GB/T 33374-2016Ultraviolet curable coatings - Determination of volatile content (English PDF)

3.1 Ultraviolet curing; UV curing

The hardening process of coatings exposed to UV radiation.

3.2 Processing volatiles

Mass loss of the sample during the curing process, under the specified test conditions (i.e., the conditions that simulate the actual industrial ultraviolet curing process).

3.3 Potential volatiles

Mass loss of the UV-cured sample in the process of drying at (110±2) °C for 60 min.

4.1 Metal flat-bottom vessel

Diameter (75 ± 5) mm, edge height 5 mm or ensuring that the sample does not overflow.

Alternatively, it can be a vessel of different diameter, while the sample weight shall vary according to the diameter.

Note: The viscous coatings can also be made of aluminum foil of a thickness about 0.1 mm. Cut it into a rectangle of a size about (100±10) mm × (300±10) mm that can be folded in half; lightly squeeze the two folded parts to spread the viscous liquid completely.

4.2 Oven

Warning – In order to prevent explosion or fire, samples containing volatile substances shall be handled with care, and shall be implemented in accordance with relevant national regulations.

In order to ensure the safety of the test, a forced convection oven shall be selected, which can be maintained within the range of ±2 °C of the specified or agreed temperature, and be equipped with a horizontal shelf. Alternatively, a natural convection oven, which is equipped with perforated metal baffles at 1/3 the height of the working chamber, can be used.

4.3 Desiccator

Loaded with a suitable desiccant, such as dry silica gel that has been impregnated with cobalt chloride.

4.4 Balance

Accuracy 0.1 mg.

4.5 Syringe

Disposable syringe, of capacity 1 mL.

4.6 Ultraviolet curing equipment

Ultraviolet curing equipment shall meet the following conditions:

-- Spectral range: >=250 nm, main band wavelength 365 nm;

75 – standard diameter of the vessel, in millimeters (mm).

Note 1: When mixing samples, manual stirring can not only ensure that the samples are evenly mixed, but also avoid the generation of air bubbles.

Note 2: The surface of the syringe – after taking the sample – shall be wiped clean; the sample shall not be left in the neck of the syringe, which can be solved by pulling up the plug of the syringe. After injecting the sample, do not wipe the tip of the syringe; instead, remove the sample on the tip by pulling up the plug of the syringe; cap and reweigh the syringe. Weigh the sample (accurate to 0.1 mg) by the decrement method.

Note 3: If the sample is incompatible with acetone, tetrahydrofuran or a mixed solution of acetone and tetrahydrofuran can be used to dissolve and disperse.

Note 4: Spread the to-be-tested sample on the bottom of the vessel (see 4.1); otherwise, the incomplete curing, due to the excessive thickness of the coating film, will lead to large test results.

Note 5: Disposable gloves (rubber gloves or polyethylene gloves) shall be worn for all weighing operations during the test.

6.4

Immediately after weighing, place the sample in an oven (see 4.2), and bake at (50±2) °C for 30 min.

Note 1: This is a step of simulating the removal of inert solvents in the industrial production stage. Where the sample contains a large amount of solvent, direct curing will lead to a great deviation between the test results and the actual results.

Note 2: Alternatively, if it is known that the volatile content in the sample is less than

3%, the step of 6.4 can be omitted and ultraviolet curing can be carried out directly.

Note 3: If the sample contains volatile reactive diluents (such as styrene, isobornyl acrylate) at 50 °C, the step of 6.4 cannot be carried out regardless of the volatile content.

6.5

Immediately after taking the sample out of the oven, perform the ultraviolet curing according to the curing requirements specified for the to-be-tested sample. After ultraviolet curing, place it at room temperature for 15 min; weigh the mass (m2 ) (accurate to 0.1 mg) of the cured sample and vessel (see 4.1).

Note: In order to avoid the influence of insufficient ultraviolet curing energy on the experimental results, the curing energy can be increased by 50% for a comparative test. If the test results meet the repeatability requirements, the test results shall be accurate. If the test results do not meet the repeatability