Study On The Synthesis And Properties Of Novel Polycarboxylate-Type Dispersants

Concrete is now the most large amount architectural engineering material. The cementwater reducer is one of modern concrete essential components. As polycarboxylic acid typewater-reducers exhibit an excellent ability of water-reducing and prevention of slump loss,their development has been being widely paid attention to. Polycarboxylicwater-reducers(Polycarboxylic acid water-reducers, abbreviated as PCA) is novel, which isproduced in large scale at abroad, while in our country the study of it still is at the laboratoryresearch stage.In this dissertation, a series of macromers of poly (ethylene oxide) monoacrylate andpolycarboxylic water-reducers had been synthesized and tested for properties.The high quality macromers bearing with polyoxyethylene groups (PEO) were producedby the esterification reaction of polyethylene glycol with the over-dosaged unsaturatedcarboxylic acid under a temperature of 70-120℃by adding a specified amount of sulfuricacid or p-methylbenzenesulfonic acid as catalyst. The reaction process was controlled bymeasuring the acidic value of reactants and calculating the harvest ratio of polyethyleneglycol's esterification. The further esterification of macromers was then restrained by quickcooling.Through the molecule design, a series of novel polycarboxylic acid type water-reducerswith a given structure were prepared by a copolymerization reaction under a certaintemperature in a water solution system from the polyethylene glycol unsaturated carboxylicacid esters and acrylic acid monomers with persulfate ammonium as a radical initiator. Thewater-reducing ratio of the production in concrete was 24.7% at the solid dosage of 0.45%.The water-reducing ratio of the production in concrete reached as high as 38.8% at the soliddosage of 1.0%.The slump offlowability of neat cement was maintained without any loss for2 hours, and after 3 hours, the slump of flowability of neat cement reached 280mm. At thesame time, the properties of compression strength and retarding action are better. PCA hasgone through the pilot tests, it will be widely used in the future.Dispersant is a primary additive, which plays an important role in the course ofproducing and application. Therefore, the polymeric dispersant is focused on in the field ofdispersant additive. In the dissertation, the synthesis and properties of novel polycarboxylate-type dispersantswere studied. PCA was synthesized through esterification, radical copolymerization andneutralization. The synthesis condition of PCA was discussed in esterification ratio, initiationagent's dosage, reaction ratio, reaction time, temperature, PEG's length, solution'sconcentration, and the production was tested in dispersing power and heat resisting property.The dispersity of PCA and traditional dispersing agents were compared in this paper. PCAhas better dispersity than the traditional ones.The two kinds of dispersive mechanism of PCA were also discussed in this dissertation.