STUDY ON THE DISPERSING EFFECT OF POLYCARBOXYLATE-BASED DISPERSANT

摘要

Polycarboxylate -based air-entraininghigh-range water-reducing agents contain apolycarboxplate-based dispersing agent (PA) and adispersion retention agent. The PA adsorbs to thesurface of the binding material particles. Due tosteric effects, the particles are highly dispersed,resulting in a high level water reduction and highfluidity 1,2). It is considered that in the study of thedispersion effects of air-entraining high-range water-reducing agents, it is important to understand theadsorption properties of the PA. We focused on themolecular size and adsorbed number of PAmolecules. Based on the chemical structure andmolecular weight of the PA, we calculated itsmolecular size and determined that the maximumlength of the extended main chain is 20 nm and thatof the side chain was 7 nm. Considering the effectivevolume based on thermodynamics, one PA moleculeis adsorbed to every 400nm~2 of particle surface.However, according to calculations based on theactual measurement of specific surface area andadsorption 'mounts, one PA molecule is adsorbed toevery l00nm~2 of the particle surface. It is suggestedthat PA molecules shrunk and adsorbed on to thesurface of binding materials, more than imagination densely.