Cov pa hauv qhov pa thaum lub caij ultraviolet (UV) tua tau yog ib qho teeb meem uas tau ua rau cov neeg plaguing:
Thaum muab luam tawm hauv pa, cov pa oxygen feem ntau ua rau cov txheej hauv qab kom zoo thiab cov nplaim yuav tsum tau ua kom zoo thiab tsis muaj teeb meem.
Oxygen inhibition tuaj yeem ua rau ntau cov oxidising lug xws li hydroxyl, carbonyl thiab peroxy tej pawg nyob ntawm cov txheej, uas yuav muaj feem xyuam rau kev ruaj ntseg ntev ntawm lub txheej, thiab tseem yuav cuam tshuam txog qhov nyuaj, lub zog thiab khaus ntawm tus cured zaj duab xis. kev ua tau zoo.
vim li cas?
Lub xeev hauv lub xeev ntawm cov khoom siv dav dav yog ib lub xeev hu ua, thiab lub xeev O2 ruaj khov yog ib qho hauv peb lub xeev, thiab muaj ob qho tib si electrons uas muaj tib qho kev cob qhia. Yog li, nws competes nrog lub polymerization ntawm dawb radicals kom haus dawb radicals.
Txij li feem ntau cov txheej txheem photocuring yog ua nyob rau hauv cov huab cua ib ncig, thiab cov ntawv tseem ceeb yog cov ntaub ntawv nrog cov npoo loj heev / ntim sib piv xws li coatings thiab inks, O2 muaj qhov tsis kam rau cov dawb radical polymerization ntawm cov ntaub ntawv photocurable. Sau ua ke.
Tshwj xeeb tshaj yog thaum cov thickness film thin, cov concentration ntawm cov pa oxygen nyob rau hauv oily organic system feem ntau tsawg dua los yog sib npaug rau 2 × 10-3 mol / L, uas tsis tsuas inhibits lub polymerization ntawm yaj oxygen molecules nyob hauv lub cev formulation, tab sis nyob rau hauv txoj kev txheej txheem curing thaum lub sijhawm kev yees duab. Kev noj cov oxygen molecules, cov pa oxygen nyob saum npoo ntawm cov txheej kuj tuaj yeem ceev nrawm rau hauv qhov txheej txheem kho kom zoo, txuas ntxiv kom tabkaum ntawm lub polymerization. Thawj cov txheej txheem oxygen concentration hauv lub cev yog qhov tsawg heev thiab tseem yoojyim rau haus. Rau ib qho kaw kaw, txheej txheem uas cov thawj nyob hauv radicals tsis haus cov pa oxygen yog tshuam sib npaug rau lub sij hawm pib lub caij tawm polymerization. Kuj hais lus, cov pa oxygen uas tawm sab nraud mus rau sab hauv ntawm cov txheej txheej yog qhov tseem ceeb tshaj plaws rau qhov hymering polymerization. Oxygen inhibition kuj tseem yuav tshwm sim rau hauv cov txheej txheej ntawm cov txheej los yog hauv tag nrho cov txheej thinner, vim cov pa oxygen nyob hauv cheeb tsam diffuse yooj yim dua hauv cov chaw no.
Cov pa phem txav ntawm cov hom deg - quenching, scavenging thiab oxidation. Lub meej mechanism yog raws li nram no:
Kev tsim txom
Tus triplet O2 nyob rau hauv lub xeev hauv lub xeev yuav raug reacted ua ib tug quencher nrog ib tug initactor photactive (qhia los ntawm Phi) tsim ib lub complex, ua li no quenching tus yees duab uas excites lub triplet xeev. Cov txheej txheem no yog qhia raws li hauv qab no:
Lub Sij Hawm Lub Sij Hawm (Phhi) * → (Lub Npe) *, (Phi) * + (O2) → Lub Npe (O2)
Nyob rau hauv cov txheej txheem saum toj no, O2 zoo siab rau lub koomhaum ua haujlwm hauv lub xeev, thiab lub thaij duab xa rov qab los ntawm lub xeev txoj kev zoo siab mus rau hauv av hauv lub xeev, li no hindering cov cim ntawm cov kev tawm dag zog. Feem ntau cov duab pyrolysis muaj lub neej luv luv ntawm kev lom zem triplet. Ua ntej tus thawj coj siab zoo siab nrog O2, tus thawj coj tau raug tshem tawm, yog li qhov yuav tau muaj kev sib tw ntawm O2 thiab tus yees duab los ntawm tus neeg tau nyiaj tsawg. Feem ntau yuav tsis quav ntsej txog.
