Abstract: The moisture barrier performance is an important factor affecting the performance of thermal silica gel. This paper introduces a test method for the moisture resistance of a thermal silica gel sheet by testing the water vapor transmission rate of a brand of thermal silica gel sheet. The test principle, the parameters of the W3/330 water vapor transmission rate test system, the scope of application, and the description of the test process provide a reference for the company to test the moisture resistance of the thermal silica film.
Key words: moisture barrier performance, water vapor transmission rate, thermal silica sheet, water vapor transmission rate test system, electrolysis
1 , meaning
The thermal conductive silica gel sheet is a heat conductive medium material synthesized by using silica gel as a base material and adding a metal oxide or the like, and the material is formed by filling the gap between the heat source and the heat sink. Good heat dissipation path. Thermal silica gel sheets are widely used in the LED industry, power supply industry, communication industry, automotive electronics industry, home appliance industry, etc., such as the connection between the notebook motherboard chip and the heat sink. Since the internal components of electronic products are sensitive to water vapor, preventing internal moisture during use is a prerequisite for ensuring the service life and performance of the product. When the thermal conductive silicone sheet is used between the electronic chip and the heat sink, The electronic chip is sealed in a closed environment, and the thermal conductive silicone sheet as a part of the sealing material, its water vapor barrier performance will directly affect the amount of water vapor that the electronic chip can contact. Therefore, the selection of a heat-conductive silicone sheet suitable for moisture barrier properties is important for preventing moisture in electronic products.
Figure 1 Thermal silica film
2 , testing basis
At present, the test methods for water vapor transmission rate of materials are mainly divided into cup method, electrolytic sensor method, infrared sensor method and humidity sensor method. In this paper, the water vapor transmission rate of thermal conductive silica gel sheet is tested by electrolytic sensor method. The method standard according to GB/T 21529-2008 " Electrolytic sensor method for the determination of water vapor transmission rate of plastic film and flakes ".
3 , test samples
The sample tested in this test is a brand of thermal silica film.
4 , test equipment
This paper uses the W3/330 water vapor transmission rate test system as the test equipment, which is independently developed and produced by Jinan Languang Electromechanical Technology Co., Ltd.
Figure 2 W3/330 water vapor transmission rate test system
4.1 Test principle
After the sample is clamped into the osmotic chamber, the sample divides the osmotic chamber into a low-humidity chamber and a high-humidity chamber. The dry nitrogen gas flows in the low-humidity chamber, and the nitrogen gas flowing in the high-humidity chamber is nitrogen gas having a certain humidity. The water vapor that has passed through the sample from the high-humidity chamber into the low-humidity chamber is carried into the electrolytic cell by the nitrogen gas. The structure of the electrolytic cell is usually: there are two spiral metal electrodes inside, the electrodes are mounted on the inner wall of the glass capillary, and the surface of the electrode is coated with a thin layer of phosphorus pentoxide. Nitrogen gas is passed through the glass capillary tube, and the water vapor carried by it is quantitatively absorbed by the phosphorus pentoxide. Water vapor is electrolyzed into hydrogen and oxygen by applying a certain DC voltage to the electrodes. Based on the value of the electrolysis current, the amount of water vapor per unit area per unit area is calculated.
4.2 Scope of application
(1) This equipment is suitable for water vapor transmission rate test of plastic sheet, film, paper, cardboard and its composite materials, containers and so on. Sheets include various engineering plastics, rubber, building materials and other sheet materials, such as PP sheet, PVC sheet, PVDC sheet, etc.; paper, cardboard samples, such as cigarette coated aluminum paper, paper aluminum-plastic composite sheet Materials; film materials include various plastic film, paper-plastic composite film, co-extruded film, aluminized film, aluminum foil, aluminum foil composite film, glass fiber aluminum foil paper composite film, etc.; containers include plastic, rubber, paper, paper and plastic Bottles, bags, cans, boxes, barrels made of composite, glass, metal, etc., such as Coke bottles, peanut oil barrels, Tetra Pak packaging, vacuum packaging bags, metal three-piece cans, plastic cosmetic hose packaging, toothpaste hose packaging , jelly cups, etc.
In addition, the device can be used to test the water vapor transmission rate of special packaging such as medical packaging, automobile fuel tank, battery plastic casing, plastic pipe, solar backing plate, etc.
(2) This equipment can meet a variety of national and international standards, such as GB/T 21529 , ISO 15106-3 , DIN 53122-2 , YBB 00092003 .
4.3 Equipment parameters
- Test range: film test 0.001 ~ 40 g / (m 2 · 24h) , and can be extended to 0.01 ~ 1000 g / (m 2 · 24h) , container test 0.0001 ~ 0.2 g / (pkg · d) ;
- Number of samples: 1 ~ 3 pieces (data are independent);
- Resolution: film 0.001 g / (m 2 · 24h) , container 0.00001 g / (pkg · d) ;
- Test temperature range: 15 °C ~ 55 °C , temperature control accuracy ± 0.1 °C ;
- Test humidity range: 0% RH , 35% RH ~ 90% RH , 100% RH , humidity control accuracy ± 1% RH ;
- The system zui can support 10 instruments in parallel connection, and establish an efficient system for simultaneous testing of 30 samples;
- It can be combined with the oxygen transmission rate test system to form a hybrid test system, which is controlled by a computer to achieve an efficient and convenient test method for simultaneous testing of water vapor and oxygen transmission rate;
- Support Lystem TM laboratory data sharing system to manage test results and test reports.
5 , the test process
(1) Cut 3 pieces of the sample with a dedicated sampler .
(2) The three samples were clamped in a test chamber device 3, and clamped to ensure good sealing of the sample does not leak.
(3) Set the sample name, sample thickness, test temperature, test humidity and other parameters, click the test option, the test begins.
(4) Start the gas source, adjust the nitrogen flow rate and the nitrogen pressure to make the test chamber humidity and nitrogen flow reach the specified value.
(5) After the test is over, the instrument automatically calculates and displays the test results.
6 , test results
The water vapor transmission rates of the three samples tested in this test were 8.034 g/(m 2 ·24h) , 7.981 g/(m 2 ·24h) , and 8.116 g/(m 2 ·24h) , respectively. It is 8.044 g / (m 2 · 24h) .
7 , conclusion
The water vapor transmission rate of thermal silica gel sheet is one of the important factors affecting the service life and performance of electronic equipment. In this paper, the water vapor transmission rate of a brand of thermal silica gel sheet is tested by electrolytic sensor method. The test operation is simple and the equipment is intelligent. The degree of chemicalization is high, and the test results show that the sample has good uniformity and high test accuracy. Jinan Languang Electromechanical Technology Co., Ltd. is a high-tech enterprise specializing in the R&D, production and testing services of packaging testing equipment. The existing equipment can test the barrier properties of packaging materials on oxygen, water vapor, nitrogen, air, carbon dioxide and other gases. Exhibit performance, puncture resistance, smoothness, impact resistance, heat sealing performance, sealing performance, solvent residue, total migration and other performance indicators . The more you understand, the more you trust! Labthink is looking forward to enhancing technical communication and cooperation with enterprises and institutions in the industry!
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