PVA adhesives uas tau muab cog rau kev tswi tsis kev ntxias ntau

Yog li cas PVA Polyvinyl Alcohol Tshwj Xeeb Tsis Ua Tau Thaum Qhov Ntsws Siab Dua 100°C

Cov Kev Puas Tsuaj Rau Qhov Ntsws: Qhov Puas Tsuaj ntawm Cov Hydrogen Bond thiab Qhov Cim Rau Qhov Ntsiag Ntawm Cov Chain

Cov adhesive PVA tshwj xeeb yuav txhawj qhov ntsuas ntawm lawv thaum cov cim tshuaj yuav pib lossis rau 100 degrees Celsius los ntawd vim tias cov hydrogen bonds yuav pib tawg. Cov bonds no yog qhov uas nyob hauv qhov khoom thiab nyob ua ke. Thaum cov cim tshuaj pib ntau, cov molecules yuav pib khaub ncaws ntau heev li, thiab pib tawg cov kev sib xwm ntawm lawv (uas muaj ntau rau 5 rau 30 kilojoules per mole). Qhov no yog qhov pab cov polymer strands ntev pib hlub rau ib leeg tsis tau nyob ib puag ncig. Yog tsis muaj qhov kev nyob ib puag ncig no nyob hauv qhov khoom, qhov adhesive layer yuav pib muaj kev tawg thiab pib tsis tuaj yeem thaum muaj kev puas. Qhov no yuav ntau dua thaum peb pib tawg qhov 100 degree mark, vim tias PVA yuav tsis tau ib qho film solid thiab yuav pib mus rau qhov tshuaj tshuaj uas tsis tuaj yeem nyob ib puag ncig.

Cov cim tshuaj tshwj xeeb: Glass Transition (<80°C) thiab Decomposition Onset (~200°C)

Qhov performance ntawm PVA adhesive yog nyob rau ob qho thermal transitions tshwj xeeb:

• Qhov xwm txheej ntawm kev tawg (T _g ), uas poob ntawm 75–85°C, qhia tias cov khoom yuav muaj kev ua haujlwm zoo li cov khoom nyias los yog cov khoom tawg—ua rau kev tawg ntawm kev tawg rau hauv qhov chaw tawg ntau dua 60% (J. Appl. Polym. Sci. 2023).
• Pab pawg rau lub cim txoj kev tawg yuav pib thaum 200°C, tab sis kev ua haujlwm tsis zoo yuav pib ntev dua.

Qhov xwm txheej uas muaj kev nyuaj rau tshaj plaws yog ntawm T _g los yog 100°C, uas cov hydrogen bonds uas nyuaj rau tshaj plaws yog sib npaug nrog kev mob siab ntawm cov chain. Thaum 100°C, cov khoom siv tseem ceeb tsuas muaj ntau dua 20% ntawm kev tawg ntawm lub cim thib kawg—qhia tias muaj qhov xwm txheej uas nyuaj rau tshaj plaws ntawm kev tawg thiab kev ua haujlwm nyob rau hauv qhov kev siv nyob hauv kev ua haujlwm.

Cov kev tswj hwm rau kev ntxiv qhov zoo ntawm cov adhesive polyvinyl alcohol

Cov cross-linkers uas muaj boron (yog li borax): Ntxiv qhov ua kom muaj char thiab kev nyob rau hauv dej

Thaum cov lus qhia boron zoo li borax tshuas tau rau hauv PVA matrix, lawv ua cov kawg covalent cross links uas muaj qhov tseem ceeb heev rau kev pab cov khoom no kom paub yuav siv tau zoo dua thaum muaj kev cuam tshuam ntawm txias. Qhov uas dhau los yog qhov tseem ceeb dua li cas: cov kawg kim no pab ua cov khoom tshuaj uas pab tshem cov ntaub ntawv thaum muaj txias nyob rau hauv 150 thiab 200 degrees Celsius. Xyuas li qhov tshuaj tshem no yog qhov tshuaj tshem uas tuaj ntawm lub ntiaj teb uas pab tshem txias kom tsis tau rov mus rau hauv. Ntawd tib yam, khiav borax los pab tshem cov hydroxyl groups uas nyob rau hauv cov ntaub ntawv nyob rau hauv 40 thiab 60 percent, uas pab tshem cov ntaub ntawv kom tsis tau txais cov dej, tshwj xeeb tias thaum muaj dej lossis muaj dej nyob rau hauv. Txhua yam, qhov kev siv ob qhov no pab tshem cov ntaub ntawv kom muaj 20 thiab 30 feeb ntxiv ua ntej qhov ntaub ntawv poob, compared to regular old PVA, thiab tshem cov ntaub ntawv kom muaj shear strength zoo dua 2.5 megapascals tib yam li thaum muaj txias rau 100 degrees Celsius. Lub tshuab tshuab siv cov ntaub ntawv nyob rau hauv 5 thiab 10 percent yog qhov zoo tshaj plaws rau kev siv, tab sis thaum siv ntau dua no yuav pab tshem cov ntaub ntawv kom muaj kev tshem tshem heev rau kev siv.

