Hydroxyethyl cellulose (HEC) yog non-ionic, dej-soluble polymer muab los ntawm cellulose los ntawm kev hloov tshuaj. Nws pom kev siv dav hauv ntau qhov kev lag luam vim nws cov khoom tshwj xeeb, xws li thickening, stabilizing, thiab kev ua yeeb yaj kiab muaj peev xwm. Hauv cov ntawv thov uas pH ruaj khov yog qhov tseem ceeb, kev nkag siab yuav ua li cas HEC coj raws li qhov sib txawv pH yog qhov tseem ceeb.
Lub pH stability ntawm HEC yog hais txog nws lub peev xwm los tswj nws cov qauv kev ncaj ncees, rheological zog, thiab kev ua tau zoo thoob plaws ntau thaj chaw pH. Qhov kev ruaj ntseg no yog qhov tseem ceeb hauv kev siv xws li cov khoom siv tu tus kheej, tshuaj, txheej, thiab cov ntaub ntawv tsim kho, qhov pH ntawm ib puag ncig ib puag ncig tuaj yeem sib txawv heev.
Qauv:
HEC feem ntau yog synthesized los ntawm reacting cellulose nrog ethylene oxide nyob rau hauv alkaline tej yam kev mob. Cov txheej txheem no ua rau muaj kev hloov pauv ntawm pawg hydroxyl ntawm cov pob txha cellulose nrog hydroxyethyl (-OCH2CH2OH) pawg. Qhov degree ntawm kev hloov pauv (DS) qhia qhov nruab nrab ntawm cov pawg hydroxyethyl ib chav tsev anhydroglucose hauv cov saw cellulose.
Khoom:
Solubility: HEC yog soluble nyob rau hauv dej thiab ua kom meej, viscous daws.
Viscosity: Nws nthuav tawm pseudoplastic lossis shear-thinning tus cwj pwm, txhais tau tias nws cov viscosity txo qis hauv kev ntxhov siab. Cov cuab yeej no ua rau nws muaj txiaj ntsig zoo hauv cov ntawv thov uas ntws yog qhov tseem ceeb, xws li cov xim pleev xim thiab txheej txheej.
Thickening: HEC imparts viscosity rau cov kev daws teeb meem, ua rau nws muaj txiaj ntsig zoo li tus neeg sawv cev thickening nyob rau hauv ntau yam formulations.
Zaj duab xis-forming: Nws tuaj yeem tsim cov yeeb yaj kiab hloov tau yooj yim thiab pob tshab thaum ziab, uas yog qhov zoo hauv cov ntawv thov xws li cov nplaum thiab cov coatings.
pH Stability ntawm HEC
Qhov pH ruaj khov ntawm HEC yog cuam tshuam los ntawm ntau yam, suav nrog cov qauv tshuaj ntawm cov polymer, kev cuam tshuam nrog ib puag ncig ib puag ncig, thiab cov khoom ntxiv uas muaj nyob hauv cov qauv.
pH stability ntawm HEC nyob rau hauv txawv pH ntau yam:
1. Acid pH:
Ntawm acidic pH, HEC feem ntau ruaj khov tab sis tuaj yeem raug hydrolysis nyob rau lub sijhawm ntev nyob rau hauv cov mob hnyav acidic. Txawm li cas los xij, hauv kev siv feem ntau, xws li cov khoom tu tus kheej thiab cov txheej txheem, qhov twg acidic pH ntsib, HEC tseem nyob ruaj khov nyob rau hauv cov pH ntau yam (pH 3 txog 6). Tshaj li pH 3, qhov kev pheej hmoo ntawm hydrolysis nce, ua rau maj mam txo qis hauv viscosity thiab kev ua haujlwm. Nws yog ib qho tseem ceeb los saib xyuas cov pH ntawm cov qauv uas muaj HEC thiab kho lawv raws li qhov tsim nyog kom muaj kev ruaj ntseg.
2. Tsis muaj pH:
HEC qhia kev ruaj ntseg zoo nyob rau hauv nruab nrab pH tej yam kev mob (pH 6 txog 8). Qhov pH no muaj ntau yam hauv ntau daim ntawv thov, suav nrog tshuaj pleev ib ce, tshuaj, thiab khoom siv hauv tsev. HEC-muaj formulations khaws lawv viscosity, thickening zog, thiab tag nrho cov kev ua tau zoo nyob rau hauv no pH ntau. Txawm li cas los xij, yam xws li qhov kub thiab txias thiab lub zog ionic tuaj yeem cuam tshuam kev ruaj ntseg thiab yuav tsum tau xav txog thaum lub sij hawm tsim kho.
