This method mainly simulates the environmental conditions of mold growth in nature, and designs accelerated tests according to the physiological characteristics of mold growth. Inoculate the mold spores on the specimen surface, then place the specimen in an environmental condition suitable for mold growth, and observe the growth of mold on the specimen surface. The mold resistance of the paint film is graded according to the degree of mold on the specimen surface.
01.Scope and description
This standard is applicable to the determination of mold resistance of architectural paint film, and the determination of mold resistance of other types of paint film can be referred to in this standard.
02. Instruments and materials
Thermostatic and humidity incubators, incubators, high-pressure steam sterilization pots, dry heat sterilization boxes, balances, pH meters, centrifuges, biosafety cabinets, microscopes, refrigerators, sprayers, measuring cartridges, blood cell counting plates, triangular bottles, vaccination rings, glass beads, glass funnels, fiber filter paper, beakers, colorless glass tubes, micrometers, micrometers.
03. Measurement method
Tank fluid aseptic inspection
(mikrocount® microfloid test method).
Immerse the tablets in the liquid under test for a few seconds. Liquids can also be used to flush directly onto the surface of the microflotail. Culture the tablets in a tightened original packaging protective tube, test them with a thermostatic humidity box, and culture them for 2-5 days at 30/25 degrees C to check if the sample is contaminated with bacteria or fungi. The detection limit for this method is approximately 1CFU/cm2 or 100cfu/mL.
-mikrocount ® TPC (nutritional agar): used to detect bacteria. The temperature of 30℃ is suitable for bacterial growth. Usually 1-2 days of culture is enough for bacteria to grow.
-mikrocount® duo ( tiger red agar): for detecting fungi, including yeast and mold. The temperature of 25℃ is suitable for the growth of yeast and mold. Usually 2-3 days of culture is enough for yeast growth, 5-7 days for culture is enough for fungal growth.
Observe if culture surface has bacteria and fungus. If there are bacteria, UV sterilization is carried out and retested.
Dry membrane fungus test.
(Mold test GB/T 1741).
1, sterile sample paint in accordance with the product construction process for electrophoresis plate. The model requires a 5cm x 5cm square-size aluminum plate. Each sample has 4-6 models that are maintained in a constant temperature and humidity environment for more than 16 hours.
2, according to GB/T 1741 standard will need 9 experimental strains in the biosecurity cabinet with aseptic inoculation ring pick mold spores, inoculated on the potato-glucose medium (PDA), in 28 degrees C to 30 degrees C conditions to cultivate 7d To 14d, when the surface of the medium is full of mold spores, add 1mL sterile water, in the biosecurity cabinet with aseptic inoculation ring in sterile operating conditions gently scrape mold spores on the surface of mold culture, to make mold spore suspension.
3, the test model to be tested under ultraviolet light irradiated 30-60min, sterilization, to prevent the impact of pollution caused by the external environment. Pour about 20mL of nutrient salt agar medium into a sterile petri dish, and after the medium solidifies, 3 test samples and 3 control samples are placed in the center of the surface of the Petri dish containing the medium under sterile conditions. Apply 0.41mL to 0.61mL mixed mold spores to the surface of each test sample and control sample and medium surface with a sterile sprayer to moisten the entire test and control sample surface and medium surface. The inoculated test samples and control samples were placed in a constant temperature and humidity incubator, at a temperature of 25 degrees C to 30 degrees C, relative humidity is not less than 85% of the conditions of culture 7d after visual examination of the control sample mold growth, 3 control samples should have mold growth, otherwise the test is invalid, should be re-tested. If mold growth is visible on each control sample, the results are evaluated after the culture test sample and the control sample have been 28d. (The training period may be extended to 56d as agreed by the parties concerned).