Cov Kws Kho Mob Borida Tshuaj Ntsuam Xyuas Cov Txheej Txheem Ua Haujlwm Thiab Kev Npaj Txoj Cai Ntawm Polycarboxylic Acid Superplasticizer

Peb paub tias daim ntawv thov ntawm polycarboxylate superplasticizers hauv pob zeb engineering tau dhau los ua ntau dua. Piv nrog rau cov khoom siv superplasticizers xws li naphthalene sulfonate thiab sulfonated melamine formaldehyde condensates, polycarboxylate superplasticizers tuaj yeem muab siab dispersibility, fluidity, thiab stability rau lub dispersed system ntawm pob zeb ntawm tsawg npaum li cas, tiv thaiv slump poob. Tsis tas li ntawd, kev nce nqi ntawm cov khoom siv naphthalene, lub voj voog ntev ntawm naphthalene-raws li superplasticizers, thiab kev ua qias tuaj ib puag ncig ua rau daim ntawv thov ntawm polycarboxylate-based superplasticizers tseem ceeb. Tab sis koj puas paub cov txheej txheem ntawm kev txiav txim thiab kev npaj cov qauv ntawm polycarboxylate superplasticizers?

Muaj qee qhov kev tshuaj xyuas zoo ntawm kev tshawb fawb txog kev nce qib ntawm polycarboxylate superplasticizers, tshwj xeeb tshaj yog hais txog lawv cov qauv kev npaj, kev ua haujlwm, thiab lwm yam. Yog li ntawd, Borida caw cov kws tshaj lij los muab kev tshuaj xyuas txog kev tshawb fawb txog kev npaj cov ntsiab lus, kev ua haujlwm, thiab kev cia siab yav tom ntej ntawm polycarboxylate superplasticizers.

1. Kev Npaj Cov Cai ntawm Polycarboxylate Superplasticizers

Polycarboxylate-based high-performance superplasticizers yog macromolecular compounds nrog sulfonic pawg, carboxyl pawg, amino pawg, thiab polyoxyethylene sab chains. Lawv yog synthesized nyob rau hauv aqueous tov los ntawm dawb-radical copolymerization, ua ib tug comb-zoo li tus high-molecular-yuag surfactant.

Main raw khoommethacrylic acid, acrylic acid, ethyl acrylate, hydroxyethyl acrylate, sodium allylsulfonate, methyl methacrylate, methoxypolyethylene glycol methacrylate, ethoxylated polyethylene glycol acrylate, allyl ether, thiab lwm yam. Thaum lub sij hawm polymerization, ib tug initiators xws li water-soluble benzoate, benzoic acid, methacrylic acid. Azobisisobutyronitrile yog siv. Cov neeg sawv cev ntawm cov saw txuas muaj xws li 3-mercaptopropionic acid, mercaptoacetic acid, thiab isopropanol.

Synthesis method: Nyob rau hauv cov tshuaj tiv thaiv cov hlab uas nruab nrog ib tug neeg kho tshuab stirrer, tus pas ntsuas kub, thiab cov khoom xa me me, cov tshuaj monomer, cov tshuaj pib, thiab cov saw hloov cov tshuaj tov yog ntxiv dropwise. Thaum xaiv cov polymerization monomers, cov copolymerization reactivity ratios yuav tsum tau txiav txim siab tag nrho. Cov tshuaj tiv thaiv kub yog nyob ntawm hom monomers siv thiab feem ntau ntog hauv thaj tsam ntawm 0-60 degree . Cov tshuaj monomer yog ntxiv dropwise tshaj 1-2 teev, ua raws li qhov ntxiv 1- teev cov tshuaj tiv thaiv ntawm qhov kub thiab txias. Tom qab ntxiv dej rau neutralization, cov khoom raug tso tawm.

2. Mechanism of Action ntawm Polycarboxylate Superplasticizers

Polycarboxylate-based high-performance superplasticizers yog ib hom tshiab ntawm superplasticizer nrog ntau qhov zoo, txawm tias lawv qhov kev ua haujlwm tiag tiag tseem tsis nkag siab tag nrho. Nov yog qee qhov kev xav:

Retarding nyhuv: Cov pab pawg carboxyl ua raws li kev tiv thaiv kev tiv thaiv, tsim cov complexes nrog Ca²⁺ ions (R-COO⁻–Ca²⁺), txo cov concentration ntawm Ca²⁺ ions hauv kev daws, ncua sij hawm crystallization ntawm Ca(OH)₂, txo qhov tsim ntawm CHS gels, thiab yog li retarding lub hydration ntawm cement.

