Sag problems and their solutions

In Coating applications, sag issues can lead to poor film Appearance, which affects product mass. This article will explore the causes of sag and solutions to help address this challenge.

1. Causes of sag

Sag refers to the phenomenon that part of the film flows down during construction, causing the film to leave marks on the surface or hang vertically. Here are some common causes of sag:

A. Coating viscosity reduction: During construction, in order to achieve levelling, it is usually necessary to reduce the viscosity of the Coating. However, if the viscosity drops too fast or too much, the Coating will flow on the surface, forming a sag.

B. Solvent evaporation rate is too fast: The solvent in solvent-based paints evaporates during construction. If the solvent evaporates too fast, the viscosity of the Coating may decrease rapidly during Spreader, resulting in sagging.

C. Temperature and Humidity Effects: Temperature and Humidity of the construction environment can also affect sag. Higher Temperature and Humidity may cause Coatings to flow faster, increasing the risk of sag.

D. Coating formulation problem: Various ingredients in the Coating formula, such as rheological aids, pigments and Resin, may have an impact on the flow. Inappropriate formulations may lead to Coating instability and sagging.

2. How to solve the sag problem

To avoid or mitigate sag problems, the following steps can be taken:

A. Control viscosity: Controlling the viscosity of the Coating is the key to preventing sagging. To ensure that the viscosity does not decrease rapidly during construction, you can use suitable rheology additives or adjust the viscosity of the Coating.

B. Controlling solvent evaporation rate: For solvent-based paints, it is important to control the evaporation rate of the solvent. Slower evaporation rates can be achieved by adjusting the solvent composition or using lame plating equipment, thereby reducing the risk of sag.

C. Adjust construction conditions: Temperature and Humidity are important factors in construction conditions. In a high temperature and high humidity environment, viscosity and flowability need to be controlled more carefully to prevent the occurrence of sag.

D. Reasonable Coating Formulation: Coating formulations should be carefully designed to ensure compatibility and stability between the various ingredients. Appropriate rheology additives and stabilizers can help alleviate sagging problems.

E. Use the appropriate Spreader method: Different Spreader methods have different effects on streaming hanging problems. Choosing the appropriate Spreader method can reduce the risk of sag. For example, lame plating is often easier to control sag than brushing.

F. Spreader thickness control: Controlling the thickness of the Spreader can also alleviate the sagging problem. Thicker films are not prone to sagging, so the amount of Spreader can be adjusted to suit the needs.

Conclusion

Sag is a common problem in Coating applications, but it can be effectively mitigated or avoided through reasonable control and construction methods. For applications that require high-mass painting, special attention needs to be paid to sag issues to ensure that the mass and Appearance of the final film meet the requirements. Correct Coating selection, construction condition control and Spreader method selection are all key factors in solving sag problems.