Hydroxypropylmethylcellulose (HPMC) yog ib qho tshuaj uas tau dhau los ua cov khoom siv raw hauv ntau lub lag luam vim nws cov khoom siv ntau yam. Nws feem ntau siv ua cov khoom noj khoom haus ntxiv, ua kom tuab hauv cov tshuaj pleev ib ce, thiab txawm tias yog cov khoom siv kho mob hauv ntau yam tshuaj. Ib qho tshwj xeeb ntawm HPMC yog nws tus cwj pwm thixotropic, uas tso cai rau nws hloov pauv viscosity thiab cov khoom ntws hauv qee qhov xwm txheej. Tsis tas li ntawd, ob qho tib si high-viscosity thiab low-viscosity HPMC muaj cov yam ntxwv no, qhia txog thixotropy txawm tias qis dua qhov kub ntawm gel.
Thixotropy tshwm sim hauv HPMC thaum cov tshuaj ua shear-thinning thaum nias lossis do, ua rau viscosity txo qis. Tus cwj pwm no kuj tuaj yeem thim rov qab; thaum kev ntxhov siab raug tshem tawm thiab cov tshuaj tau tso tseg, viscosity maj mam rov qab mus rau nws lub xeev siab dua. Cov khoom tshwj xeeb no ua rau HPMC yog ib qho khoom muaj nqis hauv ntau lub lag luam vim nws tso cai rau kev siv du thiab ua tiav yooj yim dua.
Ua ib qho hydrocolloid tsis yog ionic, HPMC swells hauv dej los ua ib qho gel. Qhov degree ntawm o thiab gelling nyob ntawm qhov hnyav molecular thiab concentration ntawm cov polymer, pH thiab kub ntawm cov tshuaj. High viscosity HPMC feem ntau muaj qhov hnyav molecular siab thiab tsim cov gel viscosity siab, thaum low viscosity HPMC muaj qhov hnyav molecular qis thiab tsim cov gel viscosity tsawg dua. Txawm li cas los xij, txawm tias muaj qhov sib txawv ntawm kev ua tau zoo, ob hom HPMCs qhia txog thixotropy vim yog kev hloov pauv ntawm cov qauv uas tshwm sim ntawm qib molecular.
Tus cwj pwm thixotropic ntawm HPMC yog qhov tshwm sim ntawm kev sib phim ntawm cov saw hlau polymer vim yog kev ntxhov siab shear. Thaum kev ntxhov siab shear raug siv rau HPMC, cov saw hlau polymer sib phim rau hauv qhov kev taw qhia ntawm kev ntxhov siab siv, ua rau muaj kev puas tsuaj ntawm cov qauv network peb-seem uas muaj nyob rau hauv tsis muaj kev ntxhov siab. Kev cuam tshuam ntawm lub network ua rau txo qis viscosity ntawm cov kua. Thaum kev ntxhov siab raug tshem tawm, cov saw hlau polymer rov qab teeb tsa raws li lawv qhov kev taw qhia thawj zaug, rov tsim kho lub network thiab rov qab kho viscosity.
HPMC kuj tseem ua rau pom thixotropy qis dua qhov kub gelling. Qhov kub gel yog qhov kub uas cov saw polymer sib txuas ua ke los tsim ib lub network peb-seem, tsim ib lub gel. Nws nyob ntawm qhov concentration, qhov hnyav molecular thiab pH ntawm cov tshuaj ntawm polymer. Cov gel uas tshwm sim muaj viscosity siab thiab tsis hloov pauv sai sai hauv qab siab. Txawm li cas los xij, hauv qab qhov kub gelation, cov tshuaj HPMC tseem ua kua, tab sis tseem ua rau pom tus cwj pwm thixotropic vim muaj cov qauv network tsim ib nrab. Lub network tsim los ntawm cov khoom no tawg hauv qab siab, ua rau viscosity txo qis. Tus cwj pwm no muaj txiaj ntsig zoo rau ntau daim ntawv thov uas cov tshuaj xav tau ntws yooj yim thaum do.
HPMC yog ib yam tshuaj uas siv tau ntau yam nrog ntau yam khoom tshwj xeeb, ib qho yog nws tus cwj pwm thixotropic. Ob qho tib si siab-viscosity thiab qis-viscosity HPMCs muaj cov khoom no, qhia txog thixotropy txawm tias qis dua qhov kub gel. Cov yam ntxwv no ua rau HPMC yog ib qho khoom muaj nqis hauv ntau yam lag luam uas xav tau cov kev daws teeb meem uas tswj tau yooj yim kom ntseeg tau tias daim ntawv thov du. Txawm hais tias muaj qhov sib txawv ntawm cov khoom ntawm siab-viscosity thiab qis-viscosity HPMCs, lawv tus cwj pwm thixotropic tshwm sim vim yog kev sib phim thiab kev cuam tshuam ntawm cov qauv network tsim ib nrab. Vim nws cov khoom tshwj xeeb, cov kws tshawb fawb ib txwm 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.
Lub sijhawm tshaj tawm: Lub Yim Hli-23-2023