inthesequencesthatleadtophotodegradationofapolymerthereadyfragmentatingofthehydroperoxidegroupstofreeradicalsistheimportantstep.Ifthisstepisinterferedwithbecausetheperoxidehasundergoneanalternativedecompositionthismajorsourceofinitiationisremoved.這是主句抗氧劑最終可能的作用方式是作為一個過氧化自由基分解劑。在一系列導(dǎo)致聚合物的光降解過程中過氧化氫分裂產(chǎn)生自由基是重要的步驟。如果這一步驟因為過氧化自由基經(jīng)歷另一個分解過程被干擾，引發(fā)降解的主要來源v被去除了。expansion：擴展;擴張;膨脹

thevalencestate：價態(tài)P148-2Theadditiveswhichactbydecomposinghydroperoxidegroupsincludecompoundscontainingeitherdivalentsulfer(二價硫)ortrivalentphosphorus(三價磷).Themechanisminvolvesexpansionofthevalencestateoftheelementtoaccommodate（接納）

oxygen,asillustratedinReactions8.6and8.7.作用于分解過氧化氫基團的添加劑包括含有二價硫或三價磷的化合物。機理涉及到為了接納氧元素價態(tài)的增加，如反應(yīng)式8.6和8.7中所示。synergistic：協(xié)同的

convert…into：轉(zhuǎn)變?yōu)閜oly(alkenes),：聚烯烴P148-3Dependingonthenatureofthesulfurorphosphoruscompoundused,theproductR2S=OorR3P=OmayundergoanumberoffurtherreactionswithROOHgroups,allofwhichconvertthehydroperoxidegroupintoanalcohol.Thesecompoundstendtobeonlyweaklyeffectivesoaregenerallyusedinconjunctionwithsynergistic

promoters(促進劑).Suitablemixturesareusedtostabiliseavarietyofpolymersincludingpoly(alkenes),

ABS,andpoly(stryrene).依據(jù)所用硫化物和磷化物的性質(zhì)，產(chǎn)物R2S=O或R3P=O可以經(jīng)歷與ROOH基團的進一步反應(yīng)，所有反應(yīng)把過氧化氫基團轉(zhuǎn)變?yōu)榱u基。這些化合物反應(yīng)僅是弱效的，所以常常用于與協(xié)同促進劑一起起作用。適當(dāng)?shù)幕旌衔锉挥糜谠S多聚合物起穩(wěn)定作用，包括聚烯烴、ABS和聚苯乙烯。toxicity:毒性impart：給予depletes：用盡P149-1Compoundsforuseasantioxidantshavetofulfilanumberofrequirementsinadditiontotheireffectivenessinstabilisingthepolymer.Forexample,theymusthavelowtoxicityandbyinexpensive.Theymustalsobyfullycompatiblewiththepolymerofchoicesinceotherwisetheytendtomigratetothesurfacewheretheyimpart

anunacceptableappearance.Anysuchmigrationalsodepletestheconcentrationinthebulkwhichleadstoalossofprotectionforthepolymer.除了對聚合物穩(wěn)定性有效之外，用作抗氧劑的化合物必須滿足許多要求。例如，它們必須低毒且價格低廉。它們也必須與所選聚合物充分相容因為不相容使之傾向于向表面遷移，在表面它們一無是處（給予一個不能接受的表現(xiàn)）。任何這樣的遷移也耗盡本體中的濃度導(dǎo)致失去對聚合物的保護。resistantto：抑制

canbeconferredby：獲得P149-2Themajorcommercialpolymersarethepolyolefins,poly(ethylene)andpoly(propylene),andtheseareextremelyresistanttobiologicaldegradation.Somedegreeofbiodegradability（生物降解能力）canbeconferredbycopolymerisingtheprincipalmonomerwithamorepolarmonomer,typicallyanester.BIOLOGICALDEGRADATIONOFPOLYMERS通用聚合物有聚烯烴、聚乙烯和聚丙烯，它們具有極大的抗生物降解性。一定程度的生物降解能力能由主單體與極性單體共聚獲得，如酯類。donotfullydegrade：不完全降解since：由于

afinelydividedpowder：良好分散的粉末

debris：殘渣obtrusive：傷害P149-2Alternatively,blendingthepolyolefinwithahighlybiodegradablepolymer,suchasstarch,canbeemployed,suchmaterialsdonotfullydegrade

sincethepolyolefincontinuestoresistsuchdegradation.However,theproductofdegradationtendstobeafinelydividedpowder,ratherthanlargepiecesofpolymericdebris,andthismaybelessobtrusiveintheenvironment.另外，能使用聚烯烴與高度生物降解的聚合物如淀粉共聚，這種物質(zhì)不會完全降解因為聚烯烴能抵抗這種降解?？墒?，降解的產(chǎn)物傾向于是一種良好分散的粉未，而不是大塊的聚合物殘渣，這可以降低對環(huán)境的傷害。microorganisms：微生物

susceptible：敏感的biologicalattack:生物進攻P149-3Syntheticpolyestersarecapableofbeingdegradedbymicroorganisms,polyesterswithaliphatic（脂肪族的）backbonesbeingmoresusceptibletosuchdegradationthanthosewitharomaticbackbones.Polyamides（聚酰胺）oflowmolarmass,too,maybedegradedbymicroorganisms,butcommercialpolyamides,thenylons,tendtobeoftoogreatamolarmassandhencearealmostcompletelyresistanttobiologicalattack.合成聚酯是能被微生物聚解的，帶有脂肪族主鏈比帶芳香族主鏈的的聚酯對這種降解更為敏感。低摩爾質(zhì)量的聚酰胺也可以被微生物降解，但商用聚酰胺，尼龍，傾向于摩爾質(zhì)量太大，因此幾乎完全能夠抵抗生物的攻擊。metabolised:新陳代謝polarsubstituents：極性取代基

preferably：最好是

biodegradablepackaging：生物可降解的包裝P149-5Ontheotherhandtherearepolymersthatarecapableofbeingdegraded,generallyinacontrolledway,toyieldlowmolarmassmoleculesthatcanbesafelymetabolisedbylivingorganisms.Polymersofthistypeneedtohaverelativelypolarsubstituents,preferablyesterandhydroxylgroups（羥基）.Onesuchpolymerthathasachievedsometechnicalsuccess,forexampleasamaterialforbiodegradablepackaging,ispoly(hydroxybutyrate)(PHB聚羥基丁酸酯).另一方面存在能夠被降解的聚合物，一般以一種可控的方式，產(chǎn)生低摩爾質(zhì)量的分子，它能被活的生物安全的代謝掉。這種聚合物需要相對極性的取代基，最好是酯和羥基。一種成功達到這一技術(shù)的聚合物，例如作為生物可降解包裝的材料，是PHB聚羥基丁酸酯。bindsto：粘合

analogue：類似物

P149-6Biodegradationisanenzyme-catalysed（酶催化的）process,andtypicallyoccursintwostages.Inthefirstofthem,theenzymebindstothepolymer,afterwhich,inthesecondstage,hydrolytic（水解的）

cleavage（分裂）occurs.Generallythemore

hydrophilicthepolymer,themoresusceptibleitistohydrolysis.生物降解是一個酶催化的過程，典型的發(fā)生步驟有兩個。第一個步驟，酶粘合到聚合物上，之后，第二個步驟，發(fā)生水解分裂.一般，聚合物的親水性越大，水解的敏感性越高。amorphous：非結(jié)晶的，無定形的However,otherfactorsalsoaffectthesusceptibilitytowardshydrolysis（水解）,suchasmolarmassandcrystallinity.Lowermolarmasspolymersdegradequickerthanthe