Introduction to the technical content of the national standard GB/T 1741-2007 Paint Film Mold Resistance Determination Method

0 Introduction:
coatings in architectural decoration, with anti-corrosion and mold and other functions of new coatings in recent years has been rapid development. However, the corresponding paint testing standards have stopped, as far as the paint mold resistance testing standards, the existing GB / T1741-1979 (89) "paint film mold resistance determination method" since its promulgation in 1989, has been used to this day. The standard in the test time, test method, strain selection, equipment and mold rating and other aspects have not adapted to the development of the existing coatings industry
China
. The Guangdong Institute of Microbiology has formulated GB/T 1741-2007 "Paint Film Mold Resistance Determination Method" in accordance with the requirements of the "National Paint Pigment Standardization Committee (2006) Paint Marker (14)" document. The formulation of the new standard refers to the relevant international standards and absorbs the latest research results at home and abroad, compared with GB/T1741-1979 (89) "Paint film mold resistance determination method", GB /T 1741-2007 form complete, strong norms, bacteria selection can better represent the real use of the paint environment, test time more scientific, more perfect test methods, increased advanced test equipment, paint film carrier selection and coating preparation are scientific and reasonable, test conditions are strict, test results can truly reflect the paint film mold resistance.1 GB /T 1741-2007 main content and its preparation according to
111 main content
GB/T 1741-2007 includes the scope of application, normative reference documents, terms and definitions, test principles, test conditions, mold species and mixed mold spores (seeds) suspension preparation, inspection procedures, results observation of a total of 8 chapters.
112 according to the
11211 test time
GB / T1741 -1979 (89) set the test time of 14 days, in 14 days if the naked eye can not see mold growth on the surface of the paint film, the mold-resistant coating mold resistance is considered to be strong. However, mold reproduction is a very complex problem, if the test only culture 14 days, mold growth on the coating is still in its infancy, according to which the evaluation of mold effectiveness is often not accurate. Therefore, GB /T1741-2007 according to the long-term test results of this laboratory and learn from domestic and foreign test standards on the training time provisions, the mold-resistant test culture time was extended to about 28 days, so that the observed results are more accurate and reliable. The training time specified by this laboratory by reference to the international and domestic paint film mold resistance test standards (BS 3900: Part G6: 6 weeks or 12 weeks; ASTM D 5590-1994: 4 weeks; ASTM D 3273-00: 4 weeks; J IS Z 2911: 2000: 2 weeks or 4 weeks; GB /T2423116-1999: 4 weeks or 12 weeks), the paint film of different test times for mold resistance test comparison, in the selection of bacteria, inoculation, inoculation method, culture temperature, carrier and other conditions are consistent, to A, B, C 3 Different coatings as mold-proof test samples, D (without mold-proof agent blank latex paint), E (fibre filter paper, not mold-proof treatment), F (cotton cloth, not mold-proof treatment) as a control sample, the choice of Petri dish method, different test time comparison (test data see Table 1).
: The level of result determination is determined by the rating method specified in GB /T 1741-2007, and the result determinations involved in the following table are consistent with this.
analysis according to the comparative results of Table 1: the test after different culture time (2 weeks or 4 weeks), the good anti-mold effect of the sample has no obvious effect, and the anti-mold effect is not very good sample has a significant impact. At the same time, from table 1 culture after 1 week of results, the control sample D and F culture after 1 week long mold is not obvious, control sample E culture after 1 week long mold is most obvious. Table 1 also demonstrates why fiber filter paper is used as a control sample in the anti-mold performance test of paint film, instead of blank paint film as a control sample.
11212 Test Method
Gb /T 1741-1979 (1989) uses two experimental methods, A and B, in fact, the two methods belong to the same type, namely Petri dish method, this method is only applicable to small test samples. In order to adapt to different specifications of the test samples, GB /T 1741-2007 in the test method has been revised, in addition to petri dish testing method, but also added suspension method, small sample selection Petri dish testing method, large sample selection suspension method.
