官能团接枝位点对聚羧酸减水剂性能的影响

The Influence of Functional Group Grafting Sites on the Performance of Polycarboxylate Superplasticizers

文中旨在阐明官能团接枝位点对聚羧酸系高性能减水剂(PCE)分散性能、吸附行为和分子构象的影响,合成了两种β-环糊精改性的PCE,其中一种被命名为(β-M)_(n)-AA-HPEG,β-CD接枝在其分子的主链上;另一种侧链末端接枝β-CD则称为PAA-g-(β-P)_(n)HPEG。与未经β-CD改性的聚羧酸系高性能减水剂(PAA-g-HPEG)相比,PAA-g-(β-P)_(n)HPEG和(β-M)_(n)-AA-HPEG在水泥浆体/含泥水泥浆体中均具备更佳的分散性能。官能团的接枝位点显著影响PCE的分子构象、水泥颗粒/黏土颗粒对其的吸附行为。吸附测试结果表明,主链作为接枝位点能有效提高水泥颗粒对PCE的饱和吸附量,降低黏土颗粒的表面吸附。以侧链末端为接枝位点时,引入的β-CD会略微降低水泥颗粒对PCE的饱和吸附量,但能够有效地阻止黏土颗粒对PCE的吸附。动态光散射的测试结果表明,与主链相比,侧链末端作为接枝位置能更有效地提高PCE的水动力学半径,不同接枝位点的β-CD通过不同方式提升了PCE的分散性能和抗黏粒性能。

This study aims to elucidate the effects of functional group grafting sites on the dispersion,adsorption behavior,and molecular conformation of polycarboxylate superplasticizer(PCE).Two types ofβ-cyclodextrin modified PCE were synthesized.One of them is named(β-M)_(n)-AA-HPEG,andβ-CD is grafted onto the main chain.Another one withβ-CD grafted on the side chain is called PAA-g-(β-P)_(n)HPEG.Compared with the PAA-g-HPEG withoutβ-CD modification,PAA-g-(β-P)_(n)HPEG and(β-M)_(n)-AA-HPEG have better dispersion performance in cement pastes/cement paste containing caly.The grafting sites of functional groups significantly affect the molecular conformation of PCE and adsorption behavior of cement particles/clay particles.The adsorption test results show that the main chain as grafting site can effectively increase the saturated adsorption amount on cement particle.When the end of the side chain as the grafting site,the introduction ofβ-CD slightly reduces the saturated adsorption capacity on cement particles,but can effectively prevent the adsorption by clay.And compared with the main chain,the side chain end as the grafting position can more effectively increase the hydrodynamic radius of PCE.β-CD at different grafting positions enhances the dispersion and clay tolerance in different ways.