Surface modification of Quinacridone Red (QR) pigment was carried out using a low temperature NH3-plasma. The dispersion behavior of such treated QR pigments was studied in three water soluble acrylic resins which had different hydrophilicities. The longer the NH3-plasma treating time was, the more the hydrophilicity (the heat of immersion in water) was given to the QR surface. As the heat of immersion (HI) increased, the gloss of QR-dispersed paste increased at first, reached a maximum when the HI was about 0.25J/m2, and then decreased. On the other hand, as the HI increased, the yield value of the pigment-dispersed paste decreased at first, reached a minimum when the HI was about 0.25J/m2, and then gradually increased. The same tendencies were observed within this experiment, though the resins were different in hydrophilicity. However, the higher gloss and the lower yield value of QR-dispersed paste were obtained by using the resin of the lower hydrophilicity. From these results, the existence of the optimum hydrophilicity value of pigment surface, that had been expected in our previous study, was experimentally confirmed.
Fine powder of TiO2 was treated with various chlorofluoromethanes or CHF3 in an ordinary flow reactor under an atomospheric pressure for the surface modification of the powder. The results revealed that surface fluorination readily proceeded at temperatures higher than 250°C, especially at above 350°C. Chlorine component was little introduced into the surface except for the treatment using CCl3F. The effect of the treatment on the surface acidity was highly dependent on the pretreatment temperature. Thus, the surface acidity of TiO2 heat-treated at 600°C was fairly enhanced by the chlorofluoromethane-treatment ; on the other hand, that of TiO2 heat-treated at a much higher temperature, 900°C, was decreased by the treatment because surface fluorination took place instead. Adsorptions of hexane and water vapor showed that the treated TiO2 surfaces turned out to be more hydro- and lipo-phobic with the treatment. In addition, a test for the photo-catalytic activity of TiO2, displayed that the TiO2 surface was made to be more stable to UV light by the chlorofluoromethane-treatment.
Adhesion of organic coatings on steel on exposure to water (wet adhesion) is the most important property for a good corrosion protection, The glass transition temperature (Tg) of the coatings is a factor determining the wet adhesion. Tg of many coatings is lowered by water. This work investigates how the water uptake affects the Tg of various coatings. A coating-stressmeter was used to determin Tg in dry and wet conditions. It was found that water disrupted the intermolecular interactive hydrogen-bridges and hence reduced the Tg of an exposy-polyamine greatly. A good wet adhesion is expected if the interaction between coating and steel surface is stable to effects caused by penetrating water. Increase in Tg by dispersing iron oxide flake treated by poly (acrylic acid) solution indicates how to achieve the stable interface for a good corrosion protection.