Influence of non-ionic polymers on the rheological behaviour of Na+-montmorillonite clay suspensions. Part II. Homopolymer ethyleneoxide and polypropylene oxide–polyethylene oxide ABA copolymers

The rheological behaviour of Na+-montmorillonite suspensions in the presence of non-ionic polymers has been systematically investigated. Two different series of non-ionic polymers were studied. The first consisted of ABA block copolymers of polyethylene oxide–polypropylene oxide–polyethylene oxide (PEO–PPO–PEO or PE series), of varying ethylene oxide chain length. The second was a linear polyethylene oxide polymer of different molecular weights (PEO series). Thus the role of the polymer structure and ethylene oxide chain length on the rheological behaviour of the clay suspensions was addressed. Adsorption measurements were made with the purpose of quantifying the amount of polymer adsorbed on the Na+-montmorillonite surface. Rheological properties of concentrated clay suspensions (3–6% w/w) were determined as the polymers gradually covered the clay particles. Flow curves were obtained from shear stress–shear rate measurements, and were fitted to the Herschel–Bulkley model. The viscoelastic properties of the suspensions were determined from dynamic oscillatory measurements. These results demonstrate that adsorption of non-ionic polymers on the Na+-montmorillonite particles led to a gradual stabilisation of the suspension. The stability was enhanced for a longer ethylene oxide chain length and was found to depend on polymer structure.