THE USE OF PHOTO-CONDUCTIVE AND MICROWAVE TECHNIQUES FOR THE EVALUATION OF TITANIUM-DIOXIDE PIGMENT ACTIVITY IN POLYMERIC SYSTEMS

The feasibility of measuring the photo-activity of titanium dioxide pigment particles has been evaluated using two non-contact methods; namely photoconduction and dielectric properties. The initial measurements of the photo-response of pigment particles in the binders suggested that it was possible to distinguish between the pigment types used. It was found that there were differences between the two crystalline forms of the pigment, and between the coated and uncoated pigments, as well as between the different commercial grades of pigments. With the dielectric measurements, it was found that there were diversities between the different types of pigments used. The Carbonyl Index was used as a comparable reference on the photoactivity of the pigments in the binder studied, such that the results from the two techniques may be correlated. From these initial measurements, it was encouraging to observe that there were some similarities between the results from the two techniques. The implications of both methodologies are discussed with a view to establishing a rapid method of assessing pigment durability.