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Preparation and characterization of sterically and electrostatically stabilized TiO2 suspensions
The aim of this study was the investigation of stable Ti02 powder suspenSIO formation in water. The water based paints are environmentally safe and expected to replace organic based solvents.Four different commercial titania pigment powders with different characteristics were used. Only a high molecular weight surfactant was used. Suspensions were prepared for four titania powders at 5,1O,and 20 % by volume solid content and the same suspensions were used in the investigation of the effects of the surfactant on the stability of suspensions. The surfactant was added in the range of 0.1 to 0.5 % by weight of pigment.Two characterization methods were used III the analysis: sedimentation and rheological characterization.It has been found that there are some stable pH ranges for the suspensions prepared by four Ti02 powders. In these ranges, it is expected to behave as dilatant - shear thickening and the sediment was densely packed. Three zones, sediment, falling and supernatant zones, were observed in disperse suspensions ..As a result of this, the pH ranges of these powders in water is observed visually. If it has rutile structure in powder C G (95% Ti02 content, 5% Ab03 coated), it works very well in basic mediums. Also rutile powder G (99% Ti02 content, uncoated), it is expected at pH.2 and basic mediums. The anatase powders ,E and F (both are 99% Ti02 content, uncoated), are stable in basic mediums. The F has wider stable zone than the powder E.The results of this work have shown that rutile alumina coated powder C suspensions were stable in basic media. Rutile powder G suspensions were stable at pH.2 and basic media. Anatase powders E and F were stable in basic media with powder F being stable in a wider pH range. The combined analysis of sedimentation -rheological behaviour of suspensions were found to be very helpful in understanding the suspension behaviours. Relatively high sediment packing densities in the 50-60% of theoretical titania density were obtained for some of the suspensions.