Suspension method: the sample to be tested after receiving bacteria suspended in a wet room (a certain amount of water in the closed box, the sample hanging above can not touch water), the wet chamber in a certain temperature environment, cultured after 28 days to observe the test results. Petri dish testing method: that is, the sample was placed in an inororated salt medium pan dish, after inoculation in a certain temperature and humidity environment, culture 28 days after observation of the test results. In this laboratory in the selection of bacteria, inoculation, inoculation method, culture temperature (28 degrees C), carrier (aluminum sheet) and other conditions are consistent, with pure C anti-mold latex paint as the test sample, fiber filter paper (not anti-mold treatment) as a positive control sample, while selecting the same paint test sample as a negative control (not inoculated), the petri dish method and suspension method of the experimental process and results were compared (see Table 2).
results of different test methods in Table 2
According to Table 2 analysis, there is no significant difference between the test results of Petri dishes detection and suspension. The anti-mold standards at home and abroad are used for both methods, GB/T2423116-1999, GJB150110-86, M IL-STD-810F-2000 and other standards using wet room suspension method, ASTM D 5590-1994, ASTM G21-1996 standard petri dish detection, J IS Z 2911:2000 has both suspension and Petri dish detection. Petri dish method advantages: suitable for small sample testing, each sample is relatively independent, do not interfere with each other, save space. Disadvantages: humidity control, flat dishes need more inorganic salt culture base to maintain sufficient humidity, otherwise the culture base dehydration dry cracking, humidity reduction and affect the test; The advantages of suspension method: suitable for the test of large samples, as long as there is enough water in the box, its relative humidity can be constant. Cons: When the same set of samples is placed in the same wet box, it is easy to interfere with each other, and multiple samples will need multiple wet boxes and take up a lot of space for simultaneous testing.
11213 Instruments and equipment
compared to GB/T 1741-1979 (1989), GB/T 1741-2007 added thermostat constant humidity culture box, hygrometer, mold spore spray tank, biosecurity cabinet, centrifuge, refrigerator and other test equipment to ensure the accuracy and safety of the experiment. The constant temperature and humidity culture box is essential in the culture process of mold species and experimental samples, and the control of temperature and humidity determines the success or failure of the experiment. Wet steam sterilization pot, dry heat sterilization box is different equipment and experimental supplies for sterilization: test tubes, beers, conical bottles, piped pipes, glass flats, etc. with dry heat sterilization box 160 to 170 degrees C sterilization 2 h, medium, water, culture fluid, waste treatment and other wet and hot steam sterilization pot sterilization. When a microscope helps to observe test results, the determination of trace growth or non-growth must be observed through a microscope. Centrifuges are designed to better purify the organic culture components on the spores and purify the spores, as it is possible to bring in a small amount of organic cultures or mycelium when washing the strains from the slope, which, if not removed, will seriously interfere with the results of the experiment. Because mold has great harm to the environment and personnel, if not careful may lead to microbial hazards, so the standard strictly control the impact of mold on the environment, in addition to the requirements of a certain microbial operation experience of personnel test operation, but also requires mold spore spray box, biosecurity cabinet and other equipment, conducive to environmental protection and personnel safety. Refrigerators are designed to better preserve mold species. Trace elements of inorgeable salt media require a high-precision balance (accuracy 0101 g) weighing. Thermometers and hygrometers are designed to better monitor the temperature and humidity of bio-culture tanks. Glass or plastic closed containers are used for hanging experimental culture, glass or plastic closed containers containing a certain amount of water, made into a wet room, the sample to be tested after inoculation hanging in the wet chamber, to ensure that the sample during the test required humidity.
11214 paint film preparation
compared to GB /T 1741-1979 (89), GB /T 1741-2007 regulations can be based on the actual application of the test sample to choose the paint film carrier, such as glass, aluminum plate, wood sheet, galvanized (or tinned) iron sheet, filter paper, etc. , and the size of the carrier, the thickness of the carrier has been standardized requirements, the application of the situation has also made corresponding requirements. The choice of carrier is more extensive, which is more applicable in the actual experimental process. The laboratory tested and compared the mold resistance of different thickness paint films, and the experimental data were found in Table 3.