Nano-Silica thiab Layered Double Hydroxides (LDHs): Qhia tias muaj kev nyab xeeb rau qhov cua sov thiab kev nyab xeeb rau qhov tshuaj tsis tau ua kom zoo

Thaum muab ntxiv rau hauv qhov kev sib tw 1 thiab 4% ntawm qhov loj ntawm cov khoom, nano-silica ua qhov kev sib tw zoo li qhov kev sib tw ntawm qhov kev tswj hwm uas tsis pub kev tswj hwm ntawm qhov PVA. Qhov no ua rau qhov kev tswj hwm ntawm qhov kev tswj hwm tau txo los ntawm 15 thiab 25%, thiab kuj ua rau qhov kev tswj hwm ntawm qhov kev tswj hwm tau txo los ntawm 30 thiab 50 degrees Celsius. Qhov kev tswj hwm ntawm qhov kev tswj hwm ntawm qhov kev tswj hwm kuj ua rau qhov kev tswj hwm ntawm qhov kev tswj hwm tau txo los ntawm 10 thiab 15 degrees. Cov khoom tswj hwm ntawm qhov kev tswj hwm ntawm qhov kev tswj hwm (LDHs) kuj ua qhov kev tswj hwm zoo li qhov kev tswj hwm ntawm qhov kev tswj hwm. Qhov kev tswj hwm ntawm qhov kev tswj hwm kuj ua rau qhov kev tswj hwm ntawm qhov kev tswj hwm tau txo los ntawm 35 thiab 50%. Qhov kev tswj hwm ntawm qhov kev tswj hwm ntawm qhov kev tswj hwm kuj ua rau qhov kev tswj hwm ntawm qhov kev tswj hwm tau txo los ntawm 20%.

Kev Koo Kav Lub Tswv Yim Polymer: Kev Co-polymerization thiab Kev Cross-Linking Tshiab

Kev Koo Kav Lub Tswv Yim Terpolymer (VAc-AA-MAH): Ntxiv Tg mus rau 115°C thiab Tsim Kev Tshem Tawm

Thaum peb sib npaug vinyl acetate (VAc), acrylic acid (AA), thiab maleic anhydride (MAH) los ua terpolymers, qhov tsi zoo yuav muaj kev txawj ntsuam rau lawv cov ntaub. Cov cim ntawm kev rov qab ntawm qhov cim ntawm kev rov qab yuav nyob rau hauv 115 degrees Celsius, uas yog 35 degrees siab dua li qhov peb pom rau cov ntaub PVA tshwj xeeb. MAH kuj tsis tuaj yeem tshwj xeeb rau no. Nws muab cov cim ntawm kev rov qab thiab cov cim ntawm kev sib npaug ntau dua los ntawm cov cim ntawm kev rov qab. Qhov no yuav txog kev txawj ntsuam rau kev sib npaug ntawm cov ntaub, tab sis tsis txog kev txawj ntsuam rau kev sib npaug ntawm cov ntaub. Thaum peb saib rau cov cim ntawm kev txawj ntsuam, cov terpolymers no yuav rov qab thaum muaj kev rov qab ntawm qhov cim ntawm kev rov qab 20 thiab 30 percent tom qab cov binary copolymers tshwj xeeb. Thaum muaj qhov tsi zoo ntxiv: lawv tsis txog kev sib npaug ntawm cov plasticizer. Qhov no yog qhov tsi zoo rau qhov kev sib npaug ntawm cov plasticizer yog qhov tsi zoo rau kev sib npaug ntawm cov ntaub thaum muaj kev rov qab thiab kev rov qab.

Kuaj xyuam rau cov khoom tshiab tom qab kuaj xyuam nrog Aziridines lossis Polyisocyanates: Paub txog kev nyab xeeb >140°C

Thiab nyob rau hauv cov xwm txheej txaus siab uas cov khoom siv tau txais kev puas tsuaj ntau, qhov kev sib sau rau tom qab kev sib sau yuav ua cov cuab yeej 3D uas tsis tuaj yeem rov qab. Thaum peb plooj rau hauv qhov kev sib sau ntawd, cov aziridines yuav ua cov kev sib sau ntawm cov amine tshiab thiab cov hydroxyl groups ntawm PVA, thaum li cas cov polyisocyanates yuav ua cov kev sib sau ntawm urethane uas muaj zog ntau. Yog li cas ces cov cuab yeej no yog txaus siab? Nws tuaj yeem tswj cov kev rov qab ntawm cov kab laug thaum nws tau txais kev ntxiv ntev rau hauv 160 degrees Celsius. Thaum nws tau txais kev ntxiv ntev dua li 180C, nws tsuas loss 5% ntawm nws lub hluav tais tes, thaum li cas cov khoom siv tshwj xeeb yuav loss 25%. Thiab no yog qhov txaus siab: cov khoom siv no yuav tswj tau nws lub cev zoo li, tso cia nws muaj zog peeling 8 Newtons per centimeter thaum nws tau nyob rau hauv 150C rau 500 teev. Yog li, muaj qhov kev sib twg rau hauv qhov zog ntsuas, tab sis cov neeg tshaj lij tau pom tias cov khoom siv no tuaj yeem siv rau hauv cov roj tsiam thiab cov roj tsiam uas cov khoom siv yuav tsum tau txais kev ntxiv ntev thiab kev ntxiv ntev ntau dua tsis tau rov qab.

