The Effect of Flexing on Barrier
The barrier properties of most materials degrade as the material is flexed. As a result, handling of materials during loading, packing, and distribution can have a significant effect on the barrier provided by the package and ultimately the shelf life of the product.
When choosing barrier materials, concern is often expressed regarding the ability of silicon oxide coatings to maintain their barrier when flexed. The reality is that most grades perform favorably when compared to aluminum foil and metallized composites. For more demanding applications, there are grades available that provide tremendous flex-crack resistance.
The table below illustrates the effect of flexing on a series of barrier composites.
The only difference between the composites is the source of the barrier. All consist of 48 gauge (12µm) oriented polyester, a barrier layer, and 0.002″ (50µm) linear low density polyethylene. Samples were flexed ten times using a Gelbo Flex Tester and the oxygen transmission rates evaluated before and after flexing
|Barrier After Flexing|
|48 ga oPET / 35 ga Foil / 2 mil LLDPE||0.03||3.2|
|48 ga oPET / Met / 2 mil LLDPE||0.1||0.7|
|48 ga oPET/ ClearFoil®A / 2 mil LLDPE||0.04||0.5|
|48 ga oPET/ ClearFoil®F / 2 mil LLDPE||<0.003||<0.003|