Drying time plays a crucial role in the coatings industry. The drying process from liquid to solid is divided into three stages: surface drying, actual drying and complete drying. The control and determination of this process is essential to ensure the quality and performance of the coating. In this article, we will delve into the concept of drying time, the different measurement methods, and its importance in the coatings industry.

concept
Drying of paint refers to the process from the application of liquid paint to the formation of a strong film. The process can be divided into three key stages: surface drying, actual drying, and complete drying. Surface drying means that the surface of the paint begins to dry, usually as the outer layer of the paint film begins to become dry, but the interior is still wet. Actual drying means that the entire coating film has been dried, including the interior. Completely dry means that all solvents in the coating film have evaporated and the film has been fully cured.

In order to determine the drying time of the coating, usually only the two stages of surface drying and actual drying are measured. This is because the time required for complete drying is relatively long and difficult to determine quickly. There are a variety of methods for the determination of surface dryness and actual dryness, and different methods can be selected according to different standards and needs.

Several methods for determination of coating drying time

Determination method
A common method for determining surface dryness is the blowing cotton ball method. According to the provisions of GB/T 1728-79 standard, the operation method is to place a absorbent cotton ball on the surface of the paint film, and then blow the cotton ball with the mouth. If you can blow away the cotton ball without leaving the silk, then the surface can be considered dry. It is necessary to record the maximum time required to reach surface drying, or to determine whether the coating is qualified according to the specified surface drying time.

The cotton ball blowing method is a simple and effective method, which is especially suitable for the rapid determination of coating surface dryness. It can help paint manufacturers ensure that after paint application, the surface has dried enough to allow for the next step of treatment or operation.

Method for determining actual dryness

There are many options for determining actual dryness, and one common method is the filter paper method. According to the GB/T 1728 standard, the operation method is to place a piece of filter paper or a absorbent cotton ball on the paint film, and then use a drying tester (drying weight, 200g) to press it on the paint film. After 30 seconds, remove the tester and turn the template over. If the filter paper can fall freely or there is no cotton ball trace and loss of light on the paint film, then it can be considered that the actual drying has been achieved. It is necessary to record the maximum time required to achieve actual drying, or to determine whether the coating is qualified based on the specified actual drying time.

The filter press paper method is a common method of actual drying measurement that can help ensure that the entire coating film has dried to meet specific quality requirements. This is crucial for the use of coatings in different environmental conditions, as coatings that are not completely dried can cause quality problems.

Several methods for determination of coating drying time

Instrumental method

In addition to blowing cotton ball method and filter paper method, a variety of automatic drying time measuring instruments can be used to determine the drying time of the coating. These instruments can help observe changes in the different stages of the drying process, allowing for a more accurate determination of drying times.

Take the stroke method as an example, it uses the clock motor to drive a rotating arm with a stroke needle, marking a circular track with a fixed diameter on the paint film. When the paint film is cut by the needle into a diamond shape, the surface drying begins; Actual drying begins when the split film terminates and the needle track remains on the film surface. Eventually, when the trace disappears, the coating film can be considered completely dry.

These instrumentation methods offer greater accuracy and repeatability for coating manufacturers, especially in applications where coatings need to meet stringent quality requirements, such as the automotive manufacturing and aerospace industries.

The importance of drying time
Drying time is critical to the coatings industry. It can not only affect the quality and performance of the coating, but also affect the production efficiency and cost control. Here are a few important aspects of drying time:

The accurate determination of the drying time ensures that the coating film has the desired properties such as adhesion, hardness and wear resistance when used. Insufficient drying time may result in insufficient viscosity of the coating film, which is easy to flake or damage.

Several methods for determination of coating drying time

Knowing the drying time of paint can help manufacturers better plan the production process, reduce waiting time, and improve production efficiency. This is especially important for mass production of paint products.

The drying time of the paint may be different under different environmental conditions. Knowing the drying time can help you choose the right paint for your particular application.

Accurate measurement of drying times can help control energy consumption during coating production, thereby reducing production costs.

In general, drying time is a key parameter in the coating industry, which has a significant impact on coating quality, production efficiency and cost control. Therefore, coating manufacturers need to carefully select the appropriate determination method and ensure the accurate determination and control of drying time to meet market demand and quality standards.