Hydroxypropyl methylcellulose (HPMC)yog ib qho polymer compound uas yaj tau hauv dej uas siv dav hauv kev tsim kho, tshuaj, khoom noj thiab tshuaj lom neeg. Nws yog ib qho cellulose ether uas tsis yog ionic tau los ntawm kev hloov kho tshuaj ntawm cov cellulose ntuj, nrog cov khoom zoo thickening, emulsification, stabilization thiab zaj duab xis-tsim. Txawm li cas los xij, nyob rau hauv qhov kub siab, HPMC yuav dhau los ua thermal degradation, uas muaj qhov cuam tshuam tseem ceeb rau nws qhov kev ruaj khov thiab kev ua tau zoo hauv kev siv.
Cov txheej txheem thermal degradation ntawm HPMC
Qhov kev puas tsuaj ntawm HPMC feem ntau suav nrog kev hloov pauv lub cev thiab kev hloov pauv tshuaj lom neeg. Kev hloov pauv lub cev feem ntau yog pom tseeb tias yog dej evaporation, kev hloov pauv iav thiab kev txo qis viscosity, thaum kev hloov pauv tshuaj lom neeg cuam tshuam nrog kev puas tsuaj ntawm cov qauv molecular, kev ua haujlwm pab pawg sib cais thiab cov txheej txheem carbonization kawg.
1. Theem kub qis (100–200°C): dej ua pa thiab pib lwj
Nyob rau hauv qhov kub qis (kwv yees li 100 ° C), HPMC feem ntau dhau los ntawm dej evaporation thiab iav hloov pauv. Vim tias HPMC muaj qee qhov dej khi, cov dej no yuav maj mam evaporate thaum lub sijhawm cua sov, yog li cuam tshuam rau nws cov khoom rheological. Tsis tas li ntawd, qhov viscosity ntawm HPMC kuj tseem yuav txo qis nrog qhov nce ntawm qhov kub. Cov kev hloov pauv hauv theem no feem ntau yog kev hloov pauv hauv cov khoom lub cev, thaum cov qauv tshuaj tseem tsis hloov pauv.
Thaum qhov kub tseem nce mus txog 150-200 ° C, HPMC pib ua cov tshuaj lom neeg ua ntej. Nws feem ntau pom tseeb hauv kev tshem tawm cov pab pawg ua haujlwm hydroxypropyl thiab methoxy, ua rau qhov hnyav molecular txo qis thiab kev hloov pauv ntawm cov qauv. Nyob rau theem no, HPMC tuaj yeem tsim cov khoom me me uas tsis muaj zog, xws li methanol thiab propionaldehyde.
2. Theem kub nruab nrab (200-300 ° C): kev puas tsuaj ntawm cov saw hlau tseem ceeb thiab kev tsim cov molecule me me
Thaum qhov kub nce ntxiv mus txog 200-300 ° C, qhov kev lwj ntawm HPMC tau nrawm dua. Cov txheej txheem lwj tseem ceeb suav nrog:
Kev tawg ntawm Ether bond: Cov saw hlau tseem ceeb ntawm HPMC txuas nrog los ntawm cov khoom siv glucose ring, thiab cov ether bonds hauv nws maj mam tawg hauv qab qhov kub siab, ua rau cov saw hlau polymer lwj.
Kev ua kom qhuav: Cov qauv suab thaj ntawm HPMC yuav dhau los ua kev ua kom qhuav ntawm qhov kub siab los tsim cov khoom nruab nrab tsis ruaj khov, uas tau tawg ua cov khoom tsis ruaj khov.
Kev tso tawm cov khoom me me uas tsis muaj zog: Thaum lub sijhawm no, HPMC tso tawm CO, CO₂, H₂O thiab cov khoom me me uas muaj cov organic, xws li formaldehyde, acetaldehyde thiab acrolein.
Cov kev hloov pauv no yuav ua rau qhov hnyav molecular ntawm HPMC poob qis heev, qhov viscosity poob qis heev, thiab cov khoom siv yuav pib tig daj thiab txawm tias tsim cov coking.
