Crosslinking ntawmAdipic dihydrazide (ADH)thiabDiacetone Acrylamide (DAAM)koom nrog kev tsim ntawmcovalent bondsnruab nrab ntawm ob lub molecules, uas ua rau kev loj hlob ntawm apeb-dimensional network, feem ntau nyob rau hauv cov ntsiab lus ntawm polymer chemistry. Cov txheej txheem no muaj feem xyuam rau ntau yam kev siv, tshwj xeeb hauv kev tsim cov txheej txheem polyurethane, nplaum, thiab lwm yam ntaub ntawv nrog cov khoom siv kho kom zoo.
Txhawm rau nkag siab txog cov txheej txheem ntawm crosslinking, nws yog ib qho tseem ceeb rau thawj zaug tshuaj xyuas cov qauv tshuaj thiab cov pab pawg reactive tam sim no hauv ADH thiab DAAM, ua raws li qhov xwm txheej ntawm cov txheej txheem crosslinking nws tus kheej.
1. Chemical Structure thiab Reactivity ntawm ADH thiab DAAM
Adipic dihydrazide (ADH):Aryl diisocyanates yog cov organic tebchaw nrog ob pawg isocyanate (-NCO) txuas rau lub nplhaib uas muaj ntxhiab. Cov isocyanates no yogheev reactivethiab ua haujlwm tseem ceeb hauv kev sib txuas ntawm cov khoom siv polyurethane. Cov pab pawg isocyanate yog electrophilic thiab nkag siab nrog cov nucleophilic pawg xws li hydroxyl, amines, thiab lwm cov pab pawg ua haujlwm, ua rau lawv cov neeg sib tw tseem ceeb rau kev sib cuam tshuam.
Diacetone Acrylamide (DAAM):DAAM feem ntau yog hloov kho acrylate monomer uas muaj ahydroxyl pawg (-OH) thiab ib pawg acrylic. Hauv qee cov qauv, nws kuj suav nrog DMPA, uas yog pawg hydrophilic uas tuaj yeem pab txhawb kev sib cais hauv cov dej-raws li dej. Cov yam ntxwv tseem ceeb ntawm DAAM rau kev sib txuas sib txuas yog pawg hydroxyl (-OH), uas yog nucleophilic thiab tuaj yeem cuam tshuam nrog pawg electrophilic isocyanate.
2. Crosslinking Mechanism
Txoj kev sib txuas ntawm ADH thiab DAAM yog homcondensation tshuaj tiv thaiv, qhov twg ob lub molecules ua ke los ua ib tug loj, complex qauv nrog kev tso tawm ntawm ib tug me me molecule, feem ntau carbon dioxide (CO₂) los yog dej. Cov txheej txheem tshwj xeeb tuaj yeem piav qhia ib qib zuj zus:
ib. Cov tshuaj tiv thaiv ntawm Isocyanate thiab Hydroxyl Group
Thawj kauj ruam tseem ceeb tshaj plaws hauv cov txheej txheem crosslinking yog cov tshuaj tiv thaiv ntawm covisocyanate pawg ntawm ADH thiab pawg hydroxyl ntawm DAAM. Isocyanates yog cov reactive heev vim qhov polarized ntawm N = C = O daim ntawv cog lus. Thaum ADH thiab DAAM sib xyaw, pawg hydroxyl ntawm DAAM ua raws li nucleophile thiab tawm tsam cov electrophilic carbon ntawm pawg isocyanate. Qhov no tshwm sim nyob rau hauv lub tsim ntawm aurethane linkage (–NH–C(O)–O–)thiab tso tawm cov pa roj carbon dioxide (CO₂) raws li cov khoom lag luam. Cov kauj ruam no ua tau zoo tsim kom muaj kev sib raug zoo ntawm ob lub molecules.
b. Kev tsim ntawm Urethane Linkages
Thaum cov tshuaj tiv thaiv, pawg isocyanate los ntawm ADH reacts nrog hydroxyl pawg DAAM, tsim ib qhourethane (los yog carbamate) linkage. Cov kauj ruam no rov qab ua ntau yam DAAM molecules, txhua tus muaj ib pab pawg hydroxyl, hnov mob nrog cov pab pawg isocyanate ntawm ADH. Qhov tshwm sim yog tsim ib lub network ntawm interconnected urethane bonds, tsim ib tug crosslinked polymer network.
