Hydroxypropyl methylcellulose (HPMC)yog cov dej-soluble polymer compound dav siv hauv kev tsim kho, tshuaj, zaub mov thiab tshuaj lom neeg kev lag luam. Nws yog ib qho uas tsis yog-ionic cellulose ether tau los ntawm kev hloov kho tshuaj ntawm natural cellulose, nrog zoo thickening, emulsification, stabilization thiab film-forming zog. Txawm li cas los xij, nyob rau hauv qhov kub thiab txias, HPMC yuav raug thermal degradation, uas muaj kev cuam tshuam tseem ceeb rau nws txoj kev ruaj ntseg thiab kev ua haujlwm hauv kev siv tswv yim.
Thermal degradation txheej txheem ntawm HPMC
Lub thermal degradation ntawm HPMC feem ntau suav nrog kev hloov pauv ntawm lub cev thiab tshuaj hloov pauv. Cov kev hloov ntawm lub cev feem ntau yog tshwm sim raws li dej evaporation, iav hloov pauv thiab viscosity txo, thaum cov tshuaj hloov pauv cuam tshuam nrog kev puas tsuaj ntawm cov qauv molecular, kev ua haujlwm pab pawg cleavage thiab cov txheej txheem carbonization kawg.
1. Tsawg kub theem (100-200 ° C): dej evaporation thiab pib decomposition
Nyob rau hauv qhov kub thiab txias (nyob ib ncig ntawm 100 ° C), HPMC feem ntau ua rau dej evaporation thiab iav hloov. Txij li thaum HPMC muaj qee cov dej khi, cov dej no yuav maj mam evaporate thaum cua sov, yog li cuam tshuam rau nws cov khoom rheological. Tsis tas li ntawd, qhov viscosity ntawm HPMC kuj yuav txo qis nrog qhov nce ntawm qhov kub thiab txias. Cov kev hloov hauv cov theem no feem ntau yog kev hloov pauv hauv lub cev, thaum cov qauv tshuaj tseem tsis tau hloov pauv.
Thaum qhov kub thiab txias tseem nce mus txog 150-200 ° C, HPMC pib ua cov tshuaj tiv thaiv kev puas tsuaj ua ntej. Nws yog tsuas yog tshwm sim nyob rau hauv kev tshem tawm ntawm hydroxypropyl thiab methoxy functional pawg, uas ua rau ib tug txo nyob rau hauv molecular hnyav thiab cov qauv kev hloov. Nyob rau theem no, HPMC tuaj yeem tsim cov khoom me me ntawm cov molecules me me, xws li methanol thiab propionaldehyde.
2. Nruab nrab kub theem (200-300 ° C): lub ntsiab saw degradation thiab me me molecule tiam
Thaum qhov kub thiab txias ntxiv mus rau 200-300 ° C, qhov decomposition tus nqi ntawm HPMC yog nrawm heev. Lub ntsiab degradation mechanisms muaj xws li:
Ether daim ntawv cog lus tawg: Cov saw tseem ceeb ntawm HPMC txuas nrog cov piam thaj hauv cov nplhaib, thiab cov ether bonds hauv nws maj mam tawg nyob rau hauv qhov kub siab, ua rau cov saw hlau polymer decompose.
Cov tshuaj tiv thaiv lub cev qhuav dej: Cov qauv suab thaj ntawm HPMC tuaj yeem ua rau lub cev qhuav dej ntawm qhov kub thiab txias los ua qhov nruab nrab tsis ruaj khov, uas yog ntxiv decomposed rau hauv cov khoom tsis haum.
Tso cov molecule me me volatiles: Thaum lub sij hawm no, HPMC tso CO, CO₂, H₂O thiab me me molecule organic teeb meem, xws li formaldehyde, acetaldehyde thiab acrolein.
Cov kev hloov no yuav ua rau qhov hnyav molecular ntawm HPMC poob qis, qhov viscosity poob qis, thiab cov khoom yuav pib daj thiab txawm tsim coking.
