Molecular Structure Ntawm Polycarboxylic Superplasticizer

Cov qauv molecular ntawm polycarboxylic superplasticizers muaj cov yam ntxwv hauv qab no: pawg polar muaj zog xws li carboxyl, sulfonic, thiab polyethylene oxide pawg tau nkag mus rau hauv cov saw tseem ceeb lossis sab, muab cov molecules zoo li cov qauv. Feem ntau, nws nthuav tawm cov qauv qhia hauv daim duab 1, qhov twg tus neeg sawv cev ntawm cov tshuaj formula yog kev sib xyaw ntawm qee qhov chaw, nrog rau M1 thiab M2 sawv cev H thiab alkali hlau ions, raws li; M3 sawv cev rau H, alkali hlau ammonium ions, los yog organic amines. Nyob rau hauv cov cement paste system, cov saw ntev ntev macromolecules sib cuam tshuam nrog ib leeg los ntawm hydrophilic sab chains thiab encapsulate cement hais, thaum cov pab pawg hydrophobic ntsib cov tshuaj aqueous. Yog li ntawd, superplasticizer molecules dissociate mus rau hauv loj anions nyob rau hauv dej uas adsorb mus rau saum npoo ntawm cement hais, txo lawv lub zog nto. Qhov no ua rau muaj zog hluav taws xob nyob rau saum npoo ntawm cov cement hais, ua kom muaj txiaj ntsig zoo ntawm zeta muaj peev xwm, yog li tsim kom muaj zog electrostatic repulsion ntawm cov khoom, uas cuam tshuam los yog cuam tshuam qhov tsim ntawm cov qauv cohesive ntawm cov cement gel, ua rau muaj zog electrostatic repulsion. txheeb ze nce nyob rau hauv tus nqi ntawm cov dej dawb thiab ua ib tug dispersive nyhuv. Tsis tas li ntawd, lub adsorptive txheej ntawm siab polymers tsim spatial barriers rau particle aggregation.

Los ntawm daim duab, nws tuaj yeem pom tias cov qauv tshuaj ntawm polycarboxylic superplasticizers yog ntawm hydrophilic qaum-hydrophobic sab saw hom. Nws yog tus cwj pwm los ntawm kev muaj carboxylate anionic sab chains ntawm lub davhlau ya nyob twg ntawm cov saw tseem ceeb thiab cov tsis-ionic sab chains hauv nruab nrab. Nyob rau hauv tib lub macromolecule, muaj ob qho tib si anionic thiab non-ionic sab chains, ua rau nws yog ib qho kev sib xyaw ionic hom additive nrog ntau lub cev thiab tshuaj. Lub hydrophobicity ntawm ntau pawg hydrophobic tuaj yeem suav tau raws li hauv qab no: aliphatic alkanes Ntau dua lossis sib npaug rau cycloalkanes > aliphatic aromatic hydrocarbons > aromatic hydrocarbons > hydrocarbons nrog pab pawg tsis muaj zog hydrophilic. Thaum cov pab pawg hydrophobic yog aliphatic alkanes, qhov nce ntawm cov pa roj carbon atoms hauv cov saw hlau hydrophobic tseem ceeb txhim kho lub peev xwm los txo cov dej ntws tawm. Rau cov pab pawg hydrophilic, qhov kev ua tau zoo ntawm superplasticizer feem ntau cuam tshuam los ntawm lawv qhov ntim, qhov chaw txheeb ze, thiab qhov ntau: qhov loj ntawm pawg hydrophilic cuam tshuam rau thaj tsam ntawm cov superplasticizer molecules nyob rau hauv cov txheej txheem adsorptive, yog li cuam tshuam lub peev xwm los txo qhov nro. . Thaum cov pab pawg hydrophilic nyob rau hauv qhov kawg ntawm cov pa roj carbon saw, lawv muaj txiaj ntsig zoo ntawm kev txo qhov nro, thaum muaj ntau pawg hydrophilic ua rau kev ua haujlwm zoo dua. Tsis tas li ntawd, qhov ntev thiab qhov ntau ntawm cov saw hlau sab cuam tshuam cuam tshuam rau kev ua haujlwm ntawm cov dej-txo cov superplasticizer. Thaum muaj ntau txoj hlua ntev ntev, lawv txuas mus rau hauv qhov chaw, tsim steric hindrance uas zoo tiv thaiv kev sib cuag ntawm cov cement hais. Hloov pauv, thaum muaj ntau cov hlua txuas luv luv, lawv cov adsorption tus nqi siab dua.

Qhov no tuaj yeem nkag siab tau raws li hauv qab no: raws li cov qauv zoo li comb ntawm carboxylic acid series, ib qho ntxiv ntawm cov saw hlau uas muaj sulfonic acid pawg, uas tau los ntawm ternary copolymerization ntawm unsaturated hydrocarbons uas muaj carboxyl thiab sulfonic acid pawg thiab unsaturated. hydrocarbons uas muaj ether, ester, los yog amide bonds. Cov sulfonic thiab carboxylic acids nyob rau ntawm ib sab saw, thaum ether, ester, los yog amide bonds nyob rau lwm sab saw, tag nrho cov pab mus rau ib tug structural unit. Cov saw tseem ceeb yog cov saw hlau carbon-carbon, thiab cov saw hlau sab uas muaj cov sulfonic acid pawg kuj tuaj yeem yog cov saw hlau carbon-carbon lossis lub nplhaib benzene. Cov pab pawg sulfonate ntawm sab saw thiab pawg carboxylate muaj nyob ua ntu anionic, nrog cov anions nyob rau ntawm qhov kawg ntawm cov saw hlau. Cov pawg carboxyl uas muaj nyob hauv cov kua qaub yog ib pawg tseem ceeb rau kev sib txuas ntawm hydrogen. Cov pab pawg tsis tseem ceeb uas muaj peev xwm tsim cov ntawv cog lus hydrogen muaj nyob rau hauv daim ntawv ntawm ether, ester, lossis amide bonds thiab tsim cov ntu uas tsis yog ionic. Kev sib koom ua ke ntawm anionic thiab non-ionic pawg nyob rau hauv tib lub molecule ua rau muaj kev hloov pauv tau zoo sib xyaw ionic hom additive. Ntawm cov pab pawg ua haujlwm no, COOH thiab SO₃H nthuav tawm cov khoom tshwj xeeb hauv polycarboxylic superplasticizers thiab ua lub luag haujlwm tseem ceeb thaum lub sijhawm thov: lub luag haujlwm tseem ceeb ntawm SO₃H yog muab kev sib cais siab thiab ua tiav cov dej txo qis, uas ua rau retardation thiab txij nkawm. poob; Lub luag haujlwm tseem ceeb ntawm COOH yog txhawm rau tshem tawm cov khoom siv cement zoo thiab ncua sijhawm cov tshuaj tiv thaiv dej ntawm cov cement. Tsis tas li ntawd, cov pab pawg ua haujlwm xws li amide thiab carboxyl pawg tuaj yeem ua rau hydrolysis nyob rau hauv ib puag ncig alkaline, tso qis molecular hnyav hydrolysis cov khoom uas muaj dej-txo cov teebmeem, yog li ua tiav cov txiaj ntsig xav tau. Cov yam ntxwv ntawm cov molecules endow polycarboxylic superplasticizers nrog adsorption-dispersion ua, nrog rau ntub dej thiab lubricating zog.