梳形聚羧酸超塑化剂在水泥颗粒表面的吸附行为

摘要

研究了吸附溶液体系温度、pH值和电解质浓度等对甲基丙烯酸-甲氧基聚乙二醇甲基丙烯酸酯(MAA-MPEGMA)梳形聚羧酸共聚物在水泥颗粒表面的吸附行为的影响.聚羧酸共聚物在水泥颗粒表面的吸附呈Langmuir等温吸附模型.吸附量随着温度的升高而降低,表明聚羧酸共聚物在水泥颗粒表面的吸附是一个放热反应.根据Clausius-Clapeyron方程计算吸附热为17.4 kJ/mol.聚羧酸共聚物在水泥颗粒表面的标准吸附自由能<0,吸附是自发的.吸附量随着体系pH值的增大、电解质浓度的增大而减小.红外光谱分析表明,聚羧酸共聚物在水泥颗粒表面的吸附是通过分子结构上羧基与Ca2+间的配合作用实现的,说明这种吸附是一种化学吸附.%The adsorption of poly (methacrylic acid-co-methoxypolyethylene glycol monomethacrylate) comb-type polycarboxylate superplasticizer (PCE) on cement particle surface has been studied as a function of temperature, pH, and electrolyte concentration. The adsorption amount of PCE is found to decrease with an increase of temperature, pH or concentration of electrolyte respectively. The adsorption isotherm of PCE exhibits Langmuirian behavior. The adsorption of PCE copolymer on cement particle is an exthothermal reaction. The adsorption heat is calculated to be 17.4 kJ/mol, by Clausius-Clapeyron equation. The adsorption Gibbs free energy ΔadsGo<0, which indicates the adsorption of PCE on cement is a spontaneous process. FTIR spectroscopic data provide evidence in support of surface complexation and chemical interaction formed by carboxylate functional groups -COO- of copolymers with Ca2+ on particle surface.