How to test the heat resistance of ink?

(1) Purpose and definition.

Some inks need to be heated and dried after printing, such as metal (iron sheet, hose) printing inks, glass printing inks, etc. Therefore, the heat resistance of such inks is very important.

It can be understood that the heat resistance of the ink mainly depends on the pigment and the binder itself, that is to say, the heat resistance of the pigment and the binder will determine the heat resistance of the ink.

As for the heat resistance of the binder, it almost refers to whether the color becomes darker after it is heated, or it turns from light white to brownish yellow. Of course, the determination of the heat resistance of the binder can be done by coating it on a white metal sheet, and then observing the degree of color change after heating and baking.

Generally speaking, except that the heat resistance of some light-colored inks such as white mainly considers the content of the binder, for most colored inks, the heat resistance still depends on the binder.

(2) Appliances and materials.

1. Utensils

(1) Minor tune clamor knife.

(2) Analytical balance <one thousandth).

(3) Small rubber wheels (synthetic cunning is better).

(4) Glass plate for ink distribution.

(5) Oven.

2. Materials.

(1) New tin-plated iron sheet ((about 3×15 cm²).

(2) Drying oil (one can be fixed arbitrarily).

(3) Method.

Take 4.75 grams of ink to be tested and 0.25 grams of drying oil with a balance scale, put them on a glass plate and use a small ink knife to fully mix them evenly.

Take out a small amount of evenly mixed ink, put it on a glass plate and roll it evenly with a small rubber roller, and then apply the ink roller on the rubber roller to the tin-plated iron sheet until the ink completely covers the metallic luster of the iron sheet.

Cut the iron sheet coated with ink into six small pieces, and bake them in a constant temperature oven at 60°C, 80°C, 100°C, 120°C, 140°C and 180°C for 30 minutes.

Take a piece baked at 60°C for 30 minutes as the standard, compare it with the pieces baked at other temperatures for 30 minutes, observe its discoloration and fading, and use the one that does not change color or fade at the highest temperature to indicate the ink heat resistance.

(4 ) Matters needing attention.

1. If the tested ink itself can be dried at 60°C for 30 minutes, it is not necessary to add drying oil.

2. When the miscibility between the engraving ink and the drying oil is poor, you should choose a suitable drying oil.

3. The measurement temperature can be determined according to actual needs.

4. The heat resistance evaluation of the ink also needs semi-rich experience. Sometimes it changes greatly when it is just taken out of the oven, and gradually returns to its original state after cooling.

5. The thickness of the coating film needs to be consistent, otherwise the comparability will not be accurate.