Surface modification of kaolin. 2. Enhanced steric stabilisation of polymer-modified kaolin

The polymer-modified surface of kaolin was studied to determine the effect of changing the molecular weight of the polymer chain grafted on the surface. The particle was modified by attaching poly(ethylene oxide) to the surface using a urethane linkage. Upper critical flocculation temperature and contact angle measurements were conducted to quantify the changes in surface characteristics and stability in an aqueous dispersion. The effect of pH on stability and grafted density of polymer chains showed the mechanism of stabilisation to be that of enhanced steric stabilisation. The kaolin particle was also modified with the more hydrophobic poly(propylene oxide). The behaviour was characterised as for poly(ethylene oxide) and interesting differences in extent and mechanism for stabilisation were observed.