Abstract

By the esterification of benzoic anhydride (BA) with polyoxyethylene ether (HPEG), the modified macromonomer (BA-HPEG) with benzoate of HPEG was prepared. Then, BA-HPEG and HPEG were copolymerized with acrylic acid (AA) with an alkyd ratio of 2:1 to obtain three novel polycarboxylate superplasticizer BA-PCE-10, BA-PCE-20 and BA-PCE-30 with good flow retaining behaviors of cement mortars. The effects of the benzoate content in the copolymers on adsorption, dispersion, Zeta potential and hydrodynamic radius for cement suspensions were investigated to elucidate the governing dispersing mechanism. The absorption of the modified copolymers on the cement surfaces was controlled by COO^― and hydrophobic phenyl content in copolymers and polymer conformation in solution. The fluidity of cement slurry increases with the adsorbed amount to increase dispersion effect. The copolymers grafted with benzoate exhibited a high dispersion performance than that of the unmodified molecule, which could be explained as the hydrophobic modified polycarboxylate superplasticizer mainly dispersing cement particles by the main repulsion of steric hindrance and electrostatic repulsion, so as to improve the dispersion performance of cement. The study shows that the flow retaining behaviors of polycarboxylate superplasticizer can be significantly improved by BA modified with hydroxyl-terminated of the side chains of polycarboxylic superplasticizer.

摘要

通过苯甲酸酐(BA)与聚氧乙烯醚(HPEG)的酯化反应，制备了HPEG的苯甲酸酯改性大分子单体(BA-HPEG)。然后，将BA-HPEG和HPEG与丙烯酸（AA）以2:1的醇酸比共聚，得到三种具有良好流动保持性的新型聚羧酸减水剂BA-PCE-10、BA-PCE-20和BA-PCE-30水泥砂浆的行为。研究了共聚物中苯甲酸酯含量对水泥悬浮液的吸附、分散、Zeta 电位和流体动力学半径的影响，以阐明控制分散的机制。改性共聚物在水泥表面的吸收由 COO 控制^―共聚物中的疏水性苯基含量和溶液中的聚合物构象。水泥浆的流动性随着吸附量的增加而增加，从而增加分散效果。接枝苯甲酸酯的共聚物表现出比未改性分子高的分散性能，这可以解释为疏水改性聚羧酸减水剂主要通过空间位阻和静电排斥的主要排斥分散水泥颗粒，从而提高分散性能。水泥。研究表明，聚羧酸减水剂侧链羟基封端的 BA 改性可以显着改善聚羧酸减水剂的流动保持性能。