April 11, 2025 – In the realm of chemical pigments, rutile titanium dioxide stands out as a star product. As one of the two key types of titanium dioxide, it occupies an indispensable position in numerous industries thanks to its remarkable properties.
Rutile titanium dioxide is an extremely high – quality white pigment, boasting high dispersibility, excellent weather resistance, high hiding power, and remarkable stability. It is widely used in a variety of fields, ranging from interior and exterior wall latex paints to industrial coatings, from composite inks and flexographic inks to laminated papers, plastic color masterbatches, and powder coatings. So, what unique physical properties does this much – favored rutile titanium dioxide possess?
Regarding relative density, the relative density of titanium dioxide is influenced by factors such as crystal form, particle size, chemical composition, especially the amount of surface treatment. During the manufacturing process, as the calcination temperature rises and the time prolongs, its relative density increases. Among common white pigments, titanium dioxide has the lowest relative density. This means that for the same mass, it has the largest surface area and the highest pigment volume. Specifically, the relative density of anatase titanium dioxide ranges from 3.8 to 3.9 g/cm³, while that of rutile titanium dioxide is 4.2 – 4.3 g/cm³.
In terms of melting and boiling points, anatase and brookite titanium dioxide transform into rutile type at high temperatures, so they do not strictly have melting and boiling points. There are different views on the melting point of rutile titanium dioxide. Generally, it is considered to be between 1800 – 1875℃. Some data indicate that the melting point in air is 1830 ± 15℃, and in an oxygen – rich environment, it is 1879 ± 15℃. Moreover, the melting point is related to purity. Its boiling point is (3200 ± 300)K.
According to AsiaMB, the dielectric constant is an important indicator reflecting the electrical properties of rutile titanium dioxide. Due to its high dielectric constant, under an external electric field, the interaction of ions forms a strong local internal electric field, causing the outer – layer electron orbits of ions to deform and the ions to displace. The dielectric constant of rutile titanium dioxide varies depending on the crystal direction. It is 180 parallel to the C – axis, 90 at a right angle, and the average value for powder is 114, which is much higher than 48 of anatase type.
Rutile titanium dioxide also has semiconductor properties. Its electrical conductivity increases rapidly with the rise of temperature and is sensitive to oxygen deficiency. For example, at 20℃, it is an insulator, and at 420℃, its electrical conductivity increases by 10⁷ times. The electrical conductivity of stoichiometric TiO₂ is <10⁻¹⁰ s/m, while that of TiO₁.₉₉₉₅ can reach 10⁻¹ s/m. This property is widely used in the production of components such as ceramic capacitors in the electronics industry.
In terms of hardness, on a 10 – point Mohs hardness scale, the hardness of anatase titanium dioxide is 5.5 – 6.0, and that of rutile type is 6 – 7. Hardness is related to crystal structure, product purity, and calcination temperature. High – temperature sintering will increase the hardness. Due to its high hardness, it causes significant wear to spinnerets and rollers, so it is not suitable for chemical fiber delustering and gravure printing.
Regarding hygroscopicity, titanium dioxide is hydrophilic but not highly hygroscopic, and anatase type is slightly more hygroscopic than rutile type. Its hygroscopicity is affected by the nature of the surface treatment agent and the specific surface area. Materials with a larger specific surface area have slightly higher hygroscopicity.
In addition, titanium dioxide is a thermally stable compound. When strongly heated in a vacuum, it will slightly lose oxygen and turn dark blue, but this reaction is reversible, and it will return to white after cooling. The rich and unique physical properties of rutile titanium dioxide enable it to continuously play an important role in the chemical industry and related industries.