The principle of leveling and the principle of the leveling agent

The principle of leveling and the principle of the leveling agent






The principle of leveling and the principle of the leveling agent Posted by: ZHANG Release date: 2012-12-28


I. Leveling agent: Leveling agent is a commonly used coating additive, which can promote the coating to form a smooth, smooth and uniform coating film during the drying process. The leveling agents used for different types of coatings are also different.

Second, the principle of the leveling (migration mechanism): As a leveling agent, generally need to meet the following two points:

1. It has certain compatibility with the system.

2. The surface tension needs to be lower than the system. Both of these points affect the migration of the leveling agent. Only when the leveling agent spontaneously migrates to the surface of the paint film can it be called leveling. The principle of migration is equally applicable to the migration of other auxiliaries. Migration principle: The migration orientation of the leveling agent follows the "lowest energy principle" in physics, that is, from the place where the energy is high to the place where the energy is low. When the coating is applied to the surface of the substrate, two interfaces are formed, namely “substrate-paint film interface” and “paint film-air interface”, so the total energy of the system = (substrate surface tension - film surface tension) + (Paint film surface tension - air surface tension). When the leveling agent is added to the system, if the leveling agent migrates to the “paint film-air interface”, then the total energy of the system = (substrate surface tension - film surface tension) + (leveling agent surface tension - air surface tension) ), due to the surface tension of the leveling agent 3. Principle of the silicone leveling agent: The structure of the silicone leveling agent is mainly composed of the most common polyether modified silicone oil, and its structural formula can be expressed by the following formula: —(SiO( CH3) 2) m—(SiOCH3 (CH2CH2O)x(CH2CHCH3O)y)nR wherein the m segment represents an unmodified portion of the silicone oil and belongs to a segment with limited compatibility; the n segment is a modified portion and belongs to the phase The volume chain segment; x is the polyethylene oxide moiety in the polyether modified segment; y is the polypropylene oxide moiety in the polyether group; m, n, x, y four values ​​determine the leveling agent The performance exhibited, the different sizes of these four values ​​determine the inability of the leveling agent.

1. Compatibility: The compatibility of silicone leveling agent depends mainly on the value of m/n. The smaller the value of m / n (that is, the lower the content of incompatible segments), the better the compatibility. In the case where the value of m/n is fixed, the larger the value of x/y, the better the compatibility, because the compatibility of polyethylene oxide exceeds that of polypropylene oxide.

2. Hand feeling: In the case of fixed xy value, the feel of silicone leveling agent also depends mainly on the value of m/n. The larger the value of m/n is, the better the hand feel is; the same m/n value is. The larger the absolute value of m, the better the hand feel; from this point, it can be seen that for silicone leveling agents, the pursuit of good compatibility and good hand is often a contradiction, in order to achieve both, usually m/ n can only be selected within a small range.

3. Leveling ability: The value of m, n, x, y has a complicated effect on the leveling effect. Generally speaking, the m/n value has a better leveling effect between 1 and 2, but In the case of a fixed m/n value, the larger the value of x+y, the better the leveling effect.

4. Foam stability: In general, under the usual x, y values, m / n > 3 or m / n
5. Recoatability: Generally speaking, the larger the value of m+n and the higher the value of m/n, the more likely the problem of recoatability will occur, and the type of polyether end group R group will also be recoated. Sex has an impact.

6. Orientation ability of matting powder: According to the test, the ability of the matting powder to be oriented is greatly affected by the value of m/n and the absolute value of m. The larger the absolute value of m, the better the ability of the matting powder to orient.



'Leveling principle and principle of leveling agent

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