How to whiten the paint?
The whiteness of white paint mainly depends on the whiteness and hue of the titanium dioxide or other white color or filler used. The reflectivity of titanium dioxide to incident light is not 100%, especially for wavelengths in the blue and violet bands, the absorption rate of titanium dioxide is still quite high, which causes it to be not pure white, but with a yellowish hue. We can change the color phase by adding a small amount of additives, the principle is to increase the system blue color light, in order to mix with the yellow color light to get white, improve the whiteness of the paint. Specifically, there are several common methods of paint whitening as follows.
First, add fluorescent whitening agent.
Fluorescent whitening agent can absorb ultraviolet light with a wavelength of 300~400nm, and this function is quite similar to UV absorber. But the UV absorber is the absorbed energy into heat release, while fluorescent whitening agent is to absorb ultraviolet light and shoot blue-violet fluorescence, fluorescence of the main wavelength of 420 ~ 480mm, so it can significantly improve whiteness and “gloss. *A white object is one that reflects 100% of the incident light, and the addition of fluorescent brighteners can make people feel whiter visually. Blue tones appear whiter than white with yellow tones, so increasing the saturation of blue can achieve the visual effect of increasing whiteness.
Second, the use of very high whiteness of titanium dioxide.
Choose very high whiteness titanium dioxide, can improve whiteness, other raw materials also try to use water clear color, in sufficient amount of very white titanium dioxide, the whiteness of the paint is very high. Rutile titanium dioxide although the color phase is yellow, but good coverage, high whiteness. Anatase titanium dioxide color phase is not yellowish, poor hiding power, whiteness is not high, cold tone, but some people think it is “very white”, which is a different hobby.
Third, hanging blue.
Due to the use of rutile titanium dioxide color phase yellow, then it can be used to complement the purple pigment, such as ultramarine can eliminate the yellow, so that the paint appears more white, commonly known as hanging blue. Ultramarine is *ancient and *vivid inorganic blue pigment, non-toxic and environmentally friendly. Ultramarine is a brightly colored blue-violet powder, which can eliminate the yellow color light within the white substance and produce blue light whitening effect. Ultramarine is alkali-resistant, heat-resistant, light-resistant, weather-resistant, insoluble in water, and decomposes and fades when it meets acid. Ultramarine is made from a mixture of sulfur, clay, quartz, and charcoal, and is fired.
In the case of complex color can also additionally add purple pigment or blue-violet phase of phthalocyanine blue to hang blue to be more white.
Fourth, high pigment volume concentration (PVC) paint.
In fact, the white pigment is not titanium dioxide or zinc oxide, but “empty”, that is, “air bubble”, look at the whiteness of the soap bubble and foam will know. Therefore, when the PVC of the paint crosses its CPVC, it introduces the *white pigment – “air bubble” in the dry film of the paint, and the whiteness of the paint increases significantly at this time. This is how many of the “super white paints” for construction that are popular in the market** are designed. When designing a very white paint, the defects of the raw materials introduced must be taken into account and disposed of appropriately. For example, the weathering resistance of anatase titanium dioxide and whitening agent is poor, the acid resistance of ultramarine is poor, and the strength of air bubbles is reduced.