What Factors Affect the Coating Gloss ?
1. Significance of measuring the gloss of the coating
From a physical point of view, gloss is considered to be the ability of the paint film surface to reflect the light projected onto it to a mirror surface. The greater the amount of reflected light, the higher the gloss. This is called specular gloss. Reflected light in the specular reflection direction is called specular reflection light, while non-specular reflection light is called diffuse reflection light. For ordinary engineering applications, the coating gloss is generally maintained at a moderate level. The coating is changed by simple physical and chemical methods. The surface state of the layer can achieve the required gloss; but for some special needs, when the coating has a high or low gloss, it is difficult to achieve it by changing the surface state of the coating. Consider changing the gloss of the coating. This paper studies the principle of coating gloss measurement, uses optical theory to give an approximate expression of coating gloss, analyzes the main influencing factors of coating gloss. Then theoretically calculates the relevant characteristics of coatings on coating gloss at high and low gloss.
2. Composition of coating surface gloss reflection
Since the emitted energy and the receiving cross section are constant, the gloss is mainly affected by the surface reflection characteristics of the coating. The surface gloss reflection of the coating is mainly composed of 2 parts, one is fresnel reflection. The other is related parameters and structure of the material inside the coating. The apparent reflectance of the coating is determined by the fresnel reflection and the coating. The substrate reflection, fresnel reflection and coating absorption coefficient and scattering coefficient are related.
For general glossy coatings, you can change the surface state of larger glossy coatings and adjust the micro-roughness of the coating surface, thereby changing the light scattering characteristics of the coating, reducing the specular reflection of the coating. The coating gloss can usually be reduced by matting the coating.
3. Methods to reduce gloss
In combination with the mechanism of the coating film surface gloss and the factors that affect the gloss, extinction is to use various methods to destroy the smoothness of the coating film, increase the surface roughness of the coating film. Then reduce the reflection of light on the coating film surface. It can be divided into physical extinction and chemical extinction. The principle of physical extinction is: adding a matting agent to make the coating surface uneven during the film formation process, increasing the scattering of light and reducing the reflection. Chemical matting is to obtain low gloss by introducing structures or groups that can absorb light. However, when the gloss required by the target coating is very high or low, it is difficult to effectively change the gloss of the coating by changing the surface state. At this time, the high-gloss or low-gloss coating can be obtained by changing the physical characteristics of the coating. .
It can be seen from the above that when the incident angle is constant, the fresnel reflectance of the coating does not change significantly with the refractive index of the coating. The refractive index of different coatings does not change significantly, so different color coatings can reflect better gloss. When the coating gloss is very high, changing the surface state can no longer effectively change the coating gloss. The coating gloss can be changed by changing the refractive index of the pigment in the coating. Take 20 ° gloss as an example. When the refractive index increases from 1.7 to 2.2 GU, its fresnel reflectance doubles, which can effectively increase the gloss of the coating.
4. Material gloss is measured with a gloss meter
Whether high gloss or low gloss. Its gloss value must be within a certain reasonable range. At this time we need to use a gloss meter to detect the gloss of the material surface. Linshang gloss meter is very convenient for measuring the gloss of materials. The gloss of the material can be measured in real time. After pass the self-calibration, the measured gloss will be immediately displayed on the interface. And it is very convenient to record and save the current data by pressing the button.