Detailed explanation of the method for measuring film Hardness - super detailed

This method is suitable for the determination of the hardness of the coating film. It is a method for measuring the hardness of the coating film by scratching the hardness of the coating film with a pencil of known hardness label. There are two test methods: instrument method and manual method.

(1) Instrument method

Scope and description

By using a pencil Hardness Tester, a group of pencils with known hardness is used to measure the relative hardness of the coating film surface.

Instruments and Materials

(1) Pencil Hardness Tester There are desktop and portable pencil Hardness Testers, as shown in Figure 1-4-7 and Figure 1-4-8. Portable is a small mechanical trolley. The metal base with two pulleys on both sides can move freely on the sample. There is a round hole at an angle of 45° in the middle of the base and a clip for fixing the pencil, which can make the pencil Fixed with the horizontal plane at an angle of 45°, the self-weight of the instrument should ensure that the force on the pen tip in the horizontal direction is (7.5±0.1) N; (2) Zhonghua brand high-end drawing pencils are marked as 9H, 8H, 7H, 6H, 5H , 4H, 3H, 2H, H, F, HB, B, 2B, 3B, 4B, 5B, 6B, among which 9H is the hardest, 6B is the softest, and the hardness decreases from 9H to 6B; (3) 400# water sandpaper; ( 4) Pencil sharpener; (5) Great Wall brand advanced drawing eraser.

test methods

(1) First use a pencil sharpener to cut off the wooden part of the pencil, so that the lead is cylindrical and expose about 3mm (do not cut the lead), then make the lead vertically draw a circle on the 400# water sandpaper, and slowly Grind until the pencil tip is ground flat and the edges are sharp (the edges must not be chipped or chipped).

(2) Place the sample with the coating film facing up on the testing machine horizontally, fix the sample, and fix the pencil so that the lead and the vertical line where the weight of the testing machine passes through the center of gravity form an included angle of 45°.

(3) Adjust the balance weight so that the pencil load on the sample plate is not positive or negative. Add a weight of (1.00±0.05) kg to the weight rack, loosen the fixing screws, and slowly make the tip of the pencil lead touch the painted surface.

(4) Shake the handwheel at a constant speed, so that the template can draw a scratch of about 3mm horizontally toward the opposite direction of the pencil lead at a moving speed of 0.5mm/s. Change the position and scratch five times. Before each scratch, the pencil lead should be rotated 180° before use or re-smoothed.

(5) To use a portable pencil Hardness Tester, place the trolley on the sample plate, put the treated pencil into the trolley and fix it so that the tip of the pencil contacts the surface of the sample. Push the trolley at a constant speed so that its stroke on the sample plate is 6.5 mm.

The result shows

The results of pencil hardness are divided into two types: scratches and scratches. Scratch means that when the paint film is scratched with a pencil, there are scratches on the paint film but does not hurt the substrate; scratch means that the paint film is scratched by the pencil to expose the substrate.
When judging, if more than two (including two) of the five scratches appear to be damaged, then the pencil with the next grade of hardness mark will be used as the pencil with the hardness mark of the pencil until the pencil with less than two of the five scratches is damaged. membrane hardness.

Reference standard

National Standard GB/T 6739 "Pencil Method for Determination of Paint Film Hardness"

(2) Manual method

Scope and description

The manual method is easy to operate and has strong adaptability. It can be used in laboratories and construction sites, but it is more suitable for construction sites.

 2. Instruments and Materials

(1) Zhonghua brand advanced drawing pencil: the same as the instrument method; (2) 400# water sandpaper; (3) Pencil sharpener; (4) Great Wall brand advanced drawing eraser.                       

3. Measurement method

(1) Use a pencil sharpener to sharpen the pencil until the 3mm cylindrical core is exposed, and grind it vertically on 400# water sandpaper until the edge is sharp.

(2) Place the sample coating film upwards and horizontally on the operating table, hold a pencil so that it forms an angle of 45° with the coating film, apply sufficient and uniform pressure downwards and forwards (the pencil lead does not break), and the pencil moves forward The speed is about 1mm/s and the scratch length is 1cm. As shown on the right.

(3) For each scratch, the pencil should be rotated 180° before use or re-smoothed, and the pencil with the uniform hardness mark should be scratched five times repeatedly.

The result shows

Same as "instrument method".

Reference standard

National Standard GB/T 6739 "Pencil Method for Determination of Paint Film Hardness"