GB/T 1741-2020Test method for determining the resistance of paints film to mold (English PDF)

6.2 Sterile water Accurately weigh

0.005 g of dispersant (such as Tween 80) and add it to 100 mL of water; stir evenly; divide it into colorless glass test tubes (5.21) at a cultivate at 28 °C ~ 30 °C for 7 d ~ 14 d; when the surface of the medium is covered with mold spores, add 10 mL of sterile water (6.2); in the biological safety cabinet (5.8), use a sterile inoculation loop (5.16) to gently scrape mold spores on the surface of the mold culture, under aseptic operating conditions, to make into a mold spore suspension. Pour the mold spore suspension into a 125 mL sterile triangular flask (5.15) with a stopper, which has been pre-filled with 45 mL of sterile water (6.2) and 10 ~ 15 sterile glass beads (5.17); vigorously shake the sterile triangle flask (5.15) to break up the spore clusters and release mold spores from the fruit body. Place a sterile glass funnel (5.18) with sterile fiber filter paper (5.19) on a sterile triangular flask (5.15); pour the shaken mold spore suspension into a sterile glass funnel (5.18) to filter and remove mycelium and medium fragments. Centrifuge the filtered mold spore suspension at a speed of 4 000 r/min under aseptic conditions; remove the supernatant; add 10 mL ~ 50 mL of sterile water (6.2) to the spore precipitate; mix well; then, centrifuge to get the mold spore precipitate; re-add sterile water to mix; centrifuge again to obtain mold spore precipitate. Use the nutrient solution (6.3) to dilute the mold spore precipitate; use a blood counting chamber (5.14) or other methods to determine the concentration of mold spores; dilute so that the concentration of mold spores in the suspension is 0.8×106/mL ~ 1.2×106 /mL. Each kind of prepared mold spore suspension can be stored in a refrigerator (5.10) at 4 °C ~ 10 °C for no more than 4 days. Before the test, mix each prepared mold spore suspension in equal volume to obtain a mixed mold spore solution.

7.2 Sample Take samples of the product according to GB/T 3186; the sampling amount shall be determined according to the inspection requirements.

7.3 Preparation of samples

7.3.1 Test sample Unless otherwise specified, use aluminum plates, glass plates and other substrates that are not easy to rust and absorb moisture; the size is 50 mm × 50 mm; the thickness is at least 1 mm. Unless otherwise specified, process each test plate according to the provisions of GB/T 9271-2008; aluminum plate and other metal substrates can be polished with suitable sandpaper. Then, apply and maintain 3 test plates as test samples according to the product regulations. The paints film of the outdoor product test sample is subjected to an aging test according to the provisions of

8.2.1 in GB/T 23987-2009 before the resistance test to mold; the irradiance is

0.83 W·m-2·nm- 1; the test time is 100 h. Unless otherwise agreed, the test sample shall be adjusted for at least 4 h under the conditions that are specified in GB/T 9278 before the test.

7.3.2 Control sample 3 sheets of sterile fiber filter paper (5.19) whose size is (50×50) mm.

7.4 Inoculated culture

7.4.1 Petri dish method Pour about 20 mL of nutrient agar medium (6.4) into a sterile petri dish (5.13). When the medium is solidified, under aseptic conditions, place 3 test samples and 3 control samples respectively in the center of the surface of the petri dish that contains the culture medium. Use a sterile sprayer (5.11) to evenly spray

0.4 mL ~

0.6 mL of mixed mold spore solution (7.1.3) on the surface of each test sample and control sample and the surface of the culture medium, so that the entire test sample and the surface of the control sample and the surface of the culture medium are wet. Place the inoculated test sample and control sample in a constant temperature and humidity incubator (5.1); incubate for 7 days at a temperature of 25 °C ~ 30 °C and a relative humidity of not less than 85%; then, visually inspect the growth of mold on the control sample; the three control samples shall have mold growth; otherwise, the test is invalid and the test shall be repeated. If mold growth can be seen on each control sample, continue to incubate the test sample and the control sample for 28 days and evaluate the result according to 7.5. The cultivation time can be extended to 56 days upon agreement by the relevant parties.