Functional verification of the hottest wet sericit

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Function verification of wet sericite in coating

adding wet ultrafine sericite powder to the coating can shield ultraviolet radiation, improve the weather resistance of the coating, and delay pulverization and discoloration; The two-dimensional sheet structure with high aspect ratio enhances the comprehensive mechanical properties of the coating, waterproof, impermeable, crack resistant, and enhanced pollution resistance and self-cleaning; Acid, alkali and high temperature resistance, improve the heat resistance and corrosion resistance of the coating

I. mechanism of wet sericite powder application in coatings

(I: wet sericite has unique UV shielding characteristics

(1) polarization effect of crystal

H.S. Katz and others in the United States believe that the extinction performance of inorganic fillers depends on the different orientation of mineral crystals and their ability to absorb or reflect UV rays. Sericite mineral structure belongs to monoclinic system, with three crystallization axes a, B and C (see Figure 2). The included angle between a axis and C axis is 93 °, and b axis is perpendicular to a axis and C axis. Sericite has three main refractive indexes: ng=1 615,Nm=1.. 611,Np=1.. 572, optical orientation: ng is parallel to the b axis, there is an included angle of 3 ° between nm and the a axis, and NP is parallel to the c axis. The optical volume diagram (center of Figure 1): it is composed of three elliptical sections: ng NP plane (vertical), NM ng (horizontal), NM NP (longitudinal). The ng NP elliptical section has two optical axes, called the optical axis plane (ng NP), with NP (c axis) as the bisector, and the included angle 2v= ° the optical axis angle of Muscovite is °. The degree of extinction of inorganic minerals is related to the optical axis angle. The larger the optical axis angle is, the lighter the grayness is, and the higher the interference color is; The smaller the optical axis angle is, the higher the grayness is, and the better the extinction effect is. Therefore, sericite minerals are better than Muscovite in shielding ultraviolet rays and microwave, which is superior to other inorganic fillers

in addition, the shading effect is related to the arrangement order of minerals. Granular and fibrous minerals are arranged disorderly and oriented randomly in the film. The flake sericite has a high Baumert in the film. "One of the innovative ways is to transfer the products that have been mature in one field to other fields. It is generally arranged in parallel and overlapped up and down. When the optical axis planes (ng NP) of the upper and lower flakes are perpendicular to each other, it will produce full extinction, and when they are oblique, it will produce interference color.

(2) Interference effect of interlayer water molecules

sericite crystal contains crystal water, which is 2% higher than muscovite. The refractive index of crystal water is 1.33 and that of aluminosilicate is 1 615, there is a large difference between the two, and the refractive effect is strong. The spacing between the middle layers of Sericite structure is about 10, which is close to the wavelength of ultraviolet and microwave. When the natural light passes through sericite crystal, due to the polarization vibration of the crystal, the light is decomposed into two polarized beams of ng and NP with different light velocities, which are decomposed again when passing through the layer, resulting in ng 'NP' phase overlapping on a polarization plane. When the polarized light energy is gradually attenuated to zero, it is completely shielded and there is extinction

(3) UV absorption performance test of Sericite

high performance coatings hope that raw materials can provide excellent weather resistance. It is generally believed that the weather resistance of fillers depends on UV absorption energy. The stronger the ability to absorb UV, the greater the contribution to the weather resistance of the film. Now, the ultraviolet absorption spectra of titanium dioxide and our company's wet sericite, kaolin and other fillers are shown in Figure 2

Figure 2: Determination diagram of absorbance of pigments and fillers such as titanium dioxide and sericite


1. Detection instrument: lambda 900 UV is/nir spectrometer

2. The wavelength of ultraviolet light is: nm

the chart shows that rutile titanium dioxide has an absorption trough of 88%, greaved wet sericite has an absorption trough of 85%, dry sericite has an absorption trough of 48%, calcined kaolin has an absorption trough of 59%, and other mineral fillers basically have no absorption function of UV

longer light wave energy can only make molecules vibrate and the rotating surface generate heat. Ultraviolet can destroy the chemical bonds of C-H, C-C, C-Cl and other substances with the same bond energy in organic substances, thus causing the degradation of organic substances and polymer compounds into small molecules. Ultraviolet radiation will destroy and decompose the molecular structure of pigments in the paint, degrade into other substances, and make the paint fade or change color. The use of wet sericite powder protects the C-H bond in polymer materials, so it has the properties of anti discoloration and delayed pulverization