Ntshiab
Lub xeev hauv lub xeev O2 yog qhov tseem ceeb ntawm ob chav radical, yog li nws muaj kev sib ntxiv muaj zog ntxiv rau cov nquag ua haujlwm thaum lub sij hawm yees duab [k> 109 / (mol · s)], ua ib lub chaw ruaj khov ua rau lub cev tsis haum. Cov txheej txheem no muaj kev ceev ntiag tug thiab muaj peev xwm sib tw nrog qhov kev sib ntxiv ntawm cov neeg ua haujlwm nyob rau lub monomer, thiab muaj qhov tseem ceeb hindrance rau txoj kev ua polymerization. Nws tuaj yeem muab faib ua cov kab lus nram no:
Cov neeg nyob hauv paus pib pib polymerization ntawm lub monomer.
R · + CH2QCXY → R-CH2-C · XY + monomer → polymer
Tiv thaiv dawb radicals ntxiv rau O2.
R · + O2 → R─OUTO · (peroxy radical)
R-CH2-C · XY + O2 → R-CH2-CXY-OO
Oxidation
Cov pa oxygen tuaj yeem tau oxidize dawb radicals uas tau raug polymerized nrog monomers rau peroxides, tiv thaiv polymerization ntawm monomers.
Obviously, nyob rau hauv tag nrho peb cov xwm txheej, tus nqi ntawm polymerization yuav txo tau thiab tsim cov tshuaj peroxide yuav cuam tshuam rau kev ua tau zoo ntawm kev kho cov txheej. Nws yuav tsum raug sau tseg tias qhov tshuaj tiv thaiv tus nqi ntawm radical R thiab O 2 yog 104 mus rau 105 npaug loj dua cov tshuaj tiv thaiv tus nqi ntawm qhov monomer molecule, yog li txawm tias tsuas yog ib qho me me ntawm cov pa oxygen nyob rau hauv lub txheej, cov tshuaj tiv thaiv ntawm R · thiab O 2 tsis tuaj yeem lees paub. Thaum cov yeeb yaj kiab radical ROO generated. Txij li thaum ROO · yog qhov chaw ruaj khov heev thiab tsis muaj peev xwm pib pib polymerization, muaj cov O2 uas siv cov kab mob dhia ua pa R,, uas ua rau qhov tshuaj tiv thaiv polymerization txo kom tsawg thiab pom lub sijhawm induction. Yog li, O2 yog ib qho polymerization inhibitor rau dawb radical polymerization ntawm ib qhov system ntawm qhov kub thiab txias.
Muaj cov pa oxygen inhibition polymerization txoj kev
Cov kev siv lub cev: txoj hauv kev tiv thaiv cov pa roj carbon monoxide, cov nplaim dej, zaj duab xis, muaj zog lub teeb irradiation, faib irradiation
Kev siv tshuaj: Ntxiv cov paug ua kom muaj roj hydrogen - thiol, amine, ether acrylate (acrylate tuaj yeem ua ke nrog lub txheej kom tiv thaiv qhov chaw tawg, tab sis kuj txo qis); muab hydrogen atom muaj peev xwm nyob rau hauv tib lub mob: thiol hoob> Amines> Ethers
Ua ib qho amine ua piv txwv, cov tshuaj tiv thaiv yog raws li nram no: muaj 6 yam dej qab ntsev ntawm amine, uas yuav haus cov pa 6 oxygen.
Tom qab ib co kev sim ntawm cov qauv no, peb tuaj mus rau cov lus xaus hauv qab no:
Txawm hais tias cov khoom siv curing lossis khoom qis tsis zoo, yog tias ntev li ntawm thiol, ammonia lossis ether hloov acrylate tuaj yeem txhim kho qhov teeb meem ntawm deg;
Qhov deg reactivity tsub kom raws li cov concentration ntawm cov hloov kho acrylate.
Sulfhydryl pawg tuaj yeem ua haujlwm nrog hluav taws xob nrog polyether acrylates lossis cov txheej txheem reactive;
Hloov cov formulation los yog tuab ntawm txheej kuj tuaj yeem muab qhov teeb meem deg. Tshem tawm qhov nrug ntawm lub zog uas qis qis rau cov nqos dej los tiv thaiv kom tsis txhob muaj kev kub ntxhov los ntawm kev rhuav tshem.