Qhov Tseem Ceeb Qhov Sib Txawv - Iav Hloov Kub Kub vs Melting Kub
Kev tshawb xyuas cov khoom thermal ntawm elastomers yog qhov tseem ceeb los txiav txim siab lawv daim ntawv thov zaum kawg thiab cov txheej txheem tsim khoom. Cov khoom siv thermal ntawm elastomers tuaj yeem raug tshuaj xyuas siv cov kev ntsuas sib txawv xws li kev hloov pauv kub, qhov muaj txiaj ntsig kub, muaj peev xwm kub, thermal conductivity, kub dependence ntawm txhua yam khoom thiab coefficient ntawm linear thermal expansion. Muaj ob hom kev ntsuas kub uas tuaj nyob rau hauv kev hloov pauv kub xws li, iav hloov pauv kub (T g) thiab kub kub (Tm). Hauv kev lag luam polymer, cov ntsuas kub no yog siv rau kev txheeb xyuas cov ntaub ntawv thiab lawv qhov tsis zoo. Kev hloov pauv kub ntawm cov polymers tuaj yeem ntsuas tau zoo heev los ntawm kev siv cov cuab yeej siab tshaj plaws xws li dynamic mechanical analyzer (DMA) thiab sib txawv scanning calorimeter (DSC). Thaum lub iav hloov pauv kub, qhov hloov pauv hloov tau nyob rau theem los ntawm khov mus rau iav los yog vice versa tshwm sim nyob rau hauv cov cheeb tsam amorphous ntawm lub polymer vim qhov kev hloov ntawm qhov kub thiab txias, qhov kub ntawm melting kub, lub crystalline los yog semi-crystalline cheeb tsam ntawm ib tug polymer hloov mus rau ib tug. khoom amorphous theem. Qhov no yog qhov sib txawv tseem ceeb ntawm cov iav hloov pauv kub thiab melting kub.
iav hloov pauv kub yog dab tsi?
Lub iav hloov pauv kub yog qhov kub ntawm qhov khov lossis roj hmab lub xeev ntawm amorphous lossis semi-crystalline polymer hloov mus rau nkig, iav lub xeev. Qhov no yog ib qho kev hloov pauv rov qab. Hauv qab iav hloov pauv kub, cov polymers yog tawv thiab nruj zoo li iav. Tshaj qhov kub hloov pauv iav, cov polymers pom cov khoom khov lossis cov khoom siv roj hmab nrog tsawg dua rigidity. Kev hloov iav yog qhov kev txiav txim thib ob vim tias muaj kev hloov pauv hauv cov derivatives. Cov kev hloov pauv hauv polymer saum toj no thiab hauv qab no tshwm sim vim yog lub zog molecular vim yog lub zog hloov pauv. Qhov kub no cuam tshuam zoo heev los ntawm cov qauv ntawm cov molecules. Ntxiv mus, nws kuj nyob ntawm qhov zaus ntawm cyclic deformation, cov nyhuv ntawm cov khoom xyaw xws li plasticizers, fillers, thiab lwm yam., thiab tus nqi ntawm kev hloov ntawm qhov kub thiab txias..
Daim duab 01: Qhov ntom ntom ntawm qhov kub thiab txias
Raws li kev soj ntsuam kev soj ntsuam, nws pom tau tias nyob rau hauv ib tug symmetrical polymer, iav hloov kub yog ib nrab ntawm nws melting kub, thaum nyob rau hauv ib tug unsymmetrical polymer, iav hloov kub yog 2/3 ntawm nws melting nqi (nyob rau hauv degrees. Kelvin). Txawm li cas los xij, cov kev sib raug zoo no tsis yog universal thiab muaj kev sib txawv ntawm ntau cov polymers. Kev hloov iav yog qhov tseem ceeb los txiav txim siab txog kev ua haujlwm ntawm cov khoom siv polymer, ntsuas kev hloov pauv thiab qhov xwm txheej ntawm cov lus teb rau kev ntxhov siab.
Qhov Kub Kub Kub yog dab tsi?
Melting yog lwm qhov tseem ceeb ntawm kev hloov pauv thermal hauv polymers. Feem ntau, melting kub yog qhov kub ntawm qhov kev hloov pauv tshwm sim; Piv txwv li, khoom ua kua los yog kua rau vapor.
Daim duab 02: Melting
Txawm li cas los xij, raws li cov polymers raws li kev txhawj xeeb, lub melting kub yog qhov kub ntawm qhov kev hloov ntawm crystalline los yog semi-crystalline theem mus rau ib qho khoom amorphous theem. Melting yog thawj qhov kev txiav txim endothermic cov tshuaj tiv thaiv. Lub enthalpy ntawm melting ntawm lub polymer yuav siv tau los xam cov degree ntawm crystallinity, muab hais tias lub melting enthalpy ntawm 100% ntawm tib lub polymer yog paub. Paub qhov kub thiab txias yog qhov tseem ceeb heev vim nws muab lub tswv yim txog kev ua haujlwm ntawm cov khoom siv polymer.
Dab tsi yog qhov txawv ntawm iav hloov kub thiab melting kub?
Khov Hloov Kub Kub vs Melting Temperature |
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| iav hloov pauv kub yog qhov kub ntawm qhov khov lossis roj hmab lub xeev ntawm amorphous lossis semi-crystalline polymer hloov mus rau nkig, iav lub xeev. | iav hloov pauv kub yog qhov kub ntawm qhov khov lossis roj hmab lub xeev ntawm amorphous lossis semi-crystalline polymer hloov mus rau nkig, iav lub xeev. |
| Kev hloov iav yog qhov kev txiav txim thib ob. | Melting is a first order reaction. |
| gm | |
| Amorphous cheeb tsam ua roj hmab, tsis tshua muaj zog thiab tsis nkig | Crystalline cheeb tsam hloov mus rau hauv cov khoom amorphous. |
| g los yog Tm | |
| Amorphous cheeb tsam ua iav, tawv thiab nkig. | thaj chaw ruaj khov crystalline |
| Kev sib raug zoo (raws li kev soj ntsuam kev soj ntsuam) | |
| Tg=1/2 Tm (rau symmetrical polymers) | Tg=2/3 Tm (rau unsymmetrical polymers) |
Summary – Iav Transition Temperature vs Melting Temperature
Ob qho tib si iav hloov pauv thiab melting kub yog qhov tseem ceeb heev thermal hloov khoom ntawm polymers. Tshaj qhov kub hloov pauv ntawm iav, cov polymers muaj cov khoom siv roj hmab, whereas, hauv qab no kub, lawv muaj iav zog. Kev hloov iav tshwm sim hauv amorphous polymers. Melting yog qhov hloov ntawm theem ntawm crystalline mus rau cov khoom amorphous. Melting kub yog ib qho tseem ceeb los xam cov degree ntawm crystallinity. Ob qhov ntsuas kub yog qhov tseem ceeb heev los txiav txim siab qhov zoo thiab kev ua haujlwm ntawm cov polymers.
Download PDF Version of Glass Transition Temperature vs Melting Temperature
Koj tuaj yeem rub tawm PDF version ntawm kab lus no thiab siv nws rau offline hom phiaj raws li daim ntawv ceeb toom. Thov download PDF version ntawm no Qhov txawv nruab nrab ntawm iav Transition Temperature thiab Melting Temperature