Cov tshuaj tiv thaiv dav dav rau kev tsim cov urethane daim ntawv cog lus yog:
Cov tshuaj tiv thaiv no yog exothermic heev thiab tuaj yeem txuas ntxiv mus ntev li ntev tau muaj cov pab pawg hydroxyl thiab isocyanate.
c. Ntxiv Crosslinking thiab Polymerization
Raws li cov tshuaj tiv thaiv tshwm sim, ntau pawg isocyanate los ntawm ADH tuaj yeem cuam tshuam nrog lwm pawg hydroxyl los ntawm DAAM ntxiv molecules, ua rau ntxiv polymerization thiab kev loj hlob ntawm kev sib txuas sib txuas. Tus naj npawb ntawm crosslinks hauv lub network polymer kawg yog nyob ntawm qhov piv ntawm ADH rau DAAM thiab cov xwm txheej cov tshuaj tiv thaiv.
d. Tsim kom muaj peb-dimensional Network
Raws li ntau thiab ntau DAAM molecules hnov mob nrog ADH, cov qauv ntawm cov khoom hloov los ntawm ib tug linear los yog branched polymer mus rau ib tugpeb-dimensional network. Qhov kev sib txuas sib txuas no yog qhov ruaj khov thiab tiv taus kev puas tsuaj, uas yog ib qho laj thawj vim li cas cov ntaub ntawv zoo li polyurethanes muaj txiaj ntsig zoo hauv cov txheej txheem, cov nplaum, thiab lwm yam kev siv. Lub xub ntiag ntawm DMPA-hloov acrylate qauv hauv DAAM kuj tso cai rau cov dej solubility lossis dispersibility, ua rau cov khoom kawg uas muaj peev xwm ntau yam rau cov dej-raws li formulations.
3. Cov yam ntxwv cuam tshuam rau txoj kev sib txuas
Ob peb yam cuam tshuam rau qhov twg thiab qhov ua tau zoo ntawm txoj kev sib txuas ntawm ADH thiab DAAM:
ib. Stoichiometry of ADH and DAAM
Molar ratio ntawm isocyanate pawg (ADH) rau hydroxyl pawg (DAAM) yogtseem ceeb heev rau kev tswj cov degree ntawm crosslinking. Yog tias qhov sib piv siab dhau ntawm ADH (piv txwv li, ntau cov isocyanates thiab tsis txaus hydroxyl), qee pawg isocyanate yuav nyob twj ywm, uas tuaj yeem ua rau tsis tiav crosslinking thiab txo cov khoom siv. Ntawm qhov tod tes, DAAM ntau dhau tuaj yeem ua rau hla dhau, uas tuaj yeem ua rau cov khoom tawg dhau.
b. Kub thiab sijhawm
Qhov kub thiab lub sijhawm tso cai rau cov tshuaj tiv thaiv kuj tseem ceeb heev. Cov tshuaj tiv thaiv ntawm isocyanates thiab hydroxyl pawg feem ntau tshwm sim ntawmKev kub siab (piv txwv li, 50 ° C txog 100 ° C), raws li qhov no accelerates tus nqi ntawm cov urethane tsim. Kev ncua sij hawm cov tshuaj tiv thaiv kuj tso cai rau kev ua tiav crosslinking ntau dua thiab cov khoom siv zoo dua.
c. Catalysts thiab Additives
Qee cov catalysts tuaj yeem siv rauua kom cov tshuaj tiv thaiv isocyanate-hydroxyl. Piv txwv li, hlau-raws li catalysts xws li tin (Sn) los yog amine-based catalysts tuaj yeem muab ntxiv los pab txhawb cov tshuaj tiv thaiv, txhim kho kev ua tau zoo thiab ceev ntawm crosslinking. Cov khoom siv ntxiv xws li stabilizers lossis plasticizers kuj tseem tuaj yeem suav nrog los hloov kho cov khoom kawg ntawm cov khoom.
4. Kev siv ntawm ADH-DAAM Crosslinked Polymers
Cov crosslinked polymers tsim los ntawm ADH thiab DAAM yog siv ntau yam kev siv, xws li:
- Polyurethane txheej:Cov ntaub ntawv no feem ntau siv rau hauv tsheb txheej, txheej txheej txheej, thiab kev tiv thaiv tiav, vim tias cov kab sib txuas sib txuas muab kev ua kom zoo dua qub, tshuaj tiv thaiv, thiab cov khoom siv kho tshuab.
- Adhesives thiab Sealants:Lub zog siab thiab adhesion zog ntawm cov kab sib txuas sib txuas ua rau lawv zoo tagnrho rau kev sib txuas cov ntaub ntawv hauv kev tsim kho, tsheb, thiab hluav taws xob.
- Cov khoom siv biomedical:Crosslinked polymers feem ntau yog siv rau hauv cov khoom siv tshuaj biomedical thiab kev xa tshuaj, qhov uas tswj kev tso tawm thiab biocompatibility tseem ceeb heev.
Lub crosslinking mechanism ntawmADHthiabDAAMkoom nrog cov tshuaj tiv thaiv ntawm cov pab pawg isocyanate nrog cov pab pawg hydroxyl los tsim cov urethane linkages, ua rau kev tsim cov kab sib txuas,Peb-dimensional polymer network. Cov tshuaj tiv thaiv no tau cuam tshuam los ntawm ntau yam xws li stoichiometry, kub, thiab catalysts, thiab nws yog dav siv hauv kev tsim cov ntaub ntawv uas xav tau txhua yam, thermal, thiab tshuaj lom neeg. Lub versatility thiab lub zog ntawm qhov tshwm sim crosslinked network ua rau cov ntaub ntawv tseem ceeb nyob rau hauv ntau yam kev siv.
Post lub sij hawm: Jun-12-2025