Selecting the Right Grade Makes a Difference
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Titanium dioxide (TiO2) is a key component of many coatings formulations due to its unique optical properties. Incorporated correctly, TiO2 can promote superior hiding, gloss and durability performance in paint films. However, efficiency of TiO2 performance in a coating is both a function of the inherent TiO2 physical properties and of proper grade selection and dispersion in the formula.
Titanium dioxide is obtained from ilmenite ores using either a sulfate or chloride production process. The sulfate process yields both anatase and rutile crystal forms of TiO2, while the chloride process yields only the rutile crystal structure. Rutile TiO2 is preferred for use in most coatings due to its higher refractive index (R.I.) and hence improved ability to scatter light in paint films. Figure 1 illustrates that light traveling through a film with a higher refractive index pigment will have a shorter overall path length (top illustration) when compared to a film with a lower refractive index pigment (bottom illustration). As long as the film thickness is greater than that indicated by the dotted line in the illustration, both films will appear white and opaque. However, if film thickness is reduced to the dotted line, light traveling through the film with the lower R.I. pigment will be partially absorbed by the substrate causing reduced hiding when compared to the film with the high R.I. pigment, which will remain white and opaque. Thus, choosing a high R.I. pigment such as rutile TiO2 (R.I. =2.73) to maximize the refractive index difference between the pigment and its medium allows for the greatest opacity development in the film. Additionally, TiO2 is unique among pigments in paint formulation because it provides both wet and dry hiding of the substrate by the paint film.
TiO2 particle size and distribution are controlled in the production process and influenced by pigment dispersion in the paint-making process. These properties affect final paint properties such as gloss, dispersion and hiding. Optimal light scattering occurs for well-dispersed TiO2 pigments at a particle size between 0.2-0.3 microns due to the combination of refraction and diffraction of visible wavelengths of light by pigments of this size. As shown in Figure 2, optimal optical properties for a paint film such as hiding power and tinting strength are achieved primarily by optimizing pigment particle size and distribution at less than 0.5 microns. Figure 2 also indicates that as particle size increases, film properties such as gloss and paint properties such as dispersion become negatively affected.
In addition to particle size and distribution, surface treatment is also controlled by the TiO2 production process. Pigment particles are surface treated with alumina, silica and organic coatings to promote dispersibility, hiding, and durability in paints (see Table 1). Grades such as DuPont(tm) Ti-Pure(r) R-902, R-706, and R-960 with moderate silica content are designed to promote photostability in coatings. Therefore, paints made with these grades generally display improved chalk resistance and gloss retention in outdoor applications. Surface coatings are also applied to pigments to act as physical spacers for the pigment particles in paint films leading to superior hide in paints formulated above critical pigment volume concentration (CPVC), as is the case with Ti-Pure R-931.
All major TiO2 producers offer a range of titanium dioxide pigments with excellent color and opacity performance. It is important to select the proper grade to achieve additional performance and appearance properties desired in coatings systems. Many key factors must be considered when selecting a grade for coatings applications (see Table 2).
While there is still a range of TiO2 products available, the list can be narrowed down quickly through the use of the checklist found in Table 2 in combination with the grade selection literature provided by titanium dioxide suppliers. When in doubt, consult your suppliers' website or the supplier's sales and technical service organizations.
For architectural or decorative coatings, there are two primary types of TiO2 pigments: those for enamel grade performance below CPVC and those with improved spacing characteristics for above CPVC paint applications. Ti-Pure R-706 and R-931 are available to cover this range of paints. R-931 offers effective hiding and cost efficiency for high-quality flat paints above CPVC if the customer is willing to stock multiple TiO2 products. A range of TiO2 dry and slurry grade choices exist for architectural coatings applications depending upon the need for exterior durability. Recommendations for various applications are listed in Table 3.
Ti-Pure R-706 and R-902 are recommended for use when a single pigment is required to perform well in both interior and exterior gloss and semigloss systems. R-706 is the ideal selection for applications requiring high gloss, maximum gloss retention, and chalk resistance. In addition, the small mean particle size and blue undertone of R-706 will provide brighter, cleaner colors in tinted systems. R-902 is slightly lower in hiding power, gloss, and dispersion than R-900, but higher in exterior durability. For paint manufacturers capable of handling TiO2 in aqueous slurry form, R-706 and R-902 are available in slurry forms-as R-746 and R-942, respectively, (see Table 1).
