HydroxyPropyyl methylcellulose (HPMC)yog dej-soluble polymer compound dav siv hauv kev tsim kho, tshuaj, zaub mov thiab tshuaj lom neeg. Nws yog ib qho tsis-ionic cellulose cellulose tau los ntawm cov cellulose tshuaj ntawm ntuj thickuled, nrog zoo thickening, emulsification, ruaj khov thiab zaj duab xis-ua cov khoom. Txawm li cas los xij, nyob rau hauv cov kev mob siab, HPMC yuav yauv ua tsis tau thermal, uas muaj qhov cuam tshuam tseem ceeb rau nws cov kev siv.
Cov txheej txheem thermal degradation ntawm hpmc
Cov thermal degradation ntawm HPMC tsuas yog suav nrog hloov lub cev thiab hloov tshuaj. Kev hloov pauv lub cev feem ntau yog ua kom muaj dej evaporation, thaum muaj kev hloov pauv ntawm cov qauv molecular, cov pab pawg ua haujlwm tau zoo thiab cov roj carbonancation zaum kawg.
1. Tsawg Kub theem (100-200 ° C): Dej evaporation thiab pib decogosition
Raws li cov xwm txheej kub tsawg (nyob ib ncig ntawm 100 ° C), HPMC tsuas yog undergoes dej evaporation thiab kev hloov pauv lub khob. Txij li thaum HPMC muaj qee qhov nqi ntawm cov dej ua haujlwm, cov dej no yuav maj mam yaj thaum lub sijhawm cua sov, yog li cuam tshuam nws cov khoom siv rheological. Ib qho ntxiv, cov viscosity ntawm HPMC tseem yuav txo qis nrog qhov ntsuas kub. Cov kev hloov pauv hauv theem no feem ntau yog hloov pauv ntawm lub cev muaj zog, thaum lub sijhawm tshuaj lom neeg tseem tsis hloov pauv.
Thaum qhov ntsuas kub txuas ntxiv nce mus rau 150-200 ° C, HPMC pib yauv mus rau kev txwv tsis pub muaj txiaj ntsig. Nws yog feem ntau yog manifested hauv kev tshem tawm ntawm hydroxypropyl thiab methoxy cov pab pawg ua haujlwm, ua rau muaj kev txo qis hauv cov kev hloov pauv. Nyob rau theem no, HPMC yuav tsim ib qho me me ntawm cov molatile me me, xws li methanol thiab profionaldehyde.
2. Nruab Nrab Kub (200-300 ° C): Cov saw loj degradation thiab me molecule tiam
Thaum qhov kub tau nce ntxiv mus rau 200-300 ° C, qhov kev txiav txim siab ntawm HPMC yog qhov nrawm nrawm. Lub ntsiab degradation mechanism muaj xws li:
Ethaws txoj kev sib tsoo: lub saw hlau tseem ceeb ntawm HPMC txuas nrog los ntawm cov ntiv nplhaib zoo nkauj, thiab lub ether tawm hauv nws qhov kub thiab txias, ua rau lub zog polymer kom lwj.
Lub cev qhuav dej: Cov khoom noj qab zib hauv HPMC yuav dhau mus rau lub cev qhuav dej ntawm cov khoom siv kub tsis ruaj khov, uas yog decomposed txuas ntxiv mus rau hauv cov khoom lag luam volatile.
Tso tawm ntawm cov me me molatiles volatiles: nyob rau theem no, HPMC tso tawm cov khoom siv, xws li formaldehyde, acetaldehyde thiab promolein.
Cov kev hloov pauv no yuav ua rau kev hnyav molecular ntawm HPMC kom poob qis, lub viscosity poob ntau, thiab cov khoom yuav pib tig daj thiab txawm tias tsim coking.
