Preparation Of Polycarboxylate Superplasticizer With Different Topologies And Its Application Study

With the rapid development of concrete industry, the application of polycarboxylate superplasticizer is more and more extensive. With small adding amount,environmental protection and other advantages, polycarboxylate superplasticizer was widely used. In concrete, compared with other polycarboxylate superplasticizer,adding polycarboxylate superplasticizer water-cement ratio can be significantly reduced, is still relatively high fluidity, and therefore improve strength.Polycarboxylate superplasticizer can provide excellent dispersion performance through the electrostatic repulsion of the main chain and the steric hindrance effect of the side chain, and the spatial effect is closely related to the skeleton structure.In this paper, different polymerization methods were used to controlling the molecular structure, and different structure polycarboxylate superplasticizer were synthesized to be investigated the effect of the structure on the properties.1.(TEA-Br(3)) was prepared by polymerizing triethanolamine (TEA) and 2-bromo-isobutyryl bromide (BIBB). By atom transfer radical polymerization,TEA-Br(3) -PHEMA-AA was prepared in polymerization of hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) using CuBr1 / 2,2-bipyridine as catalyst system. (EG-Br (2) -PHEMA-AA) was replaced with ethylene glycol (EG) in the same way. By atom transfer radical polymerization, polycarboxylate superplasticizer(EG-Br(2)-PHEMA-AA) was synthesized in polymerization of hydroxyethyl methacrylate (HEMA), acrylic acid and EG-Br(2). The optimum degree of polymerization and reaction time of star-shaped polycarboxylate superplasticizer(TEA-Br(3) -PHEMA-AA)were determined by the fluidity of cementpaste. Compared with comb-type polycarboxylate superplasticizer (EG-Br (2)-PHEMA-AA),the star polycarboxylate superplasticizer had higher fluidity of cement paste and compressive strength of 7d star polycarboxylate superplasticizer increased by 9-10%.2.Four-arm initiator (PER-Br(4)) was synthesized by polymerizing of pentaerythritol(PER) and bromo-isobutyryl bromide (BIBB). By atom-free radical polymerization,PER-Br(4)-PHEMA-AA was prepared by polymerization of hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) using CuBr1 / 2,2-bipyridine as catalyst system. The results show that the four-arm polycarboxylate superplasticizer is successfully synthesized, and the optimum reaction time and degree of polymerization were determined by the fluidity of cement paste. Compared with the star-shaped polycarboxylate superplasticizer,the dispersant system had better dispersibility,and at 7d days, concretecompressivestrength of four-arm polycarboxylate superplasticizer increased by 3-4%.3.Xylitol (MTC) and acryloyl chloride were used as reactants and N-N dimethylformamide (DMF) as solvent to prepare xylitol acrylate (AMTC). Under the initiator of ammonium persulfate, Hydroxyethyl acrylate (HEMA), acrylic acid (AA)and methylallyl polyoxyethylene ether (TPEG) were polymerized by free radical polymerization in order to synthesized xylitol modified polycarboxylate superplasticizer. The results showed that xylitol acrylate and xylitol modified polycarboxylate superplasticizer were successfully prepared, and the optimal synthesis conditions were investigated in the terms of the amount of xylitol acrylate,reaction temperature, reaction time and initiator. Compared with comb-typed polycarboxylate superplasticizer, there is better fluidity and at 7d stages, concrete compressive strength increased by 11-12%.