3. Kub kub theem (300-500 ° C): carbonization thiab coking
Thaum qhov kub nce siab tshaj 300 ° C, HPMC nkag mus rau theem degradation hnyav. Lub sijhawm no, kev tawg ntxiv ntawm cov saw tseem ceeb thiab cov volatilization ntawm me me molecule tebchaw ua rau kev puas tsuaj tag nrho ntawm cov khoom siv, thiab thaum kawg tsim carbonaceous residues (coke). Cov tshuaj tiv thaiv hauv qab no feem ntau tshwm sim hauv theem no:
Oxidative degradation: Thaum kub siab, HPMC raug oxidation cov tshuaj tiv thaiv los tsim CO₂ thiab CO, thiab tib lub sij hawm tsim carbonaceous residues.
Cov tshuaj tiv thaiv coking: Ib feem ntawm cov qauv polymer yog hloov mus rau hauv cov khoom siv hluav taws xob tsis tiav, xws li carbon dub lossis coke residues.
Cov khoom lag luam tsis muaj zog: Txuas ntxiv tso tawm 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 ntxwv cuam tshuam rau thermal degradation ntawm HPMC
Lub thermal degradation ntawm HPMC cuam tshuam los ntawm ntau yam, suav nrog:
Cov qauv tshuaj: Qhov kev hloov pauv ntawm hydroxypropyl thiab methoxy pawg hauv HPMC cuam tshuam rau nws cov thermal stability. Feem ntau hais lus, HPMC nrog cov ntsiab lus hydroxypropyl ntau dua muaj cov thermal stability zoo dua.
Cov huab cua nyob ib puag ncig: Hauv huab cua, HPMC yog qhov ua rau oxidative degradation, thaum nyob rau hauv ib qho chaw inert gas (xws li nitrogen), nws thermal degradation tus nqi qeeb dua.
Cov cua sov: Cov cua kub ceev yuav ua rau kom tawg sai dua, thaum cua sov qeeb tuaj yeem pab HPMC maj mam carbonize thiab txo cov khoom lag luam gaseous volatile.
Cov ntsiab lus noo noo: HPMC muaj qee cov dej khi. Thaum lub sij hawm cua sov txheej txheem, evaporation ntawm noo noo yuav cuam tshuam rau nws cov iav hloov kub thiab degradation txheej txheem.
Kev siv tswv yim cuam tshuam ntawm thermal degradation ntawm HPMC
Cov yam ntxwv thermal degradation ntawm HPMC yog qhov tseem ceeb hauv nws daim ntawv thov. Piv txwv li:
Kev tsim kho kev lag luam: HPMC yog siv rau hauv cov cement mortar thiab gypsum cov khoom, thiab nws cov kev ruaj ntseg thaum lub sij hawm siv kub kub yuav tsum raug txiav txim siab kom tsis txhob degradation cuam tshuam rau kev sib koom ua ke.
Kev lag luam kws tshuaj: HPMC yog cov tshuaj tswj kev tso tawm cov tshuaj, thiab kev decomposition yuav tsum raug zam thaum lub sij hawm kub kub ntau lawm los xyuas kom meej cov tshuaj stability.
Kev lag luam khoom noj khoom haus: HPMC yog cov khoom noj khoom haus ntxiv, thiab nws cov yam ntxwv thermal degradation txiav txim siab nws qhov kev siv tau hauv kev kub kub thiab kev ua haujlwm.
Thermal degradation txheej txheem ntawmHPMCtuaj yeem muab faib ua dej evaporation thiab ua ntej degradation nyob rau hauv qis-kub theem, lub ntsiab saw cleavage thiab me me molecule volatilization nyob rau hauv nruab nrab-kub theem, thiab carbonization thiab coking nyob rau hauv high-temperature. Nws thermal stability yog cuam tshuam los ntawm tej yam xws li cov qauv tshuaj, ambient cua, cua sov npaum li cas thiab ya raws. Nkag siab txog cov txheej txheem thermal degradation ntawm HPMC yog qhov muaj txiaj ntsig zoo los txhim kho nws daim ntawv thov thiab txhim kho cov khoom ruaj khov.
Lub sij hawm xa tuaj: Mar-28-2025