3 effect of different paint film thickness on the test results
the experimental results show that the paint film thickness has no significant effect on its mold resistance. Therefore, in the preparation of paint film, if the first application is thick and thin uniform, it may not require the second application, if the first application is uneven, hollow or uneven, it is necessary to apply again, until the test requirements can be met.
11215 Test bacteria
depending on the use of internal and external wall coating environment is different, microbial contamination of the species is not the same characteristics, GB / T 1741-2007 reference to other paint film mold resistance test standards at home and abroad in the selection of strains (see Table 4), according to the paint film and the environment isolated mold The type (or genus) of bacteria, GB / T1741-1979 (1989) selected species have been revised, so that the choice of bacteria more representative, more in line with the actual use of the environment, taking into account that the inner wall paint film and the outer wall paint film use environment is not the same, so the inner and outer wall paint film selection is also different. GB/T 1741-2007 specifies the concentration of spores in the spore suspension and specifies the amount of spray sprayed on the paint film. GB/T 1741-2007 is more operational, more standardized and more advanced.
(1) Species selection
(1) relevant studies at home and abroad
According to relevant literature at home and abroad, the most common mold affecting lacquer film is mainly aspergillus sp1 and penicillin (Penicillium sp1), followed by short infarction genus (Aureobasidium sp1), rhizophydium sp1, Chaetom ium sp1, trichoderm a sp1, and cross-chain spores (A lte2naria sp1). The following literature documents the main types of mold that have been isolated from the paint film to date. In "Microbial Disasters and Their Prevention Techniques", Mei Jing pointed out that the molds that are prone to contamination paint are: on the paint film coated with paint, it is also easy to grow buds and short terrier molds (Aureobasidium pullulans), black music Mold, Cla2dosporium herbarum, Rhi1nigricans, group stem mould (Phom a glom erata), chain spores (A lt. A lternats) . . . . . . . . . . . . . . . . . . . . . . Japan has conducted sampling surveys of interior decoration materials in 260 locations, and the representative strains of mold obtained are: Cladosprium, Acrem onium, penicillin, woody mold, cross-chain spores, ascormycin, and gold mold.
Ma Zhenxuan in the "microbial corrosion of latex coating and its prevention technology" said that the coating after coating on the coating film breeding microbial mold is mainly: germination short infarction mold, la leaf bud mold, black asfilm, black root mold, group stem mold, chain spores. Ouyang Yousheng and so on according to the 10 cities (counties) in Guangdong Province, 26 food (drink) workshop wall pollution sampling separation, the advantages of mold genus are: Rhizopusarrhizus, asp. sydow ii), chain spores, aflatoxin (Asp. f lavus), sprouting short terrier mold, semi-thromycin sp. ) , rotting mold genus (Hum icola sp. ) , huge asp. giganteus), black penicillin, black root mold, meat-colored asphalt (Asp. carneus), green wood mold (Trichoderm a viride), orange penicillin (Penicillium citrinum), rope penicillin (Penicillium funiculo2sum), megan mold (Rhi. oryzae), common penicillin (Pen. citreo - viride), production of penicillin (Pen. chrysogenum), etc. The most common of these are the genus penicillin and penicillin genus, followed by the genus short terrier mold, genus root mold, genus mold, genus wood mold and cross-chain spore genus. Among them, chain spores are easily separated into particularly humid workshops such as breweries and beverage plants.
Zhong Yudong pointed out in "The application of anti-mold agent/anti-algae agent in latex paint", the common bacteria exposed to the outer wall latex paint environment are: chain spores, aflatoxin, black aspergycin, aspergillus ustus, la leaf bud mold, germinated short terrier mold, orange penicillin, Paukukim yces cariotl, S tachybotrys. Wang Yuxuan in the "water-based architectural coatings in the choice of mold inhibitors" article mentioned that water-based coatings after coating may grow mold on the coating film mainly black curvature, penicillin, root mold and so on.<