Preparation And Properties Of Maleic Acid-type Superplasticizers

With the rapid development of the domestic construction industry,requirements for the performance of the concrete water-reducing agent becomehigher and higher. Because of the lower reducer water-reducing ratio of tradi-tional lignosulfonate water reducer and naphthalene water reducer, the largerslump loss of the fresh concrete and other issues, they have been difficult to meetthe needs of requirements of modern Construction industry. Due to its excellentdispersion and dispersed retention, the research on the polycarboxylate-typesuperplasticizer becomes the main developing trends at home and abroad. Thecurrent domestic study is mainly inclined to study the (meth)acrylate-typesuperplasticizer, while the research on the maleic acid-type superplasticizer israre. The synthesis of the polyethylene glycol (meth)acrylate monomer requireshigh temperature and long reaction time, but the yield is low and the toxicreagent toluene is used in the synthetic process too. The monomer must beseparated from the solvent after the reaction, and the residual toluene makes thesynthesized superplasticizer not meet the needs of safety and environmentalprotection. The polyethylene glycol maleic acid monomer is synthesized with themerits of short reaction time, high yields and environmental protection.Therefore, I mainly did the following studies on the preparation and performanceof maleic acid-type polycarboxylic superplasicizer.1.The macromolecular monomer(MAPEG1000) was prepared firstly bymaleic anhydride(MA) and polyethylene glycol(PEG1000), and the yield ofesterification was determinated. The structure of esterification was characterizedby fourier transform infrared spectrometer(IR). The polycarboxylate terpolymersuper-plasticizer MAPEG-MA-SMAS was prepared by copolymerization ofesterification intermediate(MAPEG), methyl acrylate(MA) and sodium methallylsulfonate(SMAS), the copolymerization effects on performance of superplas-ticizer were researched. Relative molecule mass and its distribution of superplas-ticizer was measured by gel permeation chromatography(GPC), and themicrostructure of cement was characterized by scanning electron microscope(SEM).The results show that when the molar ratio of MAPEG to MA to SMASwas1.0:0.5:0.5, the polymerization reaction temperature was85℃, thepolymerization reaction time was7h, the dosage of initiator was12％of totalmonomer mass and the relative molecule weight of PEG was1000, thesuperplasticizer prepared under this condition would exhibit good performance.The initial fluidity of cement paste could reach325mm with1.0%percentagemass content of this superplasticizer. GPC showed that the mean molecularweight(M_w) and polydispersity M_w/M_nof the superplasticizer was15345and2.087. SEM showed the amount of macropors of cement added with thepolymerization reduce, and the crystals grow more integrated.2.The macromolecular monomer(MAPEG1000) was prepared firstly bymaleic anhydride(MA) and polyethylene glycol(PEG1000) and the yield ofesterification was determinated. The structure of esterification was characterizedby IR. The polycarboxylate terpolymer superplasticizer MAPEG-SAS-AM wasprepared by copolymerization of esterification intermediate(MAPEG), sodiumallylsulphonate(SAS) and acrylamide(AM). The copolymerization effects onperformance of superplasticizer were researched.Relative molecule mass and itsdistribution of superplasticizer was measured by GPC and the microstructure ofcement was characterized by SEM.The results showed that when the molar ratio of MAPEG to SAS to AMwas1.0:1.5:1.5, the polymerization reaction temperature was85℃, thepolymerization reaction time was8h, the dosage of initiator was9%of totalmonomer mass and the relative molecule of PEG mass was1000, thesuperplasticizer prepared under this condition would exhibit good performance.The original fluidity of cement grout could reach305mm with1.0%percentagemass content of this superplasticizer. GPC showed that the mean molecularweight and polydispersity M_w/M_nof the superplasticizer was6754and2.156.SEM showed the amount of macropors of cement added with the polymerizationreduce and the crystals growed more dense.