酯化大单体酸醇比对聚羧酸减水剂性能影响

Effect of Esterification on the Performance of Polycarboxylic Acid Superplasticizer

聚羧酸减水剂主要是大单体和不饱和酸类小单体直接进行自由基共聚制备,主要通过改变合成工艺条件对减水剂进行性能优化,很少研究大单体对减水剂性能的影响。本实验从酯化大单体出发,通过合成不同酯化率的大单体制备聚羧酸减水剂,从而研究酯化大单体对聚羧酸减水剂性能的影响。以聚乙二醇和丙烯酸为原料,通过改变酸醇摩尔比制备出不同酯化大单体,再与丙烯酸和丙烯磺酸钠进行自由基聚合,制备出聚羧酸减水剂。研究酸醇摩尔比和减水剂添加量对酯化大单体的酯化率、聚羧酸减水剂的减水率、砂浆流的动性和水泥砂浆抗压强度的影响。结果表明:酸醇摩尔比3∶1,反应时间6h,制备的大单体酯化率达到94.38%;羧酸减水剂在1%掺量时,减水率达到28.3%,与空白样相比,3d和28d抗压强度比分别为177%和143%。通过红外光谱、XRD、SEM等对聚羧酸减水剂的减水机理进行研究,发现聚羧酸减水剂提高了水泥颗粒的分散性,减少了用水量;减水剂分子填充了水泥颗粒的缝隙,促进了晶体生长,提高了抗压强度。

Polycarboxylic acid superplasticizer is mainly prepared by direct free radical copolymerization of large monomers and small monomers of unsaturated acids,which mainly optimizes the performance of the superplasticizer by changing the synthesis process conditions,and rarely studies the influence of large monomers on the performance of the superplasticizer.In this study,the esterified macromonomer was synthesized to prepare polycarboxylic acid superplasticizer by synthesizing macromonomers with different esterification rates,so as to study the effect of esterified macromonomer on the performance of polycarboxylic acid superplasticizer.Polycarboxylate and acrylic acid were used as the raw materials to prepare different esterified macromonomers by changing the molar ratio of acid to alcohol,which were further polymerized with acrylic acid and sodium acrylate to produce polycarboxylate superplasticizer.The effects of molar ratio of acid to alcohol,esterification rate of water reducer dosage on esterified macro-monomers,water reducing rate of polycarboxylate superplasticizer,mobility of mortar flow as well as compressive strength of cement mortar were studied.The results showed that the molar ratio of acid to alcohol was 3∶1,the reaction time was 6 hours,and the esterification rate of the prepared monomer reached 94.38%.In contarst,when the content of carboxylic acid superplasticizer was 1%,the water reduction rate reached 28.3%.And compared with the blank sample,the compressive strength ratios of 3 days and 28 days were 177%and 143%respectively.Through the study on the water-reducing mechanism of polycarboxylate superplasticize by IR,XRD and SEM,it was found that polycarboxylate superplasticizer improved the dispersibility of cement particles and reduced the water consumption;The water reducing agent molecules filled the gaps of cement particles,promoted the growth of crystals and enhanced the compressive strength.