Researches On MPEG-AA-UDA Terpolymer Type Of Polycarboxylate Superplasticizer

Polycarboxylate superplasticizer which exhibited an excellent ability of water- reducing, preventing slump loss with duration of time and friendly to environment, has become ideal chemical admixture used in high performance concrete preparation and important infrastructure constructions, and has great development potentials.In this thesis, methoxy polyethylene glycol acrylate macromonomer was synthesized by esterification reaction with methoxy polyethylene glycol(n=23) and acrylic acid as main materials, under presence of inhibitor and catalyst. Study was carried out on effects of inhibitor type and amount, molar ratio of AA to MPEG, solvent amount, esterification temperature and reaction time on esterification ratio and performance of polycarboxylate superplasticizer. The optimal esterification proportion and process condition were determined. Based on design of molecular structure, terpolymer type of polycarboxylate superplasticizer (MPEG-AA-UDA) which had groups of carboxylic, sulphonic and polyoxyethylene was synthesized by radical polymerization in aqueous system with MPEG-AA macromonomer, unsaturated dicarboxylic acid and sodium methallyl sulfonate under existence of initiator. Each factor effecting on properties of MPEG-AA-UDA was discussed. By employing orthogonal testing analysis, the optimal proportion of copolymer monomer and dosage of initiator were determined.By using infrared spectrum and laser multi-angle scattering, the functional groups and molecular weight of MPEG-AA-UDA were determined. It was proved that copolymerization product had expected functional groups and narrow molecular weight distribution, its Mw was 1.38×105g/mol and Mn was 4.27×104g/mol. Then the ideal molecular structure of MPEG-AA-UDA had been obtained based on reagent proportion. Combined with results of zeta potential and hydration heat of cement, the water-reducing mechanism was investigated.Application properties of MPEG-AA-UDA in cement, mortar and concrete were tested and compared with other kinds of polycarboxylate superplasticizer. Experimental results showed that MPEG-AA-UDA exhibited significant retarding effect, high water-reducing rate, and good performance of dispersion and dispersion maintenance. The synthesized terpolymer had satisfying compatibility with different kinds of cement and good stability of storage.