Ti-Pure R-902 is also highly chalk-resistant; it performs well over a range of solventborne and aqueous systems where tint retention is important. R-900 has medium chalk resistance and is preferred when dirt collection is a problem. These pigments can be used in both alkyd and emulsion paints (see Table 1).
Tinted house paints, including both white and tinted trim paints, require a high degree of chalk resistance and gloss retention. Ti-Pure R-706 is recommended for emulsion trim paints because it provides maximum initial gloss and outstanding exterior durability. These last two properties result from lower PVC and generally better binder durability associated with exterior emulsion trim paints. R-902 also satisfies these requirements over a range of solventborne and aqueous systems.
Ti-Pure R-931/R-941 performs well in selected exterior white latex house paints, following reformulation to accommodate the higher surface area of the pigment and to maintain film integrity. When exterior durability is desired in a flat paint, R-902 is also highly recommended.
In most high-performance coatings requiring exterior durability with excellent color and gloss retention, there are few TiO2s that hit this mark. Most suppliers offer one or two pigment types in this area, such as R-960 for the most demanding exterior durability (gloss and color retention) applications, and R-706, which meets many stringent requirements and can often provide improved initial gloss in combination with the desired gloss and color retention.
For general industrial applications, R-902 multipurpose pigment has been an industry standard for over 35 years. In addition, R-900, R-960, and the modern grades R-700 and R-706 are suitable for many OEM and special-purpose paint applications as well. R-706 and R-960 remain a preferred combination for powder coatings applications. Today, the universal type pigments such as R-706 are being used in a range of general industrial OEM and special-purpose applications where both performance and aesthetics are desired. The universal pigments offer high tint strength, crisp bluer undertones, lower dispersant demand, easy dispersion, high initial gloss, and excellent gloss and color retention. A more detailed discussion of TiO2 grade application by subsegment follows.
Topcoats: Ti-Pure R-706 combines high gloss and distinctness of image with excellent resistance to weathering for high-quality OEM and refinish topcoats. However, R-960 is the most durable Ti-Pure pigment available, making it also ideal for OEM and refinish applications. R-902 is less resistant to weathering than R-960 or R-706 but provides an excellent balance of properties.
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Ti-Pure R-706 is the most widely applicable grade, possessing a combination of exceptionally high gloss and excellent exterior durability unique in the industry. It can be used in both interior and exterior coatings where this combination of gloss and durability combined with excellent dispersibility is of value. R-960, although lower in gloss than R-706, provides outstanding chalk resistance and tint retention and should be used in premium-quality exterior finishes where resistance to chalking and color change are of primary importance. Applications include coil coatings for residential aluminum siding and architectural building panels, aerospace coatings, and other high-durability applications. Because of their silica surface treatment, both of these grades provide better film cure in acid-catalyzed coatings than nonsilica-treated grades.
Ti-Pure R-902 is used in high-quality finishes that require very good chalk resistance and gloss retention, but not the exceptional performance provided by R-706 and R-960. This grade is often used in industrial maintenance, implement and transportation finishes, and some container coatings.
Ti-Pure R-700 and R-900 are both used primarily for interior coating applications. R-700 is recommended for most applications and provides the highest gloss combined with a blue undertone for clean tints. Compared with R-900, R-700 provides better film cure in acid-catalyzed coatings because of its neutral pH and lower level of alumina surface treatment. R-900 is widely used for can coatings where its neutral undertone and high gloss are valued. Applications for both grades include appliance coatings, metal furniture finishes, and high-reflectance white coil coatings.
OEM and Special-Purpose Coatings. While it is possible to use a single universal pigment such as R-706 over a range of industrial applications, typically most coatings producers still use at least two or three pigments. One TiO2 grade typically is a multipurpose grade such as R-902, another would be a universal pigment such as R-706 for high gloss, and third an R-960 type for the most demanding exterior gloss and color retention applications. Because most industrial producers participate in a range of market end-uses, a single TiO2 grade is a more challenging goal as compared to decorative coatings applications.
