Comparison of film adhesion determination methods

The measurement of coating adhesion is of great significance in the coatings industry, as it evaluates the physical and chemical interactions between the coating and the substrate. This article will discuss the measurement methods and significance of coating film adhesion, and conduct an in-depth analysis of the advantages, disadvantages and applicable scenarios of four different measurement methods.

Experimental principle

The measurement of coating film adhesion aims to observe the damaged state of the coating film by applying destructive external force (crossing, circling, twisting, pulling apart), so as to evaluate the ability of the coating film to not fall off from the substrate. This measurement method uses different instruments and steps based on experimental principles, such as sharp blades, circle adhesion testers, twist-off adhesion testers, tensile testing machines, etc.

step method

The determination of coating film adhesion includes cross-hatch method, circle method, incision method, twist-off method and pull-off method, etc. Among them, the cross-hatch method evaluates the adhesion by cutting the surface of the coating film to form small squares, the circle method uses a circle line pattern to evaluate the adhesion, the notch method uses a variety of intersecting cuts to observe the adhesion, and the twist-off method determines the adhesion of the coating film. The force required to twist the base plate apart, while the pull-apart method applies a uniform pulling force in the test to determine the adhesion between coatings.

1. Cross-hatch method:

Preparation: Obtain the test sample and make sure the sample surface is dry and clean. Prepare cutting tools, tape, etc.

Experimental steps:

1. Use a cutting tool to cut 6 parallel cuts on the surface of the coating film, cutting through the entire depth of the coating film.

2. Make 6 more cuts perpendicular to the direction of the previous cut to form small squares.

3. Apply the tape to the entire grid, then peel it off at the smallest angle, and observe the proportion of the area where the paint film is peeled off.

4. Based on the peeling off of the coating film, refer to the adhesion level for evaluation.

2. Circle method:

Preparation: Prepare adhesion tester and test samples.

Experimental steps:

1. Use an adhesion tester to draw a circular line pattern of a certain length and overlapping in sequence on the coating film.

2. According to the intactness of the circled part of the coating film, the adhesion level of the coating film is evaluated in turn.

3. Incision method:

Preparation: Prepare cutting tools and test samples.

Experimental steps:

1. Use a cutting tool to make cuts of different sizes to form cuts of different areas on the paint film.

2. Adhesion is evaluated based on the size of the cut and the extent to which the coating film is peeled off.

4. Twist method:

Preparation: Prepare the twist-off adhesion tester, test sample, and adhesive.

Experimental steps:

1. Use adhesive to bond the probe of the measuring instrument to the coating film of the sample to be measured.

2. Twist the instrument 90° with appropriate force and measure the torque required when the paint film is twisted apart, which is equivalent to the twist-off adhesion of the paint film under test.

5. Pull-apart method:

Preparation work: Prepare the pull-out adhesion tester, test piece and adhesive.

Experimental steps:

1. Apply a uniform tensile force to the bonding surface of the sample to determine the force required per unit area between coatings or when the coating and substrate are pulled apart.

2. According to the operating procedures of the tensile testing machine, the specimen is stretched until failure, and its adhesion and failure mode are assessed.

Method comparison

When comparing different measurement methods, we need to consider the advantages and limitations of each. The cross-hatch method, circle method and notch method are relatively simple to operate, and the results are easy to observe and judge, but sometimes they cannot fully accurately represent the adhesion performance of the coating film. The twist-off method and the pull-off method require more complex instruments and operating steps, but they can more accurately evaluate the bond between the coating film and the substrate, and are suitable for different construction scenarios and laboratory conditions. Taken together, various determination methods have different advantages in practical applications, and the selection of an appropriate method depends on the actual situation and the coating film properties that need to be evaluated. In the coatings industry, accurate assessment of coating film adhesion is crucial for product quality control, so appropriate measurement methods need to be selected according to different scenarios.

Meaning and application

Film adhesion is directly related to the durability and performance of the coating. Excellent adhesion means that the coating film can firmly adhere to the surface of the substrate, providing better protection and decorative effects. In practical applications, the correct measurement of coating adhesion can guide product design and process flow, and improve product quality and service life. There are various methods for measuring coating film adhesion and each has its own characteristics. It is necessary to select the appropriate method according to the actual situation and needs. Accurate assessment of coating film adhesion can help guide coating production and application, improve coating quality, and extend product service life.