Evaluation of the Influence of Coating Amount of PVDC Coating on Material Barrier Property
Abstract: The coating of PVDC layer on the surface of materials is a common method to improve the barrier properties of materials. In this paper , the oxygen permeability of membrane materials with different coating amounts of two PVDC coatings is tested to further study the barrier of materials by different PVDC coatings. Sexual influence, and introduced the test principle, equipment parameters and scope of application, test process, etc., to provide a reasonable evaluation method for material modification or improvement of barrier properties after the process.
Key words: PVDC coating film, K coating, coating amount, barrier property, oxygen permeation, differential pressure gas permeation tester
1 , meaning
Polyvinylidene chloride (PVDC) is a polymer material with high symmetry, high crystallinity, high barrier properties, etc., but its molding processability is poor. Generally, it needs to be copolymerized with other monomers, using injection molding and extrusion. Processing by methods such as extrusion, compounding, coating, and blow molding, in which a K film formed by coating one or more layers of PVDC on various film substrates is relatively common. Commonly used coating substrates include PP , PET , PA , PE, etc., because the presence of PVDC greatly improves the barrier properties of the film as a whole, enhances the barrier properties of the film to gas, as well as the aroma and oil resistance, so it is widely used. Packing moon cakes, biscuits, tea, cakes, chocolate, dairy products, meat products, aquatic products, condiments and other foods. The barrier property of the K film mainly depends on the PVDC layer, so the coating amount of the applied PVDC layer is an important factor affecting the barrier property of the K film.
Figure 1 K film packaging application example
2 , test samples
In this test , K film materials with PVDC coating amounts of 2 g/m 2 and 4 g/m 2 were used as test samples, and the oxygen permeation amounts of the two samples were tested separately.
3 , the test basis
The test principle of oxygen permeation of film materials includes pressure difference method and isobaric method. This paper uses the principle of differential pressure method to test. According to the standard GB/T 1038-2000 , the plastic film and sheet gas permeability test method is pressed. Difference Law.
4 , test equipment
In this paper, the VAC-V2 differential pressure gas permeation instrument independently developed by Jinan Languang Electromechanical Technology Co., Ltd. is used to test the oxygen permeation of the sample.
Figure 2 VAC-V2 differential pressure gas permeation meter
4.1 Test principle
The principle of differential pressure method means that a certain pressure difference is maintained on both sides of the sample, and the gas permeability of the sample is obtained by testing the pressure change caused by gas permeation. The clamped sample divides the test chamber of the device into upper and lower chambers, the upper chamber is filled with test gas, and the lower chamber is vacuumed to form a low pressure environment. The gas in the upper chamber is tested under the pressure difference. The sample penetrates into the lower chamber, and the pressure change in the low pressure chamber is monitored by the pressure sensor. When the penetration reaches equilibrium, the parameters such as the gas permeation amount of the sample are calculated according to the change of the pressure in the low pressure chamber with the penetration time. This method can test the permeability of a variety of gases.
4.2 Scope of application
(1) This equipment is specially used for testing the gas permeability, permeability coefficient, solubility coefficient and diffusion coefficient of various film and sheet samples at various temperatures. Films include various plastic film, paper-plastic composite film, co-extruded film, aluminized film, aluminum foil, aluminum foil composite film and other film-like materials; sheet materials include various engineering plastics, rubber, building materials and other sheet materials, such as PP Sheet, PVC sheet, PVDC sheet.
(2) This equipment can also be extended to aerospace materials, paper and paperboard, paint film, fiberglass cloth, glass fiber paper, cosmetic hose sheets, various rubber sheets and other materials for gas permeability testing.
(3) This equipment is suitable for the permeability test of various gases, such as oxygen, carbon dioxide, nitrogen, helium, air, etc.
(4) This equipment can meet a variety of national and international standards, such as ISO 15105-1 , ISO 2556 , GB/T 1038 , ASTM D1434 , JIS K7126-1 , YBB00082003 and so on.
4.3 Equipment parameters
- 0.05 ~ 50,000 cm 3 / (m 2 · 24h · 0.1MPa) , vacuum resolution can reach 0.1 Pa ; temperature control range is 5 °C ~ 95 °C , temperature control accuracy is ± 0.1 °C ; humidity control range is 0% RH , 2% RH ~ 98.5% RH , 100% RH , humidity control accuracy is ±1% RH , which can meet the testing requirements of customers under different test conditions; three completely independent test chambers can test three identical or different tests simultaneously The data can be fitted at any temperature to easily obtain the test results under extreme test conditions; after modification, the device can also support the testing of toxic gases and flammable and explosive gases; provide standard film for rapid calibration and ensure Detect the accuracy and versatility of the data; support the Lystem TM laboratory data sharing system, unified management of test results and test reports.
5 , the test process
5.1 coating amount was 2 g / m K film sample 2
(1) Cutting sample
Three specimens with a diameter of 97 mm were cut from the surface of the sample.
(2) Loading
A layer of vacuum grease was applied, were placed in the test chamber 3 surrounding the test area of 65 mm diameter filter paper, the sample was attached to the test chamber, the sample gently press to remove air bubbles, The specimen is clamped by clamping structure .
(3) Test
Set the test temperature, test humidity, sample thickness and other parameters information, open the vacuum pump, water bath temperature control device, click the start test option, the test begins. The equipment is automatically tested according to the set parameters and the test results are displayed after the test is completed.
5.2 coating amount of 4 g / m K film sample 2
Test according to the procedure in 5.1 .
6 , test results
The test values of the K film samples with a coating amount of 2 g/m 2 tested in this test were 7.85 cm 3 /(m 2 ·24h·0.1MPa) , 7.69 cm 3 /(m 2 ·24h·0.1MPa) , 7.99 cm 3 /(m 2 ·24h·0.1MPa) , the average value is 7.84 cm 3 /(m 2 ·24h·0.1MPa) ; the test value of the K film sample with the coating amount of 4 g/m 2 is 4.79 respectively. Cm 3 /(m 2 ·24h·0.1MPa) , 4.83 cm 3 /(m 2 ·24h·0.1MPa) , 4.67 cm 3 /(m 2 ·24h·0.1MPa) , average value 4.76 cm 3 /(m 2 · 24h · 0.1MPa) .
7 , conclusion
From the test results, a deviation of 3 samples each sample test values are small, high precision, the coating amount of 4 g / m 2 K oxygen permeable membrane coating amount was significantly lower than the amount of 2 g The K film of /m 2 indicates that the former has a high oxygen barrier property, and the factors affecting the K film barrier property of the same substrate include the coating method and the coating process, in addition to the coating amount of the PVDC layer, The two samples were tested and produced by the same manufacturer. The influence of the coating method and the coating process was small. The difference in oxygen barrier was mainly related to the coating amount. From the perspective of the test process, the operation was simple and the equipment was highly intelligent. In addition to testing the oxygen permeation, the device can also be used for the permeation behavior test of various gases such as nitrogen, air, helium, carbon dioxide and sulfur hexafluoride, and the test efficiency is high, which is a cost-effective testing equipment. Labthink is looking forward to enhancing technical exchanges and cooperation with enterprises and institutions in the industry.
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