1. Cov nyhuv ntawm qhov kub thiab txias
Nws tau paub los ntawm kev txheeb xyuas dhau los hais tias viscosity ntawm plastics yog qhov ua haujlwm ntawm shear tus nqi, tab sis cov viscosity ntawm plastics kuj tseem cuam tshuam los ntawm qhov kub thiab txias. Yog li ntawd, nws yog qhov tseem ceeb ntawm qhov tseem ceeb los kawm txog cawv ntawm kub ntawm viscosity tsuas yog thaum lub shear tus nqi tas li. Feem ntau hais lus, qhov viscosity rhiab ntawm cov yas yaj yog qhov muaj zog dua li ntawm qhov kev txiav txim siab. Cov txiaj ntsig tau qhia tias qhov viscosity ntawm yaj yaj txo qis exponentially nrog qhov nce ntawm qhov kub.
Qhov no vim tias qhov kub nce ntxiv, nws yuav ua kom nrawm nrawm nrawm ntawmlwg me thiab molecular cov saw, uas yuav txo qhov tsis nkag ntawm cov xov tooj yas molecular saw thiab qhov kev ncua deb ntawm molecules, yog li ua rau txo qis viscosity. Nws yog yooj yim rau daim ntawv, tab sis cov khoom muaj qhov loj shrinkage tus nqi, uas yuav ua rau lub cev tsis muaj zog. Qhov ntsuas kub tsawg dhau, cov yaj viscosity yog qhov loj, qhov khiav yog qhov nyuaj, qhov tsis txaus ntseeg, thiab lub elasticity loj, uas tseem yuav ua rau cov duab tsis ruaj khov ntawm cov khoom tsis zoo.
Tab sis qhov viscosity ntawm plastics sib txawv nws txawv nrog qhov kub. Qhov tshwj xeeb tshaj yog ntawm polyformaldehyde rau qhov kub yog polyethylene, polypropylene thiab polystyrene, thiab qhov tsis hnov mob tshaj plaws yog cellulose acetate
Hauv kev xyaum, rau cov yaj nrog qhov kub thiab txias rhiab heev, nws muaj peev xwm txhim kho cov kev ua kom zoo ntawm plastics los ntawm kev txhim kho molding kub thaum lub sij hawm molding txheej txheem, xws li PMMA, PC, CA, PA. Tab sis rau cov plastics uas tsis hnov zoo, nws tsis pom tseeb los txhim kho cov kev ua kom txaus los ntawm kev nce hauv qhov kub thiab txias, yog li nws tsis yog feem ntau siv txhawm rau txhim kho cov yam ntxwv ntws.
Piv txwv li, POM, PE, PP thiab lwm cov kab uas tsis ncov qaum, txawm tias qhov kub nce siab heev, qhov viscosity tsawg heev. Ntxiv mus, qhov kub thiab txias yuav tsum tau txwv los ntawm qee yam kev mob, uas yog, ntsuas kub ntawm cov pwm yuav tsum tsis pub dhau ntawm cov khoom lag luam tuaj yeem tso cai ntawm cov yas, txwv tsis pub, yas yuav thim tawm. Txoj kev poob ntawm kev ua cov khoom siv yog qhov loj, qhov ua haujlwm ntawm kev mob cuam tshuam, thiab qhov poob tsis tau them nyiaj. Nws yog ntawm ntau qhov tseem ceeb los qhia qhov kev sib raug ntawm viscosity thiab kub ntawm cov ntaub ntawv los ntawm kev siv qhov loj me ntawm kev ua kom lub zog.
2. Qhov ua tau ntawm siab
Muaj qhov chaw me me ntawm cov molecules thiab cov saw hauv cov yas yaj, uas yog, thiaj li hu dawb ntim. Yog li cov yas tuaj yeem ua kom zoo. Thaum txhaj, qhov siab tshaj plaws sab nrauv siab rau cov yas tuaj yeem ncav cuag kaum lossis ntau pua MPa. Nyob rau hauv lub siab, qhov kev ncua deb ntawm macromolecules poob qis, qhov ntau ntawm cov ntu ntu kev ua si poob qis, qhov kev ncua deb ntawm molecules poob qis, thiab qhov quab yuam nruab nrab ntawm cov molecules nce, uas ua rau kev cuam tshuam ntawm cov txuas ntxiv nyuaj, uas qhia tau hais tias tag nrho viscosity nce.
Tab sis qhov viscosity ntawm plastics sib txawv yog qhov sib txawv hauv tib lub siab. Polystyrene (PS) yog qhov rhiab tshaj plaws ntawm qhov siab, uas yog, thaum lub siab nce, viscosity nce sai. Piv nrog LDPE, lub siab muaj feem me me rau viscosity, thiab polypropylene yog sib npaug ntawm cov npluag nruab nrab polyethylene.