II: sheet barrier function of wet sericite

the effect of inorganic minerals on film strength and water resistance in coatings is related to the physical shape of minerals, which generally decreases in the following order: Sheet> fibrous> columnar> granular. The crystal of Sericite has a two-dimensional sheet structure, and it is sheet no matter how ultra-fine it is. In addition, sericite has active hydroxyl groups, which are easy to combine and entangle with the molecular chains in emulsion and solvent. It is arranged in parallel and overlapped up and down in the film, so that a dense layered structure is formed inside the film, which greatly improves the comprehensive mechanical properties and permeability resistance of the film

Figure 3: electron microscope photo of wet sericite

Figure 4: the penetration path of water in different structural coatings

II: functional verification of wet sericite in coatings

wet sericite is widely used in the following coating fields with its unique physical and chemical properties and application functions: building exterior wall coating, anti-corrosion coating, powder coating, heat-resistant coating, insulation coating, road sign coating, waterproof coating Special functional coatings such as anti radiation coatings. Here are some examples of the application of wet sericite powder in coatings

I. using the screen of sericite, this batch of joints are unqualified products with UV shielding performance to improve the weatherability of the coating

(I): in the exterior wall latex coating system, add sericite powder of different proportions and specifications to carry out artificial aging resistance test. The test formula is shown in Table 1, and the test results are shown in Table 2. Table 1 test formula of sericite powder in exterior wall emulsion paint

Table 2 blank and performance test table of adding different specifications of sericite powder

this test is carried out in accordance with gb/t 1865, and the result evaluation is carried out in accordance with gb/t 1766. From the above test data, it can be seen that adding sericite to the exterior wall emulsion paint can greatly improve the weatherability of the film, and the contribution of dry sericite powder and illite sericite powder to the weatherability is also a certain gap compared with wet sericite

(II): wet sericite powder is added to the powder coating of pure polyester system. The test formula is shown in Table 3, and the test results are shown in Table 4: Table 3: test formula of sericite powder in the powder coating of pure polyester system

Table 4: performance test table of sericite powder in the powder coating of pure polyester system

remarks: curing condition 200 ℃ 10min

from the above data, it can be seen that in the pure polyester powder coating, Adding sericite powder can not only improve the appearance of paint film, improve pencil hardness, enhance water resistance, but also greatly improve the weather resistance of paint film. See Figure 5 for the specific test data:

take the lattice number of one sample from the point to the left

from the data in Figure 5, it can be seen that in the case of artificial accelerated aging test without sericite, the coating will mutate at 800 ~ 900 hours, and the gloss will decline sharply. After sericite is added, it can effectively inhibit the mutation, so that the coating can still maintain a high light retention and increase the aging resistance of the coating

II. Use the sheet superposition barrier function of Sericite to improve the water permeability of the paint film

add sericite powder of different specifications and proportions to the epoxy zinc rich primer paint system for routine item detection. See Table 5 and table 6 for the specific experimental methods. The paint mixing ratio is: A is worth mentioning: B =10:1, See Table 7 for test results table 5: test formula of component a

Table 6: test formula of component B

remarks: xylene: epoxy hexanone =3:1

Table 7: performance test table of epoxy zinc rich primer added with Sericite of different specifications and proportions

remarks: "★": it refers to that after 336h of water resistance test, the sample is not bad, and the test is stopped

from the above test results, it can be seen that sericite sheet superposition barrier function can significantly improve the salt water and salt fog resistance of the paint film, and wet sericite powder is better than dry sericite powder and illite sericite powder

third, using the matting property of Sericite can replace the matting agent and reduce the formulation cost

sericite has a certain matting effect. Making good use of this can replace the use of matting agent, reduce the cost of coating formula and improve market competitiveness. Specific application examples are as follows: Table 8: test formula and performance test table

it can be seen from the above table that changing 100 BaSO4 into sericite in Formula 3 has a lower gloss than adding 10 matting agent in formula 4, but in terms of cost, formula 3 is nearly 500 yuan a ton lower than formula 4. (end)

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