What Are Factors Affecting Barrier Properties Of Polymers For Packaging?
Barrier can be influenced by many factors including the type of material, thickness, orientation, humidity, defects, processing, and crystallinity. The barrier is directly proportional to thickness for typical film gauges. It is important to remember that coated films such as metallized PET are actually a composite structure. For metallized films, the thickness of the metal, expressed as optical density, is the determining factor. Thick foil is often used for its excellent barrier properties. An increase in temperature will typically increase the permeation of a gas. Humidity can strongly effect barrier properties. For example, oxygen permeation through ethylene vinyl alcohol is strongly effected by moisture while high density polyethylene is not strongly effected by moisture. For metallized films, it is important that the metal not be damaged or attacked by the product. Orientation has the same effect as increasing crystallinity. As a result, oriented PET has better barrier properties
