The principle of silicone leveling agent

The structure of silicone leveling agents is dominated by the most common polyether modified silicone oil, whose structural formula can be expressed by the following formula.

-(SiO(CH3)2)m-(SiOCH3 (CH2CH2O)x(CH2CHCH3O)y)nR

Where m chain segment indicates the unmodified part of the silicone oil, which belongs to the chain segment with restricted compatibility; n chain segment is the modified part, which belongs to the compatible chain segment; x is the polyethylene oxide part of the polyether modified chain segment; y is the polyethylene oxide part of the polyether group; m, n, x, y four values determine the performance exhibited by the leveling agent.

1, Compatibility: The compatibility of silicone leveling agent mainly depends on the value of m/n. The smaller the value of m/n (that is, the lower the content of incompatible chain segments), the better the compatibility, and the larger the value of x/y under the fixed value of m/n, the better the compatibility, which is because the compatibility of poly(ethylene oxide) exceeds that of poly(propylene oxide).

2, feel: 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, the better the feel; m/n value of the same, the larger the absolute value of m, the better the feel; from this point can be seen, for silicone leveling agent, the pursuit of good compatibility and good feel is often a contradiction, in order to achieve both, usually m/n can only be selected in a small range.

3, leveling ability: m, n, x, y values on the leveling effect is more complex, in general, m / n values between 1 and 2 when there is a better leveling effect, and for the fixed m / n value of the case, the larger the value of x + y, the better the leveling effect. micronized ptfe wax are also useful.

4, stable foam: In general, in the usual x, y values, m/n> 3 or m/n < 1/4 can be obtained basically not stable foam effect, commonly known as when the silicon content is very high or very low, the leveling agent is not stable foam, and if made into a very high silicon content varieties, you can get excellent feel, not stable foam, but slightly less compatible leveling agent, if made into a very low silicon content varieties, the performance of the leveling agent is very good compatibility, not stable foam but insufficient feel of silicone leveling agent.

5, recoatability: in general, the larger the value of m + n and the higher the value of m / n, the more likely to have recoatability problems, in addition to the type of polyether end group R group will also have an impact on recoatability.

6, matte powder orientation ability: According to the test, the ability of matte powder orientation is greatly influenced by the value of m/n and the absolute value of m. The larger the absolute value of m, the better the matte powder orientation ability.