First, consider the initial wet-in of the pigment in an appropriate solvent system. Wetting of the pigment occurs when air or other substances are displaced from the pigment surface by solvents and/or wetting agents such as surfactants or dispersants. The wetting rate is influenced by the surface treatment on the pigment and by wetting agents included in the formulation. Following wet-in, shear must be applied in a grinding step to break up pigment aggregates and agglomerates. The level of shear stress must be determined for each pigment grade to yield a reasonable evaluation of the ease of dispersion for that grade in a defined system. The shear stress applied to the system differs markedly depending on the type of equipment involved and must be evaluated independently for high-speed dispersers, sand grinders, roller mills, and pebble mills. The success of the dispersion and grinding process is reflected in the gloss and tint strength of the final paint and in the dispersion measurements made on the paint grind. As a final consideration, well-dispersed TiO2 particles must be stabilized within the paint system by either charge or steric stabilization.
Flocculation, or loose clumping of TiO2 particles, may occur as the result of poor dispersion or mismatched surface interactions of the pigment with other components in the paint formulation brought on by temperature, pH, or improper type or concentration of dispersant. Flocculation should be avoided as it may lead to issues with viscosity, color acceptance, grind consistency, gloss and hiding in the paint film.
Ti-Pure(r) is a registered trademark of DuPont for its brand of titanium dioxide.
For more information on titanium dioxide, contact Stephen J. Hurff, Ti-Pure Product Manager, Coatings, DuPont Titanium Technologies, Chestnut Run Plaza, Building 709, Wilmington, DE -; ; 302/999.; fax 302/999.; or Circle Number 121.
This article is an attempt to let you know about the use of titanium dioxide (TiO2) in paints, coating. A metal of great strength, titanium. A combination of its strength, heat resistance, water and salt resistance, and lightweight makes it an ideal metal for a number of applications. When it comes to pure titanium it can be considered strong and corrosive while gaining greater flexibility and malleability when mixed with another metal.
There are six grades of pure titanium (grades 1,2,3,4,7 and 11) and 4 varieties of titanium alloys. In addition to titanium, titanium alloys generally contain aluminium, molybdenum, vanadium, niobium, tantalum, zirconium, manganese, iron, chromium, cobalt, nickel, and copper.
Sage Oil LLC is a leading titanium dioxide manufacturers in production capacity, product quality, and customer service. As a worldwide titanium dioxide supplier, Sage Oil LLC is committed to providing excellent quality to our clients.
Titanium dioxide (TiO2) is widely used in the coatings industry as a white pigment. Because it effectively scatters visible light, both whiteness and brightness are imparted to a coating when it is incorporated.
Anatase and rutile are the two crystal structures of titanium dioxide available for commercial use. The main reasons for preferring Rutile TiO2 pigments over anatase pigments are that these pigments scatter light more effectively, are more stable and have a longer shelf life.
We all know that exposure to sunlight can dull the color of clothes, outdoor paints and whatnot. TiO2&#;s refractive properties, durability and brilliance of color is the main reason to be used in outdoors plastic as it gives them a rigid strength to avoid any kind of weathering and light damage due to its refractive property. When entering or leaving a material, the amount of change in the path of light depends on the refractive index, which is determined by the electronic structure of the molecules.
It can be tricky to study the weather resistance of a coating. An outdoor exposure test over a period of several years is the most effective way to determine the weather resistance of a coating system. It is necessary, however, to evaluate the weather resistance of a paint system in much shorter time frames during the development process.
Three main factors of degradation of outer coating are
Titanium dioxide helps in creating an opaque film over the outer surface which would lead to dispersion of light. This makes the outer surface last longer.
Titanium dioxide is a white substance generally in a fine powdered form that is insoluble in water. An acidic environment is the most common means of using hydrogen peroxide. Solubilizing titanium oxide in water is performed by hydrogen peroxide.
In large quantities, titanium dioxide negatively affects both the hiding power and the adhesion of paint. If the PVC content is above 30% in TiO2, the white color strength will increase.
To ensure that a system containing titanium dioxide pigment is able to provide whiteness and hiding power due to scattering, particle-free PVC must not exceed a threshold value of 30% by volume. As long as PVC in TiO2 is below 30%, the total PVC, taking all solid particles into account, of a system can be (much) higher than 30%.
Yes, Titanium dioxide can be used in paints, coatings, plastics.
As well as being odourless, titanium dioxide is absorbent. When powdered, this pigment serves as an opacifier and a source of whiteness.
Yes, in most of the paint or titanium dioxide is found.
Between 5 to 10 years.
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