This paper describes the performance of vacuum metallized PET film one by one from its thickness, uniformity, fastness and physical and mechanical properties, as well as the measurement methods of each index for reference.
1. Thickness of aluminum coating
The following three methods are generally used to measure the thickness of aluminum coating.
The first is the optical density method, which measures the density of light passing through the metallized film. It is convenient and accurate to measure the thickness of aluminum coating by optical density, and the measurement results are not easily affected by the surface oxide layer. The optical density is related to the wave length of incident light.
The second is to use the surface block resistance measurement. This method is simple and practical. Generally, the surface resistance corresponding to the thickness of aluminum layer is 1 ~ 2. Sampling or width 1cm long, 10cm resistance value between 1 and 20. When the coating is just rolled down, the surface oxidation of the aluminum layer is less and the measurement is more accurate.
The third method is visual estimation. If two layers of metallized film are stacked together to look at the fluorescent lamp or the sky, the invisible light shall prevail, and the thickness of the coating shall be more than 400 μ m, but this method is easily affected by the vision of the eyes. When the metallized film is pasted in front of the eyes to watch, the pupil of the eyes will be adjusted with the darkening of the light, and the invisible light will be seen after the pupil adjustment.
2. Uniformity of aluminum coating
Take 8-10 samples with the specification of 100mm × 100mm horizontally and equidistant from the tested sample, measure the resistance value of the block with the resistance measuring instrument, and take the average value of its calculation, that is, the coating resistance of the sample, the upper and lower deviation of the resistance value, and the deviation of the resistance layer, which actually reflects the uniformity of the aluminum coating.
3. Fastness to metallized
The fastness of metallized is generally tested by tape. When the adhesive tape is used to determine the fastness of the metallized layer qualitatively, stick the adhesive tape about 15cm long on the metallized surface and press it flat with fingers. Then press the sample with one hand, and peel the adhesive tape with the other hand at a constant speed. Use the light box with strong light to check the aluminum layer falling off and transferring.
Another method to determine the fastness of aluminum coating is used for pet aluminum coating. Heat seal a specially prepared test film and pet aluminum coating film according to certain heat sealing conditions, then peel off the sample with a tensile testing machine, measure the peeling force and check the transfer of aluminum layer in the heat sealing area.
4. Physical and mechanical performance index