磷酸酯功能单体对聚羧酸减水剂抗泥性能的影响

摘要

Polycarboxylate superplasticizer bearing phosphate group was synthesized by aqueous solution radical polymerization,using acrylic acid(AA),methyl allyl polyoxyethylene ether(HPEG) and 2-hydroxyethyl methacrylate phosphate(HEMAP)as monomers,hydrogen peroxide(H2O2)and ascorbic acid(Vc)as initiators,and thioglycolic acid as the chain transfer agent. The copolymer was characterized by FTIR and 1H NMR. In order to investigate the effect of phosphate functional monomer on anti-clay properties of polycarboxylate superplasticizer,the water reduction performance of the superplasticizer was investigated by fluidity tests. The interlayer spacing of montmorillonite modified with superplasticizer was measured by X-ray diffraction(XRD). Adsorption of water reducing agents on cement and montmorillonite were measured by Total Organic Carbon(TOC)analyzer. The results showed that the fluidity of cement paste can exceed 275mm after 2h,when the dosage of superplasticizer was 0.20% of cement mass and the content of montmorillonite was 2% of cement.Compared with the interlayer spacing of montmorillonite treated with pure water,the interlayer spacing of montmorillonite treated with polycarboxylate superplasticizer containing phosphate did not change significantly and the side chains of the superplasticizer did not intercalate into the interlayer of montmorillonite. The adsorption process of polycarboxylate superplasticizer with phosphate group on montmorillonite was in accordance with the quasi-second-order adsorption kinetic equation. Phosphate ester group competed with carboxyl group for adsorption,which effectively weakened the adsorption of carboxyl group on montmorillonite.%通过水溶液自由基聚合法,以2-羟乙基甲基丙烯酸酯磷酸酯(HEMAP)为功能单体,以丙烯酸(AA)、甲基烯丙基聚氧乙烯醚(HPEG)为原料,过氧化氢(H2O2)/抗坏血酸(Vc)为引发剂,巯基乙酸为链转移剂,合成了一种含有磷酸酯基的聚羧酸减水剂.采用红外光谱(FTIR)、核磁共振氢谱对减水剂进行结构表征,通过水泥净浆流动度测定其减水性能,采用X射线衍射(XRD)测定蒙脱土吸附减水剂后的层间距,采用总有机碳(TOC)分析仪测定水泥和蒙脱土对减水剂的吸附量,探究磷酸酯功能单体对聚羧酸减水剂抗泥性能的影响.结果显示:当减水剂掺量为0.2%、蒙脱土掺量为1%时,水泥浆体2h流动度为275mm.与纯水处理蒙脱土的层间距相比,用含有磷酸酯基的聚羧酸减水剂处理过的蒙脱土的层间距变化不大,减水剂侧链未插入蒙脱土层间.蒙脱土吸附含磷酸酯基的聚羧酸减水剂的过程符合准二级吸附动力学方程,磷酸酯基与羧基存在竞争吸附,有效减弱了蒙脱土对羧基的吸附作用.