Polar pawg affinity: Carboxyl (-COOH), hydroxyl (-OH), amino (-NH₂), thiab polyoxyalkylene (-OR) n pawg muaj kev sib raug zoo nrog dej. Los ntawm cov teebmeem saum npoo av xws li adsorption, dispersion, ntub dej, thiab lubrication, lawv muab dispersibility thiab fluidity rau cov cement hais. Los ntawm kev txo cov kev sib txhuam ntawm cov cement hais thiab txo lub zog dawb ntawm cov cement-dej interface, lawv txhim khu kev ua haujlwm ntawm cov pob zeb tshiab. Ib txhij, polycarboxylate tebchaw adsorb mus rau cov cement hais qhov chaw, imparting tsis zoo nqi los ntawm carboxylate ions. Qhov no induces electrostatic repulsion ntawm cov hais, tiv thaiv lub siab nyiam rau cement paste rau flocculate (DLVO txoj kev xav) thiab ua rau thaj chaw sib cuag ntawm cov cement thiab dej, txhawb nqa tag nrho cov dej ntawm cov cement. Thaum lub sij hawm dispersion ntawm cov cement hais, cov dej daig hauv agglomerates raug tso tawm, txhim kho kev ua haujlwm thiab txo cov dej sib tov uas xav tau.

Steric cuam tshuam: Polycarboxylate molecules adsorb rau saum npoo ntawm cov cement hais nyob rau hauv ib tug comb-zoo li tus configuration, tsim ib tug adsorption txheej nyob rau saum npoo ntawm cov khoom gel. Thaum cov polymer adsorption txheej ntawm cov cement hais mus rau ib leeg, steric hindrance ntawm cov polymer chains tiv thaiv cov hais los ntawm agglomerating. Qhov no yog ib qho ntawm cov laj thawj tseem ceeb vim li cas polycarboxylate superplasticizers muaj qhov sib txawv zoo dua piv rau lwm lub tshuab.

Zeta muaj peev xwm thiab dispersion tuav: Lub dispersion retention mechanism ntawm polycarboxylate-based high-performance superplasticizers tuaj yeem nkag siab los ntawm kev soj ntsuam kev sib raug zoo ntawm kev sib xyaw lub sij hawm thiab zeta muaj peev xwm hauv cement paste. Feem ntau, cov pob zeb ua ke nrog naphthalene- lossis melamine-based high-performance superplasticizers qhia qhov poob qis tom qab 60 feeb, thaum cov pob zeb uas muaj polycarboxylate superplasticizers pom qhov poob qis dua. Qhov sib txawv no tshwm sim vim hais tias tus qauv adsorption ntawm superplasticizer thiab cement hais txawv. Kev sib cuam tshuam ntawm cov txheej txheem siab molecular-qhov hnyav adsorption thiab cov cement hais ua rau ob qho tib si steric thiab electrostatic repulsion, nrog me ntsis hloov hauv zeta peev xwm.

Kev tshawb fawb ntawm cov txheej txheem ntawm cov cement dispersion qhia tias DLVO txoj kev xav, uas piav qhia txog kev tawg ntawm ionic repulsion, feem ntau ua tsis tau raws li qhov kev sim. Cov nyhuv steric hindrance tau ua tiav piav qhia txog kev cuam tshuam ntawm polycarboxylate superplasticizers ntawm cov cement. Cov polymer adsorbs mus rau saum npoo ntawm cov cement hais, nrog rau sab chains txuas mus rau hauv cov tshuaj. Cov chains sab no tsim steric hindrance, tiv thaiv cov khoom los ntawm kev sib raug zoo, yog li ua kom lawv dispersion thiab stability. Qhov no mechanism yog dav txais niaj hnub no. Polymers nrog ntev sab chains muaj zeta muaj peev xwm thiab siab steric repulsion, uas ua rau dispersibility zoo heev. Txawm li cas los xij, qhov ntev ntawm cov saw ntev ntev yuav ua rau muaj kev cuam tshuam ntawm cov kab sib txuas ntawm cov khoom sib cais, ua rau cov khoom sib xyaw ua ke.