Preparation And Properties Of Hyperbranched Polycarboxylic Acid Superplasticizer

Polycarboxylic acid superplasticizer is the latest generation of high-performance superplasticizer,which has the advantages of high water reduction rate,green environmental protection and strong molecular structure design.Hyperbranched polymer has a spherical-like spatial structure and a large number of functional groups on the surface,which have a great potential for modification.In this paper,hydroxy-terminated hyperbranched polymers were synthesized from diethanolamine,methacrylate and trimethylpropane,and a novel hyperbranched polycarboxylic acid superplasticizer was prepared by free radical reaction.The spatial steric hindrance of polycarboxylic acid superplasticizer was increased by using the larger spatial molecular structure of hyperbranched polymer,so as to improve the performance of polycarboxylic acid superplasticizer.Then the superplasticizer was tested macroscopically and characterized microscopically.The main research contents are as follows:(1)When the mole ratio of the acrylic acid,methyl allyl alcohol polyoxyethylene ether and methyl allyl sulfonate,is 3.5:1:0.3,the dosage of ammonium persulfate is 2%of the quality of methyl allyl alcohol polyoxyethylene ether,the reaction temperature is 75? and the reaction time is 4.5 h,the prepared polycarboxylic acid superplasticizer had the highest dispersion performance,and the fluidity of the cement paste reached 283mm.It was found that polycarboxylic acid superplasticizer was successfully synthesizeds by infrared spectrum.It improves the dispersion in cement particles through electrostatic repulsion by Zeta test.(2)When the mole ratio of synthesis of hydroxyl-terminated hyperbranched polymers,acrylic acid and methyl allyl alcohol polyoxyethylene ether is 3:13:2,synthesized hyperbranched polycarboxylic acid superplasticizer had the best dispersion properties,When it is compared with the unmodified hyperbranched polycarboxylic acid superplasticizer,the fluidity and retention of cement paste,the water reduction rate of cement mortar and the mechanical strength of cement mortar were improved.The dispersion of hyperbranched polycarboxylic acid superplasticizer is mainly due to steric hindrance while electrostatic repulsion only assists(3)The addition of hyperbranched polycarboxylic acid superplasticizer reduced the early heat generation of cement,inhibited the formation of calcium hydroxide,and delayed the cement hydration.At the same time,it promoted the formation of CSH gel,filled the gaps between cements,increased the compactness of the overall structure,and improved mechanical properties(4)The first generation of hyperbranched polymers and trimethylolpropane were iterated to synthesize hyperbranched polymers of different generations.The third generation hyperbranched polycarboxylic acid superplasticizer(G3)had the best performance.With the addition of 0.4%G3,the net slurry fluidity reached 318mm With the addition of 0.6%G3,the water reduction rate reached 33.4%,the compressive strength reached 28.3mpa,35.9mpa and 56.8mpa on 3d,7d and 28d,and the flexural strength reached 7.7mpa,8.2mpa and 8.8mpa,respectively,which significantly improved the mechanical strength of cement mortarFigure:[31],Table:[8],Reference:[100]...