Study On The Molecular Design And Performance Of Polycarboxylate-type Superplasticizers

The functional groups,acid anhydride and polyether macromonomers were used to reconstruct the backbone and long branches of polycarboxylate superplasticizers(PCE)by designing molecular structure in this paper.A series of PCEs with different molecular structure were synthesized at room temperature.The molecular structure,molecular weight and molecular weight distribution of the PCEs were analyzed by infrared spectroscopy(IR),high performance liquid chromatography(HPLC),gel permeation chromatography(GPC)and Zeta potential analysis.The effect of molecular structure on dispersibility and clay applicability of PCEs were discussed by the difference between the fluidity and the amount of adsorption on montmorillonite.Meanwhile the adsorption mechanism of PCEs with different molecular structures on montmorillonite were studied by the PCE amount of adsorption.The main research contents and innovation points are as follows:(1)The PCEs with different density of phospholipid and amide functional groups on the molecular backbone were synthesized via using acrylamide and unsaturated phosphate ester monomer to replace acrylic acid.We discussed the effects of newly introduced phospholipid and amide groups on the dispersion and adsorption properties of PCE.The results showed that the molecular weight distribution of novel PCEs were broadened and the distribution coefficient were 4.5 to 6.1.The initial dispersion of the amide type PCE to the cement slurry was good,and the phosphoester type PCE had good dispersibility of the cement paste containing montmorillonite.Both the amide and phospholipid types of PCEs had good anti-mud properties,and the adsorption capacity of PCEs on montmorillonite surface was less than that of ordinary PCE.When the PCE content was 0.2%,the fluidity value of phospholipid type PCE which 20% acrylic acid replaced by unsaturated phosphate ester monomer was still up to 275 mm after it was mixed with 3% montmorillonite cement slurry for 60 minutes.(2)The novel PCEs with hydrophobic group on the molecular long branches were synthesized by using propionic anhydride,butyric anhydride,succinic anhydride to esterify with ter minal hydroxyl groups of ?-hydroxy poly ethylene glycol(HPEG).The effect of long branches structure on the dispersion performance of cement was discussed.The results showed that the molecular weight distribution coefficient of the ter minal hydroxyl esterification type PCE were 4.16 to 4.79,but the dispersion property of PCEs was decreased.However the adsorption amount of PCEs which esterified with three kinds of acid anhydride on montmorillonite was small.When the PCE concentration was 0.2%,the adsorption capacity of succinic anhydride esterified PCE on the surface of montmorillonite was 4.3 mg/g,which was much lower than that of common PCE.The results indicate that the functional groups at the ter minal of PCE and their morphology affected the performance of PCE deeply.(3)In order to further explore the relationship between structure and function about PCE,three kinds of PCEs were synthesized by polyether isoprenyl oxy poly ethylene glycol ether(TPEG or IPEG),4-hydroxy butyl-poly ethylene glycol vinyl ether(VPEG)and HPEG.They all had good dispersibility to the cement slurry,and the molecular weight distribution coefficient was 4.51 to 5.31.The dispersion performance and flow retention of VPEG types PCE to montmorillonite-containing cement slurry was better.The adsorption of TPEG and VPEG types PCE on montmorillonite was close,while the adsorption amount of HPEG type PCE was high.The results indicated that the structure of long chain branch plays an important role in performance of PCE.