Tsim Kev Tswj Hwm Qhov Paub: Qhov Sib Txawv Rau Lub Cej Ntawm Qhov Khiav Tau, Qhov Tshuaj Ntawm Qhov Tshuaj Ntawm Qhov Tshuaj, thiab Qhov Khiav Tau

Yog li ua kom PVA adhesives muaj thermal stability zoo dua, ces yuav tsum xaiv cov lus uas yuav tsum txhawj xeeb rau ob peb qhov kev sib koom ntawm cov lus no. Thaum peb txhawj kom cov cross link density siab dua, nws yuav pab rau adhesive kom tuaj tsis tau rau cov cim txias uas siab dua 140 degrees Celsius, tab sis qhov no kuj muaj qhov tshwm sim. Cov molecules tsis tuaj yeem hloov hluas raws li yuav tau, thiab qhov no yuav pab los ua rau cov glue tsis muaj kev nyuaj siab thiab tsis tuaj yeem muaj kev nyuaj siab rau cov khoom sib txawv. Cov silica nanoparticles yog qhov zoo heev rau kev ua thermal barriers, tsis muaj kev dub dub. Tab sis lawv kuj ua rau cov mixture nyuaj dua, thiab yog ib zaug los yog ob zaug los yog peb zaug nyuaj dua. Qhov no yuav tsum muaj cov khoom sib txawv rau kev siv cov khoom no. Thaum muaj cov boron based cross linkers, lawv yuav ua rau cov kev nyuaj siab ntawm cov ntaub ntawv uas muaj kev nyuaj siab thiab tsis muaj qhov nyuaj siab rau cov ntaub ntawv, thiab yuav ua rau cov kev nyuaj siab nyuaj dua ntawm 15% thiab 30%. Qhov no yog qhov nyuaj heev rau cov neeg siv cov khoom sib txawv.

Kuam ntsuas cov lus qhia yog qhov tseem ceeb rau kev sib thaj ntawm cov khoom thiab qhov uas lawv yuav tsum ua haujlwm nyob rau hauv kev sib tw, tsis yog kev nrhiav qhov tshuab uas tuaj yeem siv rau txhua yam. Piv txwv li, kev sib hlub rau lub roj tsis tau yuav tsum muaj zog rau kev kub siab heev thaum sib tw, tab sis yuav tsum muaj zog rau kev siv, thiab qhov no yuav tsum muaj zog rau kev siv. Tsis zoo li kev sib hlub rau cov khoom siv, vim tias cov neeg siv khoom siv xav tau qhov uas lawv yuav tsum siv tau yooj yim thiab yuav tsum muaj zog rau kev siv tau ntev rau hauv kev siv khoom. Thaum cov neeg tswj hwm sib thaj raws li cov thawj chaw, cov khoom siv, thiab cov kev siv khoom rau hauv kev siv khoom, qhov no yuav pab tshem tawm cov teeb meem uas yuav tsum ua kom zoo thaum cov khoom siv tau txais kev kub siab heev rau hauv kev siv khoom nyob rau hauv qhov kev siv khoom.

FAQ Qeb

Puas yog qhov PVA adhesives tshwj xeeb tsis ua haujlwm thaum kub siab dua 100°C?

Cov PVA adhesives tshwj xeeb tsis ua haujlwm thaum kub siab dua 100°C primarily rau qhov hydrogen bond breakdown thiab qhov chain mobility nce, uas ua rau loss of adhesive strength.

Qhov kub siab tshwj xeeb rau PVA adhesives yog dab tsi?

Cov thawv tshuaj ntsuas hluav taws xob rau PVA adhesives muaj qhov tshuaj ntsuas hluav taws xob uas ploj los ntawm 75–85°C thiab qhov tshuaj ntsuas hluav taws xob ploj los ntawm 200°C.

Yog li cas PVA adhesives yuav tau ua kom zoo dua los tsis txhob ploj rau qhov hluav taws xob siab?

PVA adhesives yuav tau ua kom zoo dua los ntawm cov khoom sib xyaw ib yam li cov khoom sib xyaw boron-based thiab nano-silica los ua kom zoo dua qhov hluav taws xob thiab qhov ua haujlwm ntawm kev sib xyaw.