Test methods for properties of plastic film of the

Test method for the performance of plastic film of packaging materials (Part 2)

barrier performance

as a packaging material, plastic film needs to protect its contents and block the impact of the external environment on commodities. Such as moisture-proof, oxidation proof, oil proof, odor proof, etc

1. There are many test methods for moisture resistance. The commonly used test methods are GB/t1037-1988 "test method for water vapor permeability of plastic films and sheets cup method". This method is applicable to plastic films, composite plastic films, sheets, artificial leather and other materials. Under the specified temperature and relative temperature of the tested sample, seal the sample with mixed paraffin and beeswax on the moisture permeable cup, fill the cup with a certain amount of desiccant, and maintain a certain water vapor pressure difference at both ends of the sample. Weigh the weight change of the sealed sample before the test and after humidification, and its increment is the water vapor transmission

gb/t16928-1997 "test methods for packaging materials moisture permeability" this standard is equivalent to the 3030 in the American federal standard fed-std-101. This method is applicable to paper plastic composites, etc. The test is to package the desiccant in the sample, expose the tested surface to the test environment, and weigh the increment of weight change before and after the test after a certain period of time

GB/t6981-2003 "test method for moisture permeability of flexible packaging containers" is applicable to sealed flexible packaging containers. Put the desiccant into the container that wins market share by relying on technical resources and customer advantages, seal it, and then place it under the specified temperature and humidity conditions. The amount of weight gain of the sample after a certain period of time, that is, the amount of water vapor transmission

the disadvantages of the above methods are that the test time is long and is greatly affected by the environment. Especially in recent years, with more high barrier plastic packaging materials, the accuracy of some methods is obviously insufficient. Now our laboratory has introduced the moisture permeability tester of m0con company of the United States and diocesan company of Hong Kong. M0con adopts American ASTM Standard Test Method for water vapor transmission rate through plastic film and Sheeting Using a modified infrared sensor. The moisture permeability standard of Hong Kong extraction company is developing a test method standard, which will soon be used in the test of water vapor permeability of materials

2. Gas barrier performance

at present, the commonly used permeability test method in China is GB/t1038-2000 "test method for gas permeability of plastic films and sheets - differential pressure method". This standard is equivalent to ISO 2556:1974 and is applicable to the determination of plastic films and sheets. The test instrument consists of a low-pressure chamber and a high-pressure chamber. Stick the sample between the high-pressure chamber and the low-pressure chamber, vacuum the two chambers with a vacuum pump in the closed chamber, and then fill the high-pressure chamber with a test gas of atmospheric pressure (0.1MPa). The gas transmission is calculated by measuring the pressure increment in the low-pressure chamber. According to the estimation of uacj, the laboratory also introduced the instruments of m0con company in the United States. The standard of American ASTM "design: D (reapproved 1988) stand test method for oxygen gas transmission rate through plastic film and Sheeting Using a Coulometric Sensor" is adopted. Hygienic performance

the hygienic performance of packaging materials has attracted more and more attention. In international trade, many countries prohibit materials containing harmful substances from entering the market, such as the content of heavy metals, solvent residues and so on, which are restricted by all countries. China also has many regulations on the hygienic properties of food packaging materials. The commonly used inspection methods and standards for the hygienic performance of plastic packaging materials are: gb/t5009 Analysis method of hygienic standard for polyethylene resin for food packaging, gb/5009 Analysis method of hygienic standard of polystyrene resin for food packaging, gb/5009 "Analysis method of hygienic standard for polyethylene, polystyrene and polypropylene ethylene molded products for food packaging", gb/5009 Analytical method for hygienic standard of melamine molding products for food packaging. These standards mainly stipulate the experimental methods for the organic, inorganic, heavy metals and decolorization of food packaging materials. Soak the side material in water, ethanol, acetic acid and n-hexane at a certain temperature in a certain proportion for a certain time to obtain the soaking solution. These liquids respectively simulate the water, vinegar, alcohol and oil that packaging materials contact

after soaking, the dissolved organic content of the sample is generally expressed by measuring the consumption of potassium permanganate

after evaporation, the content of the residue dissolved from the packaging material can be weighed out

qualitative experimental methods are generally used for heavy metals (calculated by lead) in food packaging materials. The experimental principle is that the heavy metal (with lead meter) in the soaking solution reacts with sodium sulfide to form yellowish brown lead sulfide in the acidic solution, which is compared with the standard color sample. If it is deeper than the standard color sample, it means it does not meet the standard

the decolorization test is to observe that the soaking solution of the sample should not be stained with color, and wipe the surface of the packaging material or container with cotton stained with cold meal oil, ethanol and other solvents, and the cotton should not be stained with color to test whether the sample is decolorized

some solvents will remain in the manufacturing and printing process of packaging materials. Gb/t "cooking resistant composite films and bags" and gb/t "biaxially oriented polypropylene (BOPP)/low density polyethylene (ldper) composite films and bags" stipulate the determination of residual solvents such as acetone, isopropanol, ethyl acetate, toluene, xylene and other solvents in the sample by gas chromatography

refer to gb/t4859.2 for the residue of organic pesticides in packaging materials and the content of 20 kinds of organic pesticides, such as dichlorvos, phosphine, dimethoate, phosphorus quinolate, etc 3 . 4 . 5 . 6 . 7 . 8.9 . 10 . Conduct the test

other properties

other performance test methods of plastic film for packaging include optical properties, such as light transmittance, haze. Light transmittance refers to the ratio of luminous flux passing through the sample to the luminous flux entering the sample. Haze refers to the ratio of luminous flux passing through the sample and away from the incident angle to the transmitted luminous flux. Gb/t transparent plastic water transmittance and haze test methods are commonly used at present

as a packaging material, plastic film often needs to be printed, which requires surface treatment, such as corona treatment, to achieve a certain surface tension gb/t test method for wetting tension of plastic film and sheet "Lubrizol currently has a laboratory and factory in Songjiang, Shanghai, which uses the originally prepared test solution with different tension, commonly known as" dyne solution "to test the surface tension of samples

plastic film is affected by ambient temperature, which often causes size changes. Gb/t plastic linear expansion coefficient measurement method is a method to test the linear size change of materials under certain temperature conditions

qb/t plastic water absorption test method is to express the amount of water absorption by weighing the change of the weight of the material before and after immersion

the cooking resistance of plastic film packaging bags gb/t stipulates the test method of heat resistance and medium resistance. The bags are respectively filled with sodium chloride, ethanol and vegetable oil that simulate contact with salt, acid, alcohol and oil in food. After sealing, observe the integrity of the packaging bags after high-pressure and high-temperature cooking, or the performance changes of the test materials before and after the test

in a word, there are many testing methods for plastic film, each of which has certain applicability, and there are certain uncertainties in various test results, including methods, instruments, personnel, environment, samples, reagents, etc. Therefore, the selection of method standards must be carefully studied and verified

source: zhuochuang information