3. Kev kub siab theem (300-500 ° C): carbonancy thiab coking
Thaum qhov kub nce siab tshaj 300 ° C, HPMC nkag mus rau theem kev ua phem rau theem. Nyob rau lub sijhawm no, tawg tawg ntxiv ntawm cov saw hlau tseem ceeb thiab volatilization ntawm cov qauv me me ua rau kev rhuav tshem ntawm cov qauv khoom, thiab thaum kawg tsim cov pa roj carbonace (Coke). Cov tshuaj tiv thaiv hauv qab no feem ntau tshwm sim hauv qib no:
Oxidative kev mob siab: Thaum kub, HPMC undergoes oxidation oxidation cov tshuaj tiv thaiv los tsim colbonacace o, thiab tib lub sijhawm tsim cov pa roj carbonaceous.
COKING RAWS: Ib feem ntawm cov qauv polymer yog hloov mus rau cov khoom sib txuas ua tiav, xws li cov carbon xim dub lossis nqaij npuas.
Cov khoom siv volatile: txuas ntxiv tawm hydrocarbons xws li ethylene, propylene, thiab metrane.
Thaum rhuab nyob rau hauv huab cua, HPMC tuaj yeem hlawv ntxiv, thaum muaj cua sov thaum tsis muaj pa oxygen feem ntau cov qauv cov roj carbonized.
Yam cuam tshuam rau kev cuam tshuam thermal ntawm HPMC
Lub thermal degradation ntawm HPMC cuam tshuam los ntawm ntau yam, suav nrog:
Cov qauv tshuaj: cov qib ntawm kev hloov pauv ntawm hydroxyprropyl thiab methoxy pawg hauv HPMC cuam tshuam rau nws cov khoom ruaj khov. Feem ntau hais lus, HPMC nrog ntau dua hydroxypropylopyl cov ntsiab lus tau zoo dua thermal stability.
Cov huab cua ambient: Nyob rau hauv huab cua, HPMC yog nquag mus rau oxidative tsis zoo li cas (xws li nitrogen), nws thermal degradation tus nqi yog qeeb.
Cov cua sov: cua sov sai yuav ua rau muaj kev cuam tshuam sai, thaum cov roj qeeb qeeb pab HPMC kom txo qis ntawm cov khoom lag luam garatous.
Cov ntsiab lus noo: HPMC muaj qee qhov ntau ntawm cov dej ua. Thaum lub sij hawm cov txheej txheem cua sov, cov evaporation ntawm cov dej noo yuav cuam tshuam nws cov pa hloov cua kub thiab cov txheej txheem kev txwv.
Cov ntaub ntawv thov cuam tshuam ntawm thermal degradation ntawm HPMC
Cov yam thermal degradation ntawm hpmc yog qhov tseem ceeb nyob hauv nws daim ntawv thov. Piv txwv li:
Kev lag luam tsim kev tsim kho: HPMC yog siv nyob rau hauv xis mas cov khoom lag luam, thiab nws cov ruaj khov thaum lub sijhawm kev ua kom muaj kev cuam tshuam rau kev ua tsis tau zoo.
Kws tsim kev lag luam: HPMC yog cov tshuaj tswj tso tawm cov neeg sawv cev tso tawm, thiab kev txiav txim siab yuav tsum zam thaum muaj kev sib zog ntawm cov tshuaj.
Cov zaub mov kev lag luam: HPMC yog cov zaub mov muaj ntxiv, thiab nws cov kev cuam tshuam thermal kev txiav txim siab txiav txim siab nws cov kev siv hauv qhov kub thiab ua haujlwm siab.
Cov txheej txheem thermal degradation ntawmHPMCYuav muab faib ua dej evaporation thiab cov kab sib npaug ntawm cov theem qis, volatized me me, thiab ua pa roj carbon monoxide thiab cocking nyob rau theem siab. Nws cov kev ruaj khov hluav taws xob cuam tshuam los ntawm cov yam xws li cov qauv tshuaj, huab cua zoo nkauj, cov ntsiab lus cua sov thiab noo noo cov ntsiab lus. To taub cov thermal degradation mechanism ntawm HPMC yog qhov muaj txiaj ntsig zoo rau kev ua kom zoo dua nws daim ntawv thov thiab txhim kho cov khoom ruaj khov.
Lub sijhawm Post: Mar-28-2025