I often hear the questions: How does metallizing affect the yield or basis weight of flexible film? What is the thickness of aluminum applied? Even though vacuum metallizing can dramatically improve barrier values, the layer of metal is so thin that it does not alter the yield or mechanical properties of the film.
Vacuum metallizing is a process where an alloy, such as aluminum, is melted and vaporized onto a receptive surface. Vacuum deposition takes place in a chamber under pressure well below atmospheric pressure. Unwind and rewind stations mounted in the chamber allow the film to pass from unwind to rewind over the active boat bed area. The aluminum is melted at 1500 degrees celsius and forms a vapor cloud above the boat bed. As the substrate passes over this active area, a thin layer of aluminum is deposited onto the film, creating a barrier layer.
The aluminum thickness is measured in angstroms (Å), a unit of length equal to 10−10 m (one ten-billionth of a metre) or 0.1 nanometers (nm) and typically represents less than 0.1 percent of the base film. Generally, metal deposition in packaging applications ranges from 30.5 Å – 500 Å (3.5 – 50 nm).
Metallizing a film typically increases barrier values 10-fold over non-coated/non-metallized film, so many people are surprised to learn that such an remarkable improvement does not change the yield.
See chart below for barrier values comparing clear PET film and other metallized and coated films.
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