Qhov tseeb ntawm kev nce viscosity los ntawm kev nce siab pom tias nws tsis tsim nyog los nce qhov ntws ntawm cov yas yaj los ntawm kev nce siab ib leeg. Kev kub siab tuaj yeem tsis tsuas yog txhim kho txhaws ntawm cov kua dej kom meej meej, tab sis kuj tseem txhaws qhov kev ua haujlwm yuav txo qis vim qhov nce ntawm viscosity. Nws tsis tsuas yog ua rau kev siv hluav taws xob ntau dhau thiab cov khoom siv dhau los hnav, tab sis kuj ua rau qhov tsis xws luag xws li txeej thiab kev ntxhov siab sab hauv ntawm cov khoom.
Tsis tas li ntawd, qhov ua haujlwm siab dhau, thiab yuav muaj kev txhaj tshuaj tsis xws li cov khoom deformation, uas ua rau lub zog siv ntau dhau. Tab sis lub siab tsis dhau, uas yuav ua rau cov khoom tsis txaus.
Cawv ntawm qhov kub ntawm viscosity tuaj yeem pom tias cov nyhuv ntawm nce siab ntawm viscosity ntawm cov yas yaj yog zoo li ntawm kev txo qhov kub ntawm cov viscosity yas tsis pub dhau ntawm cov txheej txheem coj ua. Piv txwv li, rau ntau lub plastics, thaum lub siab nce siab txog 100 MPa, qhov hloov viscosity yog sib npaug los txo qhov kub ntawm 30-50 ℃.
3. Qhov cuam tshuam ntawm tus txiav shear
Nrog qhov nce ntawm shear tus nqi, qhov viscosity ntawm plastics feem ntau poob qis. Tab sis nyob rau hauv rooj plaub ntawm tus nqi shear qis thiab tus nqi shear siab, cov viscosity yuav luag tsis hloov nrog tus nqi shear. Hauv qab qhov ua ntej ntawm qee qhov kub thiab siab, qhov viscosity ntawm plastics sib txawv.
Los yog, txawm hais tias qhov viscosity ntawm cov yas feem ntau melts poob nrog qhov nce ntawm shear tus nqi, qhov rhiab ntawm cov plastics sib txawv rau shear tus nqi (shear kev ntxhov siab) yog qhov sib txawv.
Kev Pom Ntsej muag ntawm lub ntsiab lus no yog tias viscosity ntawm plastics yuav raug txo qis thiab cov kev ua haujlwm ntws yuav tau zoo los ntawm kev nce tus nqi shear nyob rau hauv qee cov shear tus nqi ntau. Txawm li cas los xij, nws yog qhov zoo dua los xaiv cov txheej txheem kev hloov kho nyob rau hauv cov khoom ntawm cov roj viscosity uas tsis rhiab rau shear tus nqi, txwv tsis pub, qhov hloov ntawm cov plaub txig yuav ua rau kev ua haujlwm tsis ruaj khov thiab qhov tsis xws ntawm cov khoom yas.
4. Cov cawv ntawm cov qauv yas
Rau cov plastics, qhov viscosity ntawm plastics nce nrog qhov nce ntawm txheeb ze nruab nrab molecular phaus ntawm qhov ntsuas kub. Qhov loj dua ntawm cov txheeb ze phaus nyhav, lub zog muaj zog intermolecular ntau dua, thiab ntau dua cov viscosity.
Qhov tsawg dua cov phaus nyhav ntawm cov yas, qhov tsawg dua qhov viscosity nyob ntawm shear tus nqi; qhov loj dua cov phaus nyhav, qhov ntau dua qhov viscosity dependant ntawm tus nqi shear. Cov yaj yaj viscosity thiab cov txheej txheem tsim ntawm cov khoom siv sib xyaw nrog cov dav molecular phaus faib thiab ob chav molecular phaus faib cob yog tsawg. Vim tias cov saw phaus nyhav qis me me yuav pab tau txhawm rau txhim kho qhov kev npliag ntawm cov roj yaj.
5. Qhov cuam tshuam ntawm tsis tshua muaj molecular phaus ntxiv
Tsis tshua muaj molecular tuaj yeem txo qhov kev quab yuam ntawm macromolecules, thiab ua si lub luag haujlwm ntawm" lubrication", yog li txo qhov viscosity ntawm yaj thiab txo qhov viscosity fluidization kub. Yog tias cov hnab yas thiab cov kuab tshuaj ntxiv rau, cov dej ua kom yooj yim tuaj yeem thiab ua pwm.
Hauv ntej, qhov viscosity ntawm polymer yaj ncaj qha cuam tshuam qhov nyuaj ntawm kev txhaj tshuaj molding. Yog tias qhov kub ntawm cov yas tsim yog tswj nyob hauv qab ntawm qhov kub thiab txias, cov yaj viscosity yog 50-500 pa-s thaum tus nplai shear yog 103 s-1, thiab kev txhaj tshuaj molding yog yooj yim dua. Txawm li cas los xij, yog tias viscosity loj dhau, nws yuav tsum muaj qhov siab txhaj tshuaj, qhov loj ntawm cov khoom lag luam yog tsawg, thiab cov khoom lag luam yog qhov cuam tshuam; yog tias qhov viscosity tsawg dhau, qhov tshwm sim dhau ntawm qhov hnyav yog qhov khoom loj, cov khoom lag luam tsis yooj yim yuav lav tau, hauv qhov no, lub nozzle yuav tsum muaj cov khoom ntsuas tus kheej.