3. Theem kub siab (300–500°C): carbonization thiab coking
Thaum qhov kub nce siab tshaj 300 ° C, HPMC nkag mus rau theem kev puas tsuaj loj heev. Lub sijhawm no, qhov kev tawg ntxiv ntawm cov saw hlau tseem ceeb thiab kev ua kom cov tshuaj me me ua rau muaj kev puas tsuaj tag nrho ntawm cov qauv khoom, thiab thaum kawg tsim cov pa roj carbonaceous (coke). Cov tshuaj tiv thaiv hauv qab no feem ntau tshwm sim hauv theem no:
Kev puas tsuaj ntawm oxidative: Thaum kub siab, HPMC dhau los ua qhov tshuaj tiv thaiv oxidation los tsim CO₂ thiab CO, thiab tib lub sijhawm tsim cov pa roj carbonaceous residues.
Cov tshuaj tiv thaiv coking: Ib feem ntawm cov qauv polymer raug hloov mus ua cov khoom sib xyaw tsis tiav, xws li cov pa roj carbon dub lossis cov coke seem.
Cov khoom uas yaj tau: Txuas ntxiv tso cov hydrocarbons xws li ethylene, propylene, thiab methane.
Thaum cua sov hauv huab cua, HPMC tuaj yeem hlawv ntxiv, thaum cua sov thaum tsis muaj oxygen feem ntau tsim cov khoom seem carbonized.
Cov yam tseem ceeb uas cuam tshuam rau kev puas tsuaj ntawm HPMC los ntawm thermal
Qhov kev puas tsuaj ntawm HPMC los ntawm thermal yog cuam tshuam los ntawm ntau yam, suav nrog:
Cov qauv tshuaj lom neeg: Qib ntawm kev hloov pauv ntawm hydroxypropyl thiab methoxy pawg hauv HPMC cuam tshuam rau nws qhov kev ruaj khov thermal. Feem ntau hais lus, HPMC nrog cov ntsiab lus hydroxypropyl siab dua muaj kev ruaj khov thermal zoo dua.
Huab cua ib puag ncig: Hauv huab cua, HPMC feem ntau yuav raug oxidative degradation, thaum nyob rau hauv ib puag ncig inert roj (xws li nitrogen), nws qhov thermal degradation qeeb dua.
Tus nqi cua sov: Kev cua sov sai yuav ua rau kev lwj sai dua, thaum kev cua sov qeeb yuav pab HPMC maj mam carbonize thiab txo qhov tsim cov khoom siv roj volatile.
Cov dej noo: HPMC muaj qee qhov dej khi. Thaum lub sijhawm ua kom sov, qhov ua kom cov dej noo noo evaporation yuav cuam tshuam rau nws qhov kub hloov pauv iav thiab cov txheej txheem lwj.
Kev siv tau zoo ntawm kev puas tsuaj ntawm thermal ntawm HPMC
Cov yam ntxwv ntawm kev puas tsuaj thermal ntawm HPMC yog qhov tseem ceeb heev hauv nws daim ntawv thov. Piv txwv li:
Kev lag luam tsim kho: HPMC siv rau hauv cov cement mortar thiab gypsum cov khoom, thiab nws qhov kev ruaj khov thaum lub sijhawm tsim kho kub siab yuav tsum tau txiav txim siab kom tsis txhob muaj kev puas tsuaj uas cuam tshuam rau kev ua haujlwm ntawm kev sib txuas.
Kev lag luam tshuaj: HPMC yog tus neeg sawv cev tso tawm tshuaj, thiab yuav tsum zam kev lwj thaum lub sijhawm tsim khoom kub siab kom ntseeg tau tias cov tshuaj ruaj khov.
Kev lag luam zaub mov: HPMC yog cov khoom noj khoom haus ntxiv, thiab nws cov yam ntxwv thermal degradation txiav txim siab nws siv tau rau hauv kev ci thiab ua cov khoom noj kub siab.
Cov txheej txheem thermal degradation ntawmHPMCtuaj yeem muab faib ua dej evaporation thiab preliminary degradation nyob rau theem qis-kub, lub ntsiab saw cleavage thiab me me molecule volatilization nyob rau theem nruab nrab-kub, thiab carbonization thiab coking nyob rau theem siab-kub. Nws thermal stability yog cuam tshuam los ntawm cov yam xws li cov qauv tshuaj lom neeg, huab cua ib puag ncig, cua sov tus nqi thiab cov dej noo. Kev nkag siab txog lub thermal degradation mechanism ntawm HPMC yog qhov tseem ceeb heev rau kev ua kom zoo dua nws daim ntawv thov thiab txhim kho cov khoom ruaj khov.
Lub sijhawm tshaj tawm: Lub Peb Hlis-28-2025