Mica Application in Paint and Coating Industries

(1) Barrier Effect

In paint film, flaky filler will form a basically parallel arrangement, thus strongly preventing the penetration of water and other corrosive substances, and if using high-quality mica powder( diameter-thickness ratio being at least 50 times, preferably 70 times), this kind of penetration time will normally be extended by 3 times. As the mica filler is much cheaper than the special resin, it has a very high technological and economic value.

In short, using high-quality mica powder is an important approach to improve the quality and performance of anti-corrosion and outer wall coatings. During the coating process, before the paint film is solidified, mica chips will lie down under the surface tension and then automatically form paralleled to one another and to the surface of paint film. The orientation of this kind of parallel arrangement is right perpendicular to that of corrosive substances’ penetrating paint film, thus playing its barrier effect to the most. The problem is that the flaky mica structure must be perfect, as foreign industrial enterprises set the standard that diameter-thickness ratio should be at least 50 times, preferably more than 70 times, otherwise the results will not be desirable, because the thinner the chip is, the larger the effective barrier area with the unit volume of the filler, on the contrary, if the chip is too thick, then it can not form many barrier layers. That’s why the granule filler simply doesn’t possess this kind of function. Also, perforation and avulsion on the mica chip will seriously affect this barrier role (corrosive substances can easily leak in). The thinner the mica chip is, the larger the barrier area with the unit volume of the filler. Better effect will be achieved with moderate size (too thin is not always good).

(2) Improving Physical and Mechanical Properties of the Film

Using wet ground mica powder can improve a series of physical and mechanical properties of paint film. The key is the morphological characteristics of fillers, namely, the diameter-thickness ratio of flaky filler and length-diameter ratio of fibrous filler. Granular filler acts like sands and stones in the cement concrete to enhance the steel.

(3) Improve the Anti-Wear Property of the Film

The hardness of resin itself is limited, and the intensity of many types of filler is not high (e.g., talcum powder). On the contrary, mica, one of the components of granite, is great in terms of its hardness and mechanical strength. Therefore, adding mica as filler, the anti-wear performance of coatings can be significantly improved. That’s why mica powder is preferably used into car paint, road paint, mechanical anti-corrosion coatings and wall coatings.

(4) Insulation

Mica, with a very high rate of electric resistance (1012-15 ohm· cm), is in itself the best insulation material and it is a publicly known technology to use it to improve the insulation property of paint film. What’s interesting is that when working with the composite material of organic silicon resin and organic silicon and boric resin, they will convert to a kind of ceramic substance with good mechanical strength and insulating property once encountering high temperature. Therefore, wire and cable made of this kind of insulating material can still maintain its original insulation property even after fire, which is quite important for the mines, tunnels,special buildings and facilities, etc.  

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(5) Anti-Flaming

Mica powder is a kind of very valuable fire-retardant filler and it can be used to make flame-retardant and fire resistant paint if applied with an organic halogen flame retardant.

(6) Anti-UV and Infrared Rays

Mica is very excellent in shielding ultraviolet and infrared rays, etc. So adding wet ground mica powder into the outdoor paint can significantly enhance the film's anti-ultraviolet performance and slow down its aging. By its performance of shielding infrared rays, mica is used in making heat preservation and thermal insulation materials (such as paint).

(7) Reducing Sedimentation

Suspension performance of wet ground mica is very excellent. The extremely thin and tiny chips can suspend permanently in a medium without hierarchical sedimentation. Therefore, when using mica powder as filler instead of that will easily subside, the stability of coating storage will increase significantly.

(8) Heat Radiation and High-Temperature Coatings

Mica has a great capability of radiating infrared rays. For instance, when working with iron oxide, etc., it can create excellent thermal radiation effects. The most typical example is its application in spacecraft coatings (reducing the temperature of the sunny side by tens of degrees). Many painting outfitting of heating elements and high-temperature facilities all need to use the special paint containing mica powder, because such coatings can still be workable under very high temperatures, such as 1000 ℃ or so. At that time the steel will become red-hot, but the paint remains unharmed.

(9) Gloss Effect

Mica has good pearlescent gloss, hence, when using large-size and thin-sheet mica products, materials, such as paints and coatings, can be shiny, glossy or reflective. On the contrary, super-fine mica powder can make repeated and mutual reflection within the materials, thus creating delustering effect.

(10) Sound and Vibration Damping Effects

Mica can significantly change a series of physical modulus of the material as well as form or alter its viscoelasticity. Such materials can effectively absorb vibration energy as well as weaken shock and sound waves. In addition, shock waves and sound waves will form repeated reflections between mica chips, which also results in weakening the energy. Therefore, wet ground mica is also used to prepare sound and vibration damping materials.

Post time: Jun-23-2020