ã€Chinese Packaging Network News】 vacuum aluminum coating, an important material for flexible packaging, this article from its thickness, coating uniformity, fastness and physical and mechanical properties and other indicators one by one about its performance, and the measurement methods of each index.
1, aluminum film thickness
Aluminizing film thickness measurement generally uses the following three methods.
The first is the optical density method, which is measured by the density of light transmitted through the aluminized film. The advantage of measuring the thickness of the aluminized layer with optical density is convenient and accurate, and the measurement result is not easily affected by the surface oxide layer. The value of the optical density is related to the wavelength of the incident light.
The second is the use of surface sheet resistance measurements. This method is simple and practical, the general aluminum layer thickness corresponding to the surface resistance is generally 1 to 2. Sampling or width 1cm long, 10cm resistance value between 1~20. When the coating is rolled down, the surface of the aluminum layer is less oxidized and the measurement is more accurate.
The third method is visual estimation. If two layers of aluminized film are laminated together facing the fluorescent lamp or looking at the sky, the invisible light will prevail, and the thickness of the plating layer should reach more than 400 Ã…. However, this method is easily affected by the eye vision, when the aluminized film When affixed in front of the eyes, the pupils of the eyes will be adjusted as the light becomes darker. The rays that are not seen originally will be visible after the adjustment of the pupils.
2, the uniformity of the aluminized coating
Take 8 to 10 samples of 100 mm×100 mm in size along the horizontal direction of the sample to be measured, measure the resistance of the block with a resistance meter, and take the arithmetic average, which is the coating resistance of the sample. It is possible to calculate the deviations of the resistance values ​​above and below and the resistance of the resistance layer, which actually reflects the uniformity of the aluminum plating layer.
3, aluminum fastness
Aluminium fastness is generally measured with tape. When the adhesiveness of the aluminized layer was qualitatively determined with an adhesive tape, an adhesive tape of about 15 cm in length was attached to the aluminized surface and flattened with a finger. Then squeeze the sample with one hand and peel the adhesive tape evenly in the other hand. Use a light box with a light to check the transfer of the aluminum layer.
Another method for determining the fastness of the aluminized layer is used for the PET aluminized film. A specially prepared test film and a PET aluminized film were heat-sealed according to a certain heat sealing condition, and then cut with a tensile tester after cutting, the peeling force was measured, and the transfer of the aluminum layer in the heat seal area was examined.
4, physical and mechanical performance indicators
The physical and mechanical properties of common aluminized films are shown in the table below.
