Study On Synthesis And Relationship Between Molecular Structure And Performance Of Ether-type Polycarboxylate Superplasticizer

Thanks to the good designability of molecular structure and predominant performancethe polycarboxylates high performance water-reducing admixture is highly praised by theconcrete construction engineering at all times. However, due to the initial research phase ofthe relationship between synthetic conditions, molecular structure and performance whichcauses certain troubles to improve the synthesis and application technologies, the preliminarydiscussion of influencing law of synthetic conditions on molecular structure and molecularstructure on performance is chiefly introduced in the paper. Then under the guide of the lawpolycarboxylate superplasticizer(PCA) is made and compared to the industrial sample onperformance.Polycarboxylate superplasticizer are synthesized under different process conditionsthrough free radical polymerization in aqueous solution, with redox initiating system asinitiator, with acrylic acid(AA) and methyl alkenyl polyoxyethylene polyoxypropyleneether(TPEG) as raw materials. The molecular structure is characterized by Ft-IR, GPC and~1HNMR, and effect of different synthetic conditions of PCA on the molecular structure is studied,then the performance is evaluated by cement paste, mortar and concrete. The result is shownas follows:1. Influencing law of synthetic conditions on molecular structure. polymerizationtemperature, titration time of reduce, initiator rate and adding quantity chiefly work on themolecular weight and molecular weight distribution. The adding quantity of chain transferagent has a great impact on the molecular weight. And the molecular weight and negative ioncharge density will gradually increase as the proportion of AA increases.2. Influencing law of molecular structure on performance. Within the molecularstructure limits characterized in this paper, dispersive performance of PCA is inverselyproportional to the molecular weight and negative ion charge density. The functional group-COOH majorly plays a big role on dispersive performance as-COOR majorly contributes toslump retaining. The dispersive properties of PCA become better and the slump retainingbecomes worse as the n(-COOH)/n(-COOR) gradually increases.3. Comparison of PCA and industrial samples. The sample A14-3which possesses better water reducing performance achieves a maximum mortar water reducing rate of38.97%,and the sample H12-3which has better slump retaining property reaches a maximumenlarging range of more than one times on cement paste mobility, which respectively has thebetter performance than the industrial samples.