Hydroxypropylmethylcellulose (HPMC) yog ib qho kev sib xyaw uas tau dhau los ua cov khoom siv raw hauv ntau qhov kev lag luam vim nws cov khoom siv ntau yam. Nws feem ntau yog siv los ua khoom noj khoom haus additives, thickener nyob rau hauv cov tshuaj pleev ib ce, thiab txawm ib tug kho mob muaj nyob rau hauv ntau yam tshuaj. Cov cuab yeej tshwj xeeb ntawm HPMC yog nws tus cwj pwm thixotropic, uas tso cai rau nws hloov viscosity thiab ntws cov khoom raws li qee yam mob. Tsis tas li ntawd, ob qho tib si high-viscosity thiab low-viscosity HPMC muaj cov cuab yeej no, nthuav tawm thixotropy txawm tias qis dua qhov kub ntawm gel.
Thixotropy tshwm sim hauv HPMC thaum muaj kev daws teeb meem los ua shear-thinning thaum lub siab siv los yog nplawm, ua rau txo qis hauv viscosity. Tus cwj pwm no kuj tuaj yeem thim rov qab; Thaum cov kev ntxhov siab raug tshem tawm thiab cov kev daws teeb meem raug tso tseg, cov viscosity maj mam rov qab mus rau nws lub xeev siab dua. Cov cuab yeej tshwj xeeb no ua rau HPMC muaj txiaj ntsig zoo hauv ntau qhov kev lag luam vim nws tso cai rau kev ua haujlwm zoo dua thiab ua haujlwm yooj yim dua.
Raws li ib tug nonionic hydrocolloid, HPMC swells nyob rau hauv dej los tsim ib tug gel. Qhov degree ntawm o thiab gelling nyob ntawm qhov hnyav molecular thiab concentration ntawm polymer, pH thiab kub ntawm cov tshuaj. High viscosity HPMC feem ntau muaj qhov hnyav molecular thiab tsim cov viscosity gel, thaum tsis muaj viscosity HPMC muaj qhov hnyav molecular thiab tsim cov viscosity tsawg. Txawm li cas los xij, txawm hais tias qhov sib txawv ntawm qhov kev ua tau zoo, ob hom HPMCs nthuav tawm thixotropy vim kev hloov pauv uas tshwm sim ntawm qib molecular.
Kev coj tus cwj pwm thixotropic ntawm HPMC yog tshwm sim los ntawm kev sib haum xeeb ntawm cov saw hlau polymer vim kev nyuaj siab shear. Thaum shear stress yog siv rau HPMC, cov saw hlau polymer ua raws li cov kev taw qhia ntawm cov kev nyuaj siab, uas ua rau kev puas tsuaj ntawm peb-dimensional network qauv uas muaj nyob rau hauv tsis muaj kev nyuaj siab. Kev cuam tshuam ntawm lub network ua rau txo qis hauv cov tshuaj viscosity. Thaum cov kev ntxhov siab raug tshem tawm, cov saw hlau polymer rov ua raws li lawv qhov kev taw qhia qub, rov tsim lub network thiab rov ua kom muaj viscosity.
HPMC kuj nthuav tawm thixotropy hauv qab qhov kub thiab txias. Lub gel kub yog qhov kub ntawm qhov polymer chains cross-link los tsim ib lub network peb-dimensional, tsim ib gel. Nws nyob ntawm qhov concentration, qhov hnyav molecular thiab pH ntawm cov tshuaj polymer. Lub resulting gel muaj ib tug siab viscosity thiab tsis hloov sai nyob rau hauv lub siab. Txawm li cas los xij, hauv qab qhov kub thiab txias, cov tshuaj HPMC tseem ua kua, tab sis tseem muaj cov cwj pwm thixotropic vim muaj cov qauv tsim hauv ib feem. Lub network tsim los ntawm cov khoom no tawg nyob rau hauv siab, ua rau txo qis hauv viscosity. Qhov kev coj cwj pwm no muaj txiaj ntsig zoo hauv ntau daim ntawv thov uas cov kev daws teeb meem yuav tsum tau ntws yooj yim thaum nplawm.
HPMC yog ntau yam tshuaj uas muaj ntau yam tshwj xeeb, ib qho ntawm nws tus cwj pwm thixotropic. Ob qho tib si high-viscosity thiab low-viscosity HPMCs muaj cov cuab yeej no, nthuav tawm thixotropy txawm tias qis dua qhov kub ntawm gel. Cov yam ntxwv no ua rau HPMC yog ib qho tseem ceeb hauv ntau qhov kev lag luam uas xav tau cov kev daws teeb meem uas yooj yim txaus los xyuas kom meej daim ntawv thov. Txawm hais tias muaj qhov sib txawv ntawm cov khoom ntawm high-viscosity thiab low-viscosity HPMCs, lawv tus cwj pwm thixotropic tshwm sim vim kev sib raug zoo thiab cuam tshuam ntawm ib feem ntawm cov qauv tsim network. Vim nws cov khoom tshwj xeeb, cov kws tshawb fawb tau tshawb nrhiav ntau yam kev siv ntawm HPMC, vam tias yuav tsim cov khoom tshiab thiab muab cov kev daws teeb meem zoo dua rau cov neeg siv khoom thoob ntiaj teb.
Post lub sij hawm: Aug-23-2023