Coatings - Determination of needle penetration resistance performance

The scratch resistance performance of coatings is one of the important indicators to evaluate the mass and durability of coatings such as Paints and varnishes. This article will introduce the measurement method of the scratch resistance performance of coatings, including the scope of application, required instruments and materials, and detailed measurement steps.

1. Scope and description

This method is suitable for the determination of the scratch resistance performance of single coatings or composite coatings of products such as Paints and varnishes. The measurement principle is based on the minimum load or work required for the scratch needle to penetrate the paint film to indicate the scratch resistance performance of the paint film. Test results are usually expressed as pass or no pass.

2. Instruments and materials

Scratch test instrument: It can be electric or manual. The electric instrument includes a motor-driven skateboard, a steel needle holder with weight and a conductive indicating device. Manual instruments should have similar functions.

Scribing needle: a hemispherical needle of hardened hard steel with a diameter of 1 mm, fixed on the scribing rod.

30 times magnifying glass.

3. Determination method

Determination of fixed load:

Use 30x magnifying glass to inspect the needle to make sure it is smooth and hemispherical with no obvious abrasion or dirt.

Secure the scribing needle to the collet so that the tip is perpendicular to the coating.

Clamp the coating of the specimen up on the sliding plate of the Scratch meter, making sure that the long side of the plate is parallel to the scratch direction.

Place the weight on the stent above the scribe to apply the given load.

Open the instrument or push the sliding plate of the instrument evenly by hand to scratch the coating of the test plate.

Remove the test plate, check whether the coating is penetrated, or use the conductive pointing device of the electric instrument to judge.

Determination of minimum load for penetrating coatings:

Follow the above steps for a scratch test, each scratch should be performed on the unscratched part.

Start with a smaller load and gradually increase the load until the coating is just penetrated.

With this last load, the unscratched portion of the repeability test and a new test plate to determine the minimum load across the coating.

4. Presentation of results

Determination of fixed load: According to whether the coating is penetrated under a given load, it is expressed as pass or no pass.

Measurement of the minimum load of the coating: the minimum load when the coating is scratched as the hardness value of the coating.

5. Reference standard

National standard CB/T 9279 "Paints and varnishes scratch test".

Scratch resistance performance measurement of coatings is a key step in ensuring coating mass and performance. It can help manufacturers and users evaluate the suitability and durability of coatings to meet the needs of different Applications. Through this measurement method, it is possible to better understand the performance of coatings in the face of various scratch and abrasion situations, thereby providing strong support for coating selection and application.