The Coverage Of Titanium Dioxide
Coverage power refers to the ability of the pigment in the paint to cover the background color of the surface of the coated object when an object is coated with a certain paint, so that the background color can no longer be revealed through the paint.
The most important role of titanium dioxide in the industry is to use its opaque properties to be dispersed into the medium, so as to achieve masking effect.
1.Refractive index of titanium dioxide
1) The refractive index of the crystal itself.
The refractive index of titanium dioxide is the highest among white pigments, so theoretically its refractive index is also the highest.
2) The size of the pigment particle size and the degree of dispersion of the particle structure also affect the hiding power.
In the range greater than the half-wave wavelength of visible light, the finer the particle size, the smoother the particle structure and the better the dispersibility, the greater the covering power, but it has a certain limit. When the average particle size is um, the hiding power is the largest. When the wavelength is less than half of the wavelength of visible light, the covering power decreases due to the transparency of the crystal grains to light. Because the visible particles are too large or too small, it is not good.
The hiding power of a pigment depends not only on its crystal structure, refractive index, and light-scattering ability, but also on its light-absorbing ability. But titanium dioxide is the same as other white pigments, because its light absorption ability is very small, although the light absorption has an impact on the covering power, it does not have a large influence on the scattering ability, so its covering power is mainly affected by the scattering ability. The same tinting strength It is also affected by the refractive index, particle size, particle size distribution and dispersion properties of the pigment.
2.The factors affecting the coverage of titanium dioxide are as follows:
1)The refractive index of titanium dioxide crystal itself. The coverage of titanium dioxide is the highest among white pigments, so theoretically, its hiding power is also the highest.
2)The particle size, particle structure and dispersion degree of titanium dioxide also affect its covering power.
The hiding power is also directly related to the particle size of titanium dioxide. Generally speaking, in the coating system with high pigment volume concentration, the hiding power of titanium dioxide pigment with larger particle size is higher; in the coating system with low pigment volume concentration, the particle size Smaller titanium dioxide pigments have higher hiding power.
From an optical point of view, the reflection and absorption of light by pigments can cause covering and achromatic effects. In the full range of visible light, white pigments can almost reflect all wavelengths of visible light with equal intensity, so the scattering energy is large and the absorption energy is very small. . Therefore, the main direction of improving opacity, covering power and achromatic power is to improve the scattering ability of titanium dioxide, followed by reducing the absorption ability of titanium dioxide.
The main means to improve the scattering ability of titanium dioxide is to make the particle size and particle size distribution of titanium dioxide meet the requirements of varieties and have good dispersibility. Reducing the absorption capacity mainly depends on removing impurities that can produce color as much as possible during processing, and improving the purity of titanium dioxide to reduce light absorption energy.
3.Detecting coverage of titanium dioxide method:
- Pinch with your hand to see the covering power of the white cover. Compare the effect with the real product. 2. Add acid and test to see that the foamer is mixed with light calcium and heavy calcium.
- The smell of the gas is lithopone.
- Those mixed with talc powder will feel slippery when kneaded. Put it in the water and float on the water surface. 5. Measure the specific gravity.
- The most difficult to measure is the exchange of anatase and rutile titanium dioxide. The appearance and color are the same. Only by borrowing the instrument. Or when the ultraviolet light is baked and turns yellow, it is anatase.
In general, architectural coatings manufacturers should perform the following routine performance tests on purchased emulsions.
1）Appearance—General visual inspection. Observe the shade of the lotion and the presence or absence of particles and impurities.
2） Viscosity. Since most polymer emulsions are non-Newtonian fluids, the instrument used to measure emulsion viscosity should be able to measure shear stress versus shear rate over a wide range of shear rates. Rotational viscometers are usually used to measure the viscosity of emulsions, generally not 4 cups.
3）Determination of solid content, put about 2 g of the polymer emulsion sample into an aluminum pan (or glass pan) with a diameter of 4 cm, cover it with an aluminum cover (or glass cover) and weigh, and place its solid content to pass through the ventilation device. Dry in an oven at 115 °C for 20 min and weigh to calculate. For easily peelable polymers such as acrylates, the above method should use a higher drying temperature (eg 120°C). For plasticized polymer emulsions, lower temperature (eg 105°C) and longer drying time (eg 2h) should be used due to the volatility of the plasticizer.
4) pH value, measured with precision test paper or appropriate type of pH value measuring instrument.
Jinan Hongquan Titanium Industry Co., Ltd.( Greatspring) is located in Jinan, a beautiful spring city. The company’s scientific research personnel sincerely cooperate with well-known domestic universities and various titanium dioxide production enterprises to study and produce active titanium dioxide pigments with great concentration. Some of its products have been widely used in chemical, textile, paper, plastic, paint and other production fields.
The company’s products (likeDongfang、Lomon Brand Lomon titanium dioxide) have been demonstrated by well-known national experts, and the conclusion is: “technological innovation is strong, improves the performance and utilization of pigments, reduces dosage, saves resources, economic benefits, no environmental pollution, in line with national industrial promotion and development strategies”