Surfactant can prevent or solve many problems in coating technology

2021-03-31 15:56:59

The paint may produce high surface tension during spraying and maintain the high surface tension until sprayed onto the bottom, so the initial wetting effect is not good. Surfactants can be used to change this state, but it is necessary to choose them because the amplitude and speed of surfactant reducing dynamic surface tension are different. The effect of water soluble surfactants on reducing dynamic surface tension is very small, but not easy to dissolve in water. The surfactant which forms micelles is often very effective. For example, diisophonate sulfonate and pluronicl61 (BASF Wyandotte products, polypropylene glycol and ethylene oxide additive nonionic surfactants) are not easy to dissolve in water, and the dynamic surface tension can be reduced to 4.3 and 3.6dyne/cm in acrylic emulsion paint. Water soluble surfactants such as sodium dodecyl sulfate and sodium dodecylbenzene sulfonate can only be moved in this coating system. The surface tension of the state decreased to 13.4 and 13.7dyne/cm.

Using surfactant can prevent or solve many problems in coating technology. These problems can be divided into two types, namely, the defects caused by surface tension and the dispersion of pigments. Many surface defects such as shrinkage, stain reflection, depression, blister, chapped, bead shrinkage and Bernal swirl cavity are caused by surface tension. Other problems such as floating color, hair, poor color, poor polish and poor gloss are caused by poor dispersion of pigments.

The difference of surface tension (gradient) on the top and bottom of the coating surface can cause shrinkage, depression, blister and bead shrinkage. The surface tension gradient may be caused by low surface tension impurities such as fingerprints, small oil droplets, solvent swelling gel particles, etc., and may also be caused by temperature difference or concentration gradient on both sides of the surface. The concentration gradient will make the material flow from low surface tension to the area with high surface tension. The key to prevent this phenomenon is to make the surface uniform and eliminate the surface tension gradient. Therefore, one of the common methods is to cover the surface with a surfactant to produce a lower and consistent surface tension.

Some defects such as blister may be caused by poor initial wetting of the base material or the anti wetting effect after coating. In addition to cleaning the base material and improving its wettability, the more common method to solve this problem is to add wetting agent to the coating.