3. Alkaline pH:
HEC tsis ruaj khov nyob rau hauv alkaline tej yam kev mob piv rau acidic los yog nruab nrab pH. Nyob rau qib pH siab (siab dua pH 8), HEC tuaj yeem raug degradation, ua rau txo qis viscosity thiab poob ntawm kev ua haujlwm. Alkaline hydrolysis ntawm ether kev sib txuas ntawm cov pob txha cellulose thiab cov pab pawg hydroxyethyl tuaj yeem tshwm sim, ua rau muaj kev sib tsoo thiab txo qhov hnyav molecular. Yog li ntawd, nyob rau hauv alkaline formulations xws li detergents los yog cov ntaub ntawv tsim kho, lwm yam polymers los yog stabilizers yuav nyiam dua HEC.
Cov yam ntxwv cuam tshuam rau pH Stability
Ntau yam tuaj yeem cuam tshuam rau pH stability ntawm HEC:
Degree ntawm Kev Hloov Kho (DS): HEC nrog cov txiaj ntsig DS siab dua yuav muaj kev ruaj khov nyob thoob plaws pH ntau dua vim muaj kev hloov pauv ntawm hydroxyl pawg nrog hydroxyethyl pawg, uas txhim kho cov dej solubility thiab tiv thaiv hydrolysis.
Kub: Qhov kub siab tuaj yeem ua rau muaj tshuaj lom neeg, suav nrog hydrolysis. Yog li ntawd, kev tswj kom tsim nyog cia thiab ua haujlwm kub yog qhov tseem ceeb rau kev khaws cia pH ruaj khov ntawm HEC-muaj cov qauv.
Ionic Strength: Siab concentrations ntawm ntsev los yog lwm yam ions nyob rau hauv lub formulation tuaj yeem cuam tshuam qhov ruaj khov ntawm HEC los ntawm kev cuam tshuam nws cov solubility thiab kev cuam tshuam nrog dej molecules. Lub zog ionic yuav tsum tau ua kom zoo kom txo qis cov teebmeem destabilizing.
Additives: Kev koom ua ke ntawm cov additives xws li surfactants, preservatives, los yog buffering agents tuaj yeem cuam tshuam cov pH stability ntawm HEC formulations. Kev ntsuam xyuas kev sib raug zoo yuav tsum tau ua kom ntseeg tau tias muaj kev sib tw ntxiv thiab kev ruaj ntseg.
Daim ntawv thov thiab Formulation Considerations
Nkag siab txog pH stability ntawm HEC yog qhov tseem ceeb rau cov neeg tsim khoom hauv ntau qhov kev lag luam.
Nov yog qee qhov kev txiav txim siab tshwj xeeb ntawm daim ntawv thov:
Cov Khoom Siv Kho Tus Kheej: Hauv cov tshuaj zawv plaub hau, cov tshuaj kho mob, thiab tshuaj pleev ib ce, tswj cov pH hauv qhov xav tau ntau yam (feem ntau nyob ib puag ncig nruab nrab) ua kom muaj kev ruaj ntseg thiab kev ua tau zoo ntawm HEC raws li tus neeg sawv cev thickening thiab suspending.
Pharmaceuticals: HEC yog siv rau hauv qhov ncauj tshem tawm, tshuaj kho qhov muag, thiab cov tshuaj pleev ib ce. Cov qauv tsim yuav tsum tau tsim thiab khaws cia hauv cov xwm txheej uas khaws cia HEC ruaj khov kom ntseeg tau tias cov khoom siv tau zoo thiab lub neej txee.
Coatings thiab Paints: HEC yog ua hauj lwm raws li ib tug rheology modifier thiab thickener nyob rau hauv dej-raws li xim thiab coatings. Formulators yuav tsum sib npaug pH qhov yuav tsum tau ua nrog rau lwm yam kev ua tau zoo xws li viscosity, leveling, thiab tsim zaj duab xis.
Cov Khoom Siv Siv: Hauv kev tsim cov cementitious, HEC ua raws li tus neeg saib xyuas dej thiab txhim kho kev ua haujlwm. Txawm li cas los xij, alkaline tej yam kev mob hauv cov cement tuaj yeem cuam tshuam HEC kev ruaj ntseg, yuav tsum tau ua tib zoo xaiv thiab kev hloov kho.
Hydroxyethyl cellulose (HEC) muaj txiaj ntsig rheological thiab ua haujlwm zoo hauv ntau daim ntawv thov. Kev nkag siab txog nws cov pH stability yog qhov tseem ceeb rau cov qauv tsim kom ruaj khov thiab muaj txiaj ntsig zoo. Thaum HEC qhia kev ruaj ntseg zoo nyob rau hauv nruab nrab pH tej yam kev mob, kev txiav txim siab yuav tsum tau ua rau acidic thiab alkaline ib puag ncig los tiv thaiv degradation thiab ua kom pom kev ua haujlwm zoo. Los ntawm kev xaiv cov qib HEC uas tsim nyog, txhim kho cov txheej txheem kev ua kom zoo, thiab ua raws li cov txheej txheem cia tsim nyog, cov qauv tsim tuaj yeem siv cov txiaj ntsig ntawm HEC thoob plaws ntau thaj chaw pH.
Lub sij hawm xa tuaj: Mar-29-2024