水性体系pH值对炭黑分散的影响

The Effect of pH Value Variation on the Dispersion of Carbon Black in Waterborne System

本文在测定了三种不同炭黑的表面酸碱性的基础上,分别考察了分散剂结构、炭黑的表面性质对炭黑粒子与分散剂之间锚接强度的影响以及pH值对炭黑粒子间电斥力的影响。研究发现以离子型聚合物分散剂分散炭黑时,粒子间主要靠分散剂吸附层产生的位阻斥力达到分散稳定;而以非离子表面活性剂为分散剂时,由炭黑粒子表面酸性官能团解离所产生的电斥力对分散体系中粒子的分散稳定起着重要的作用。水性分散体系中,体系pH值的增加有利于炭黑表面酸性官能团和分散剂盐基亲水端的解离,从而增加粒子间的电斥力,提高炭黑的研磨效率和分散稳定性。

Based on the determination of surface acidity of three forms of carbon black, the effect of the structures of the dispersants and the surface property of carbon black on the interaction between them, together with the effect of pH value on electrical repulsion between carbon black particles in waterborne system has been investigated. At the same time, these carbon black particles if being dispersed with three different dispersants, viz., ionic polymer, amphoteric polymer and nonionic surfactant in various systems, the knowledge about the influence of pH value on the dispersion of carbon black could be acquired . It was found that carbon black particles would be stabilized mainly by steric hindrance caused by the adsorption layer of the dispersant on the surface of carbon black particles, if dispersed with ionic polymer, but these particles would be mainly stabilized by electrical repulsion due to the ionization of the acidic group on carbon black while being dispersed with nonionic surfactant. Therefore, it is beneficial for the preparation of a stable slurry with good dispersivity, a dispersant chosen should be of a planar structure bearing a hydrophobic group, so an π - π interaction with carbon black particles would be resulted. In waterborne system, the increment of pH value is beneficial for the improvement of electrical repulsion between particles, thus promoting the dispersivity and stability of carbon black particles.