聚丙烯酸钠的阻垢、缓蚀机理研究

【作者】 夏笑虹；

【导师】 李国希；

【作者基本信息】 湖南大学 ， 材料学， 2001， 硕士

【摘要】 本文采用电子自旋共振技术、漫反射红外光谱技术以及化学、电化学方法研究了聚电解质聚丙烯酸钠的阻垢、缓蚀机理。 用过硫酸铵作引发剂合成了低分子量的聚丙烯酸钠，采用哌啶氮氧自由基对它进行标记。标记聚丙烯酸钠的ESR谱高场处的峰高明显比纯自由基的低，这是由于标记的氮氧自由基运动受到聚合物长链的束缚。 在聚丙烯酸钠的阻垢机理研究中，静态阻垢实验的结果表明聚丙烯酸钠对磷酸钙、碳酸钙、硫酸钙都有一定的阻垢效果，阻垢率随聚丙烯酸钠浓度的增加而增加。用电子自旋共振技术通过计算吸附链节分数（p）研究聚丙烯酸钠的吸附构型；用漫反射FT-IR红外技术确定它的吸附基团。研究表明聚丙烯酸钠通过在水中电离出羧酸根负离子与垢物表面的正电荷由于异性电荷吸引而吸附在垢物微晶粒表面，吸附分子中大部分链节固着在垢物表面，少部分链节以链环或链尾的形式伸向溶液。形成的吸附层覆盖了垢物生长的活性点，使之无法长大，并且使已形成的垢物微晶粒表面带上同种电荷而相互排斥，最终悬浮分散在水中。 在聚丙烯酸钠的缓蚀机理研究中，静态失重实验的结果表明聚丙烯酸钠对碳钢有一定的缓蚀作用，缓蚀率随聚丙烯酸钠浓度的增加而缓慢增加。对碳钢在含有高硬水中的极化曲线和交流阻抗图谱的分析得出聚丙烯酸钠加入前后碳钢的腐蚀电位(E_corr)没有移动（约-760mV），传递电阻有所增大，说明聚丙烯酸钠只是吸附在金属表面起着覆盖作用，使腐蚀反应只能在没有被聚丙烯酸钠所覆盖的表面进行。电子自旋共振技术和漫反射FT-IR红外技术的研究结果表明，聚丙烯酸钠在金属腐蚀产物（羟基氧化铁、三氧化二铝）上的吸附构型是吸附分子中的部分链节平躺在固体表面，部分链节以链环或链尾的形式伸向溶液，使吸附层具有一定厚度，形成空间阻碍作用。对于不同的腐蚀产物，聚 丙烯酸钠吸附的原因不同：在羟基氧化铁表面，是由于与表面上的re‘”形成络 合物：在三氧化二铝表面则是通过正负电性吸引。更多还原

【Abstract】 The mechanism of scale and corrosion inhibition of sodium polyacrylate (Na-PAAC) has been studied by electron spin resonance (ESR) technique, diffuse reflectance spectroscopy (DRS) FT-ER technique, chemical and electrochemical methods. Na-PAAC of low molecular weight was prepared by polymerizing acrylic acid in water using (NH4)2S208 as initiator and was spin-labelled by reacting with 4-mino-2,2-6,6-iperidinooxy. The ESR spectrum from the labelled polymer in aqueous solution consists of three distinct lines, the one to higher field being more broadened than the other two, reflecting the slower rotation of the nitroxide when attached to the polymer backbone as compared to free in solution. The adsorption of Na-PAAC onto scales from water was mainly induced by the attraction between positive charges on the scales and negative charges of polymer. The configuration of the adsorbed layer was that some segments of the adsorbed molecule were bound to the scale surface, some were dangling in the water. During the growing of scale crystal, the adsorption of the polymer at the active sites of crystal, which results in the repulsion between them, would inhibits the growing of the crystal effectively. Inhibition of Na-PAAC on carbon steel in hard water was investigated in the terms of potentiostatic steady-state polarization and A. C. impedance techniques. The results show that the ~ of the carbon steel did not moved but the transfer resistance (R~) was increased. The mechanism of inhibition was that the adsorption of Na-PAAC on the metal surface reduced the occurring area of corrosion reaction. The results of DRS FT-IR technique show that for different metal oxide, the reason of adsorption were different: on FeOOH, the Fe3~ ions on the surface in the presence of sodium polyacrylate formed a Fe( III )-PAAC complex; on A1203, the main induction was the attraction between positive-negative charges.更多还原